Deuterated perovskite for room temperature spin device

Domain: neuroscience
Published: 2026-04-07
Editorial outcome: minor_revision

Abstract
Organic-inorganic hybrid perovskites (OIHPs) offer a promising alternative, combining strong spin-orbit coupling, high carrier mobility, and tunable optoelectronic properties. However, their potential for spintronic applications has been constrained by rapid spin relaxation, often attributed solely to the inorganic sublattice. Here, we demonstrate room-temperature spin transport in hybrid perovskites enabled by isotope engineering. Substituting hydrogen with deuterium in methylammonium lead iodide effectively suppresses hyperfine interactions (HFI), leading to a 2.6-fold increase in spin lifetime. As a result, CD₃ND₃PbI₃ exhibits a magnetocurrent (MC) ratio of 17.5% at room temperature, whereas conventional CH₃NH₃PbI₃ spin-valve devices show negligible MC response. A spin photovoltaic effect is also observed under ambient conditions, revealing a coupling between optical excitation and spin-polarized transport, and pointing toward new opportunities for light-addressable spintronic functionality. These findings not only revise the fundamental understanding of spin relaxation in hybrid materials, but also establish isotope engineering as a powerful strategy to access room-temperature spin functionality.

Introduction
Spintronics is a transformative field in post-Moore's law information technology, offering advantages such as low power consumption, high-speed operation, and non-volatility, which enable more efficient data storage and processing techniques1–4. However, achieving stable spin polarization and efficient spin transport at room temperatures remains a considerable challenge5–9. Among emerging materials, OIHPs have garnered significant interest in spintronics due to their strong spin-orbit coupling (SOC), minimal defect states, and solution-processability10–13. Compared to conventional semiconductors, perovskites exhibit extended spin diffusion lengths and superior spin manipulation, positioning them as promising candidates for next-generation spintronic applications, such as spin optoelectronics and quantum computing14–18. Nonetheless, the rapid spin relaxation inherent in these materials restricts their practical implementation in devices. Achieving precise control over spin dynamics and realizing efficient spin transport at room temperature in perovskites is essential to advancing this field.

A prevailing assumption in the field is that spin transport in hybrid perovskites is governed primarily by the inorganic Pb–I sublattice19, with organic cations having a minimal effect on carrier transport as well as spin dynamics. This perspective arises from the strong spin-orbit coupling (SOC) of Pb atoms, which is believed to dominate spin relaxation through Elliott-Yafet and D’yakonov-Perel’ mechanisms20–24. The role of organic cations, such as HFI of hydrogen, has been largely overlooked25–27. In fact, magnetic interactions can mediate long-range spin coupling28,29, indicating that the organic cation sublattice may still influence spin dynamics, even though it does not directly participate in carrier transport. This oversight has hindered progress in understanding the complete spectrum of spin relaxation mechanisms in OIHPs, leaving the contribution of the organic sublattice to spin dynamics largely unexplored.

In this work, we demonstrate that efficient spin transport in hybrid perovskites can be realized at room temperature by addressing a previously overlooked relaxation pathway—HFI associated with the organic sublattice. By selectively substituting hydrogen with deuterium in methylammonium lead iodide, we suppress HFI, as revealed by transient spectroscopic measurements that show a clear extension of the longitudinal spin lifetime under ambient conditions. Furthermore, spin valve devices incorporating deuterated perovskites exhibit enhanced magnetoresistance signals, confirming improved spin transport performance at the device level. This approach reveals that organic cations, long regarded as structurally passive, play an active role in governing spin dynamics, and it offers a practical route to overcome the long-standing limitation of short spin lifetimes in these materials. Our findings emphasize the underestimated role of the nuclear spin environment and underscore the need for a holistic understanding of spin relaxation that includes both inorganic and organic contributions, which is crucial for advancing hybrid perovskite spintronics beyond that based on traditional inorganic and organic semiconductor materials.

Results
Spin valve device based on deuterated perovskite films

The modulation of spin transport dynamics by organic cations in OIHPs remains an open question. They not only influence the structural and electronic properties of hybrid perovskites but also may play a crucial role in spin relaxation mechanisms. Hyperfine interaction (HFI), in particular, represents a key source of spin decoherence, as it couples spin-polarized carriers and nuclear spins, leading to spin relaxation. A potential approach to suppressing HFI is deuteration, where hydrogen in the organic cation is replaced with deuterium30,31. Deuterium has a significantly smaller nuclear magnetic moment (μD = 0.8574μN) than hydrogen (μH = 2.7928μN), where μN is the nuclear magneton, and a different nuclear spin quantum number (I =1, I =1/2)32. As a result, the hyperfine coupling strength is expected to decrease upon deuteration. The ratio of hyperfine coupling constants (A) between hydrogen and deuterium can be estimated as33,34:

𝐴H ⁄ 𝐴D ≈ (𝜇H ⁄ 𝐼H) ⁄ (𝜇D ⁄ 𝐼D) (1)

The hyperfine coupling strength in hydrogen is approximately 6.5 times greater than that in deuterium. This theoretical prediction is further supported by a comparison of their Larmor frequencies, which are directly proportional to the respective gyromagnetic ratios. Under the same magnetic field, hydrogen exhibits a Larmor frequency of 42.58 MHz, while deuterium exhibits 6.54 MHz, again yielding a ratio of approximately 6.5. This quantitative agreement reinforces the hypothesis that deuteration effectively suppresses HFI and may mitigate nuclear spin-induced spin relaxation (Fig.1a). In OIHPs, charge carriers primarily transport through the inorganic Pb–I framework and do not directly traverse the organic components35. However, due to the long-range nature of HFI—which can extend beyond 20 Å36, much greater than the ~3 Å distance between the organic cations (e.g., MA and FA) and the Pb–I lattice37—carriers can still couple with hydrogen nuclei in the organic moieties. This implies that even though the transport path is confined to the inorganic sublattice, spin relaxation may still be significantly affected by the nuclear spins of organic cations. Importantly, such coupling does not require carriers to be statically localized on the organic sublattice. For mobile carriers, the nuclear-spin environment can be viewed as a fluctuating perturbation that is sampled during transport and scattering, which can contribute to spin dephasing/relaxation even when charge transport occurs in the inorganic backbone. In this picture, HFI may contribute as an additional, relatively weak nuclear-spin-related channel that can coexist with SOC-driven mechanisms (e.g., EY/DP), rather than replacing them27,38.

To investigate this effect, we focus on methylammonium lead iodide, a prototypical hybrid perovskite where the organic cation plays a dominant role in modulating HFI. By replacing hydrogen with deuterium in the methylammonium cation, we examine whether the predicted suppression of HFI leads to measurable changes in spin relaxation dynamics. We first synthesized single crystals of CD₃ND₃PbI₃ and confirmed their crystal structure, as shown in Supplementary Fig. 1. UV-visible absorption and photoluminescence spectra of the perovskite thin films (Supplementary Fig. 2) revealed no significant changes upon deuteration, indicating that the substitution does not noticeably alter the electronic structure of the material. This observation is further supported by subsequent X-ray diffraction and X-ray photoelectron spectroscopy data (Supplementary Fig. 3,4). However, the corresponding Fourier-transform infrared (FT-IR) spectra exhibited pronounced differences. Under identical preparation and measurement conditions, the characteristic absorption peaks associated with C–H (2920 cm-1), N–H (3134, 3176, 1577, and 1465 cm-1), and CH₃–NH₃+ (1246 and 906 cm-1) were significantly weakened after deuteration, with partial shifts to lower frequencies leading to the appearance of new absorption peaks at 2600, 1142, and 760 cm-1, which are assigned to CH₃–NH₃+ (Supplementary Fig. 5). These results indicate that the molecular backbone structure and vibrational degrees of freedom remain unchanged after deuteration.

The changes in the FT-IR spectra can be attributed to the suppression of vibrational frequencies and the lowering of molecular vibrational energy induced by deuteration39. This suppression of vibrational motion is further reflected in the photoluminescence behavior of the film: after deuteration, its lifetime increased from 128 ns to 133 ns (Supplementary Fig. 6), most likely as a result of reduced high-frequency vibrations, which in turn lowers the probability of non-radiative transitions. Collectively, these characterizations confirm that while deuteration induces clear vibrational modifications, the perovskite system remains structurally and optically unchanged, thus providing a reliable basis for subsequent investigation of its spin transport behavior.

To evaluate the influence of deuterated perovskites on spin dynamics, we employed a spin valve architecture, as illustrated in Fig. 1b. Co and NiFe were selected as ferromagnetic electrodes due to their high Curie temperatures (>800 °C), enabling stable spin polarization and reliable operation at room temperature. However, the thermal and kinetic energy involved in electrode deposition can damage the spin transport layer, compromising interfacial integrity and spin transport efficiency. To mitigate this, we adopted a low-temperature deposition process to preserve the interface quality40. A 20 nm Co bottom electrode was first deposited on a SiO₂ substrate, serving as the spin injector. Given its high chemical reactivity, Co tends to hybridize with the adjacent perovskite layer, leading to undesirable interfacial effects. To prevent this, a thin aluminum oxide (AlOx) barrier was introduced prior to perovskite deposition, effectively isolating the ferromagnet and maintaining interfacial integrity41. The perovskite layer was then formed by spin-coating and annealing the precursor solution. Using atomic force microscopy, the film roughness was measured to be approximately 1.3 nm, indicating a very smooth surface. This observation was further corroborated by scanning electron microscopy analysis (Supplementary Fig. 7,8). Meanwhile, we found that both the contact angle and surface energy of the film showed no significant changes after deuteration (Supplementary Table 1), which supports the consistent fabrication of the top electrode. Finally, a 12 nm NiFe top electrode was deposited as the spin detector (see Methods and Supplementary Fig. 9 for details).

The spinterface is central to spintronic device performance, governing spin injection, transport, and detection. In spin valves, a well-defined interface minimizes spin relaxation and interfacial scattering, thereby enhancing spin transport. To investigate the interface quality in our device, we conducted cross-sectional transmission electron microscopy (TEM) analysis. The images show sharp, vertically resolved layer boundaries, indicating excellent structural integrity. Notably, no interlayer diffusion or fusion is observed between the NiFe electrode and the OIHP layer (Fig. 1c). Energy-dispersive X-ray spectroscopy (EDS) maps further confirm that each element remains confined within its designated layer, with no evidence of interfacial mixing (Fig. 1d). These findings highlight the effectiveness of our low-temperature deposition strategy in preserving clean interfaces, a prerequisite for achieving room-temperature spin transport in perovskite-based spintronic devices. Furthermore, both ferromagnetic electrodes demonstrated well-defined anisotropic magnetoresistance signals (Supplementary Fig. 10a,b), confirming their magnetic integrity and enabling reliable evaluation of spin transport phenomena in the subsequent device measurements.

We next investigated the magnetic response of the spin valve under a 10 mV bias. The deuterated perovskite thin film exhibited a pronounced magnetocurrent response, with the device current reversibly switching between a high-conductance state under parallel magnetization and a low-conductance state under antiparallel alignment. Upon rapid modulation of the magnetic field, the deuterated spin valve demonstrated fast and stable magnetocurrent switching over 6,454 cycles. The standard deviations (σ) of the current in the parallel and antiparallel states were approximately 0.0048 and 0.0059 of their respective mean values, with 98.6% and 98.2% of the output data points falling within the ±3σ range (Fig. 1e). According to the definition of magnetocurrent:

MC = (IP - IAP) ⁄ IAP × 100% (2)

where IP and IAP represent the currents under parallel and antiparallel magnetization, respectively5,42, the MC ratio of the deuterated perovskite device was determined to be 17.5% at room temperature (Fig. 1f). Such a substantial magnetocurrent signal under ambient conditions is rarely observed in perovskite-based systems. Based on devices with varying film thicknesses, the spin diffusion length of the deuterated perovskite was extracted to be 78 nm at room temperature (Supplementary Fig. 10c). In contrast, the spin valve using non-deuterated perovskite thin film exhibited a negligibly smaller MC < 1% (Fig. 1g), which was insufficient to support reliable cycling or thickness-dependent measurements under the same conditions.

The long-term stability of spintronic performance is critical for practical applications. We evaluated the room-temperature durability of deuterated and non-deuterated perovskite spin valves by monitoring their MC signals over extended storage times. As shown in Supplementary Fig. 10d, the MC signal of the non-deuterated device rapidly decayed, with a reduction of ~50% within 100 days and nearly complete loss (~1%) after 400 days. Remarkably, the deuterated perovskite device exhibited exceptional stability, retaining over 93% of its MC value after 100 days and approximately 75% after 400 days. This improvement is attributed to the suppression of hydrogen-related degradation pathways, as the heavier deuterium atoms reduce the vibrational frequency of hydrogen bonds, thereby slowing hydrogen migration and associated decomposition reactions. These results reveal the key role of deuteration in enhancing spin transport and stability in OIHPs, establishing a basis for spintronic device integration. Their robust room-temperature performance suggests OIHPs may serve as versatile platforms bridging photovoltaic, spintronic and quantum functionalities.

Room-temperature spin lifetime

To explore the role of organic cations in spin relaxation, we investigate how deuteration of the organic ligand influences spin dynamics in hybrid perovskites. Using circularly polarized transient absorption (TA) spectroscopy, we track the evolution of spin-polarized photogenerated carriers and reveal the impact of deuteration on longitudinal spin relaxation time43–45. The experiments employ a pump-probe configuration, where a left-circularly polarized pump pulse (σ⁻) selectively excites the sample, generating spin-polarized carriers. The evolution of these spin-polarized carriers is monitored via a left-circularly polarized probe pulse (σ⁻), tracking the photobleaching (PB) signal, as shown in the inset of Fig. 2a and Supplementary Fig. 11. A characteristic fingerprint of spin depolarization is observed as the decay of the σ⁻ PB signal is accompanied by the simultaneous emergence of a σ⁺ PB signal, indicating spin flipping driven by relaxation mechanisms.

We identify the primary PB feature within the 730–780 nm spectral range, which reflects state filling of spin-polarized carriers at early times following excitation (Fig. 2a). Notably, deuteration of the organic cation does not shift the PB peak positions, confirming that the fundamental band structure remains unchanged. However, the spin dynamics exhibit a pronounced change: as shown in Fig. 2b, the crossover between the left- and right-circularly polarized TA signals is significantly delayed in deuterated perovskites compared to their non-deuterated counterparts, indicating a prolonged longitudinal spin relaxation process.

To quantitatively extract the spin relaxation dynamics shown in Fig. 2c, we define the spin-polarized transient absorption signal as the difference between the bleach kinetics measured under opposite pump helicities while keeping the probe helicity fixed:

ΔAspin(t) = ΔAσ−pump,σ−probe(t) - ΔAσ+pump,σ−probe(t) (3)

The resulting spin polarization decay was fitted using a single-exponential function46–48,

ΔAspin(t) = A0 exp(-t ⁄ τspin) (4)

where A0 denotes the initial spin-polarized bleach amplitude and τspin represents the longitudinal spin lifetime. The extracted longitudinal spin lifetime of CH₃NH₃PbI₃ is 4.7 ps, whereas CD₃ND₃PbI₃ exhibits an extended lifetime of 12.4 ps, corresponding to a 2.6-fold enhancement. Notably, a measurable isotope dependence does not require the hyperfine channel to dominate over SOC-driven processes. Instead, in a multi-channel picture the total spin-decay rate can be written as 1/τs = 1/τSOC + 1/τHFI; therefore, selectively weakening the nuclear-spin-related term can still produce a increase in τs even when SOC-driven EY/DP channels remain operative19,38. This pronounced isotope dependence supports that the organic-cation nuclear-spin environment contributes measurably to spin decay in OIHPs. Therefore, deuteration provides a practical and selective strategy to tune this nuclear-spin-related channel and enhance room-temperature spin transport.

Carrier mobility

To investigate the impact of deuterated organic cations on carrier transport properties, we employed transient reflectivity microscopy to probe the carrier dynamics in the material. This technique enables high spatial and temporal resolution optical detection of photoexcited carrier density and diffusion behaviour by monitoring changes in reflectivity (ΔR/R) induced by excited states, providing a reliable approach to characterize charge transport49. The corresponding experimental setup is illustrated in Supplementary Fig. 12. By systematically varying the delay between pump and probe pulses, we acquired two-dimensional reflectivity maps at different time delays for CD₃ND₃PbI₃, as shown in Fig. 3a. The corresponding data for CH₃NH₃PbI₃ are provided in Supplementary Fig. 13. To visualize the spatial characteristics of carrier diffusion, the reflectivity distribution at 10 ps was fitted with a two-dimensional Gaussian function and rendered as a three-dimensional pseudocolour map (Fig. 3b). Subsequently, one-dimensional spatial profiles of the normalized ΔR/R signal were extracted from the central region of each time-delayed map to construct Fig. 3c. These profiles were then fitted with Gaussian functions, and the resulting variance, σ², was used as a measure of the carrier distribution width.

The time-dependent evolution of 𝜎2 with varying time delay is presented in Fig. 3d, where a linear increase in variance with time is observed, characteristic of diffusive transport. The diffusion coefficient D was obtained by fitting the data to the relation50:

𝜎2(t) = 𝜎2(0) + 2Dt (5)

Here, 𝜎2(t) represents the carrier distribution variance at time t, while 𝜎2(0) is the variance at t=0. The slope of the fit provides the diffusion coefficient D, and using the Einstein relation51:

D = μ(kBT ⁄ e) (6)

where kB is the Boltzmann constant, T is the absolute temperature, and e is the elementary charge, the carrier mobility μ was calculated. From the linear fit in Fig. 3d, we obtain mobilities of 54.9 ± 1.1 cm² V⁻¹ s⁻¹ for CH₃NH₃PbI₃ and 51.3 ± 1.6 cm² V⁻¹ s⁻¹ for CD₃ND₃PbI₃ (mean ± s.d.; Supplementary Fig. 14). Mobilities thus remain on the same order (~50 cm² V⁻¹ s⁻¹) in both films, indicating that deuteration has a very limited impact on charge transport. The small, reproducible reduction upon deuteration may reflect subtle isotope-dependent changes in carrier–lattice coupling and dynamic disorder. Furthermore, the spin diffusion length can be estimated using the extracted longitudinal spin lifetime and carrier diffusion coefficient as16:

λs = √3Dτs (7)

Using this relation, we obtain a spin diffusion length of approximately 70 nm for CD₃ND₃PbI₃, which is in good agreement with the value independently derived from thickness-dependent device measurements. The increased spin diffusion length in the deuterated device allows a higher fraction of injected spins to survive across the perovskite spacer, reducing bulk spin loss and enabling efficient detection, consistent with the enhanced room-temperature MC. More importantly, these observations further substantiate that in hybrid perovskites, carriers predominantly transport through the inorganic framework, with minimal influence from the organic cations. In contrast, our previous spin transport and spin lifetime experiments demonstrated that deuteration can effectively modulate spin polarization. This divergence suggests that even though spin-polarized carriers do not directly traverse the organic cations, their spin dynamics can still be influenced by HFI induced by hydrogen.

Room-temperature spin photovoltaic effect

OIHPs have a high absorption coefficient, allowing even ultra-thin layers to effectively absorb photons and generate carriers. Moreover, their excellent charge separation and transport properties facilitate the rapid migration of carriers52,53. An interplay between electrically injected spin-polarized carriers and photogenerated non-polarized carriers is central to unlocking room-temperature spin functionalities in perovskite materials (Fig. 4a). Under illumination with 4 mW cm⁻² white light and in the absence of an external bias, the perovskite layer absorbs photons and generates non–spin-polarized carriers. These carriers drift toward the ferromagnetic electrodes under the built-in potential, giving rise to a photocurrent (Supplementary Fig. 15a). Under these conditions, as shown in Supplementary Fig. 15b, the device produces a measurable photocurrent. When an external bias is applied under illumination, the spin-polarized current injected from the ferromagnetic electrode flows in the opposite direction to the non–spin-polarized photocurrent, leading to mutual cancellation (Supplementary Fig. 15c). Because the spin valve employs ferromagnetic electrodes, sweeping the magnetic field switches the device between parallel and antiparallel configurations due to the different coercive fields of the electrodes. In the parallel configuration, where the spin orientations of the two electrodes are aligned, the bias-injected carriers can reach the Co electrode and recombine efficiently, resulting in a relatively low photogenerated voltage VOC,P. From the corresponding I–V curve, we extracted an open-circuit voltage VOC,P of 18.4 mV and a short-circuit current ISC of 2.4 nA (Supplementary Fig. 15d). In contrast, in the antiparallel configuration, the spin current encounters electrodes with opposite spin orientations, leading to enhanced scattering (Supplementary Fig. 15e). As a result, a larger external bias is required in the I–V measurement to compensate for the scattering-induced changes (Supplementary Fig. 15f). Consequently, a higher VOC,AP is needed to maintain the zero-current condition, yielding VOC,AP > VOC,P. Due to the limited transparency of the top NiFe electrode, both VOC and ISC are lower than those typically observed in conventional photovoltaic devices.

As shown in Fig. 4b, under a fixed external bias of 10 mV, the photocurrent generated by the photovoltaic effect flows in the opposite direction to the current injected by the external bias. As the light intensity increases, the total device current crosses zero and shifts toward the negative direction. Furthermore, under specific light intensities, the spin valve exhibits magnetocurrent switching between low and high states as the external magnetic field is swept across zero (Supplementary Fig. 16). By maintaining a constant illumination intensity, the current versus magnetic field (I–B) characteristics can be tuned by adjusting the external bias (Fig. 4c). As the applied bias is gradually increased from 0 mV to 40 mV, the device current transitions from negative to positive, while ΔIout between the parallel and antiparallel states steadily increases. The impact of light intensity and applied bias on ΔIout is summarized in Fig. 4d. This result unambiguously demonstrates that the applied bias governs the number of spin-polarized carriers injected from the ferromagnetic electrode, which fundamentally determines the variation in ΔIout. Although photogenerated non-spin-polarized carriers do not directly affect spin-polarized transport, they effectively modulate the device current and consequently influence the MC magnitude. Notably, when the device current is tuned near zero, the MC value approaches infinity (Fig. 4e). Moreover, under specific light intensity and applied bias conditions, the output current of the device can be tuned close to zero. In this regime, the MC signal output during the external magnetic field sweep originates purely from the spin-polarized current (Fig. 4f). Under these conditions, the background operating current of the device is entirely suppressed, presenting a promising approach for the realization of low-power spintronic devices operating at room temperature.

Results and Discussion

In summary, we find that HFI represents a non-negligible and previously underappreciated factor in spin relaxation processes within OIHPs. By replacing hydrogen with deuterium in CH₃NH₃PbI₃, we suppress HFI and extend the spin lifetime from 4.7 ps to 12.4 ps while maintaining high carrier mobility of 51.1 cm²/V·s, resulting in a robust room-temperature magnetocurrent of 17.5%. Furthermore, the observed room-temperature spin photovoltaic effects reveal a strong interplay between optical excitation and spin dynamics in hybrid perovskites. The findings reveal that organic cations, long overlooked in studies of spin dynamics, play a significant role in hybrid perovskites. Their measurable impact on spin transport offers new insights into spin relaxation mechanisms and provides a foundation for tuning spintronic properties in perovskite-based devices.

Methods
Preparation of CD₃ND₃PbI₃

All starting materials were purchased from Energy Chemical. CD₃ND₂ was obtained by dissolving anhydrous methylamine gas in D₂O. Lead(II) acetate trihydrate was dissolved in D₂O three times to promote H/D exchange and then dried under vacuum. Deuterated hydroiodic acid (DI, 57 wt% in water) was synthesized by reacting 50 wt% hypophosphorous acid–d₃ (in D₂O) with potassium iodide (KI) at 170 °C. The resulting DI vapor was condensed and collected.

For crystal growth54, 1 M solutions of PbI₂ and CD₃ND₃I were prepared separately in γ-butyrolactone (GBL) and heated to 60 °C. The solutions were filtered using a 0.2 μm PTFE syringe filter, and 2 mL of the filtered solution was transferred to a vial and placed in a 110 °C oil bath. Crystals began to appear after ~20 min. The crystals were collected, washed three times with deuterated diethyl ether, and vacuum-dried at room temperature. The synthesized CD₃ND₃PbI₃ was characterized by ¹³C nuclear magnetic resonance spectroscopy, performed on a Bruker Avance 600 MHz NMR spectrometer at 25 °C using deuterated DMSO as the solvent. The methyl carbon peak of CD₃ND₃PbI₃ appears around 23.8 ppm. The multiple splittings of this peak indicate the successful synthesis of the deuterated perovskite CD₃ND₃PbI₃ (Supplementary Fig. 17). The unit cell parameters obtained from single-crystal analysis are listed in Supplementary Table 2.

Preparation of Perovskite Films

The precursor solution was prepared by dissolving methylammonium iodide (MAI) and lead iodide (PbI₂) in a 1:1 molar ratio. The mixture was stirred in N,N-dimethylformamide at 60 °C for 12 hours. The resulting solution was then spin-coated onto glass substrates and subsequently annealed at 120 °C for 25 minutes under a nitrogen atmosphere.

Device fabrication and measurements

Prior to fabrication, the substrates were sequentially cleaned in deionized water, isopropanol, and acetone using ultrasonic treatment for a total duration of one hour. After cleaning, the substrates were dried with a nitrogen flow. Cobalt (Co) bottom electrodes were deposited by high-vacuum electron beam evaporation through a shadow mask at a deposition rate of approximately 1 Å/s. Subsequently, a thin aluminum layer (~1.7 nm) was thermally evaporated at 0.3 Å/s, followed by immediate air plasma oxidation to form a tunneling AlOx layer. Perovskite precursor solutions were spin-coated onto the substrates inside a nitrogen-filled glovebox to achieve films of varying thicknesses. On top of the perovskite layer, a 12 nm NiFe top electrode was deposited using a low-temperature process to minimize damage to the underlying organic layer. The deposition was performed at a rate of 0.7 Å/s with a shadow mask to define the device area, which was approximately 0.2 mm². The thickness of the intermediate layer was determined by spectroscopic ellipsometry (SE-VE-L, Wuhan Eoptics Technology Co., Ltd).

Magnetocurrent measurements were conducted using a vacuum magnetic probe station (CRX-EM-HF, Lake Shore Cryotronics Co., Ltd.) employing a standard four-probe configuration. The spin diffusion length was extracted using the modified Jullière model, described by the following expression:

MC = (IP - IAP) ⁄ IAP = 2P1P2 e-(d-d0)⁄λs ⁄ (1 + P1P2 e-(d-d0)⁄λs) (8)

where d represents the thickness of the organic spacer layer between the ferromagnetic electrodes, and d₀ accounts for the thickness of the ill-defined interfacial region. P₁ and P₂ correspond to the spin polarization at the injection and detection interfaces, respectively.

Cross-sectional high-resolution transmission electron microscopy (HRTEM) samples were prepared using a focused ion beam (FIB) system (FEI Strata DB235). A 100 nm thick Al protective layer was deposited on top of the devices prior to FIB milling. High-resolution TEM images were acquired using an FEI G2 F30 microscope operated at an accelerating voltage of 300 kV.

Transient Absorption Spectroscopy with Circular Polarization

The transient absorption measurement is based on the femtosecond laser (ORPHEUS-HP, Light Conversion) and the transient absorption spectrometer (HARPIA-TA, Light Conversion). An ultrafast pump laser beam is converted into right or left circularly polarized light by a Berek compensator. A white light probe beam is converted into left circularly polarized light using a linear polarizer and a quarter wave plate.

Transient Reflection Microscopy

Ultrafast transient reflection microscopy was performed using an experimental setup previously constructed by our collaborators. In this setup, a portion of the 800 nm femtosecond laser output was frequency-doubled to 400 nm via a β-Barium borate (BBO) crystal to serve as the pump beam. The probe beam was generated by an optical parametric amplifier (OPA), providing tunable output for selective excitation and detection. The two beams were spatially overlapped on the sample through a custom-built microscope platform, enabling diffraction-limited spatial resolution. Temporal delay between pump and probe pulses was introduced using a motorized delay stage, allowing for time-resolved mapping of the transient optical response.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This manuscript reports that efficient room-temperature spin transport in organic-inorganic hybrid perovskite can be achieved through isotope engineering, specifically by substituting hydrogen with deuterium in methylammonium lead iodide to effectively suppress the previously overlooked hyperfine interactions of the organic sublattice. By studying the longitudinal spin lifetime, the magnetocurrent of spin-valve devices, and the spin photovoltaic effect, the authors provided some fundamental understanding of spin relaxation in hybrid materials and established isotope engineering as a powerful strategy to access robust, room-temperature spin functionality. However, the manuscript would benefit from clarifying several uncertain points to support its hypothesized statements.\n1. The authors note that although charge carriers mainly propagate within the inorganic Pb–I framework, the hyperfine interaction possesses a long-range character extending beyond 20 Å, which is significantly greater than the ~3 Å separation between the organic cations and the inorganic lattice. While this feature could, in principle, explain how charge carriers couple to the nuclear spins of the organic cations, the manuscript does not clearly elaborate or model how such a long-range HFI dynamically interacts with the rapidly moving spin-polarized carriers in the inorganic backbone, nor does it discuss its relative contribution to established spin-relaxation mechanisms such as the Elliott–Yafet and D’yakonov–Perel’ processes. Moreover, although the authors provide theoretical calculations indicating that deuteration weakens the HFI coupling strength by approximately 6.5 fold, the manuscript does not quantitatively relate this reduction to the observed 2.6 fold increase in spin lifetime. A more detailed quantitative correlation or mechanistic analysis would strengthen the argument and improve the overall clarity of the discussion.\n2. The manuscript reports carrier mobility values measured by transient reflection microscopy: 54.5 cm² V⁻¹ s⁻¹ for the non-deuterated material and 51.1 cm² V⁻¹ s⁻¹ for the deuterated counterpart. Although FT-IR and photoluminescence lifetime measurements confirm that deuteration suppresses vibrational frequencies and lowers molecular vibrational energies, the manuscript does not clearly establish how this specific vibrational softening quantitatively or mechanistically translates into enhanced scattering during carrier transport, thereby causing the observed minor decrease in mobility. A more explicit discussion connecting the vibrational changes to charge-transport dynamics would help substantiate this interpretation.\n3. The manuscript reports the observation of a room-temperature spin photovoltaic effect and highlights that, by carefully tuning the light intensity and applied bias, the total device current can be adjusted to approaching zero. When the total current approaches zero, the magnetocurrent value tends toward infinity. The manuscript presents this as a potential route toward realizing ultra-low-power spintronic devices; however, it does not further discuss the operational precision required to maintain such an exact zero-current balance, nor the stability and reproducibility of this condition for practical applications.", "reviewer_2": "This manuscript presents the suppression of hyperfine interaction in hybrid perovskites through isotope engineering (H → D substitution), leading to enhanced spin lifetime, improved room-temperature spin transport, and the demonstration of a spin photovoltaic effect (S-PV). The topic is timely and scientifically meaningful; however, several key aspects of the analysis remain largely qualitative, and the physical interpretations rely on descriptive explanations rather than quantitative or model-supported arguments. For publication in Nature Communications, the manuscript requires substantial reinforcement in the following areas.\n1. Although the authors extract the longitudinal spin lifetime from transient absorption measurements, the manuscript does not describe how the fitting was performed or what kinetic model was applied. Because spin-lifetime values depend strongly on the functional form used for fitting, omitting this information significantly limits reproducibility and undermines the credibility of the extracted parameters.\nMoreover, while the authors estimate the spin diffusion length using the measured lifetime and diffusion parameters, the manuscript does not provide a physical, device-level interpretation of what this means for the present spin-valve structure. Specifically, the manuscript should address how much the increased spin lifetime actually improves spin survival across the perovskite spacer thickness used in the device, and what quantitative advantage deuteration provides under the real operating geometry. Without such analysis, the reader cannot assess the actual impact of isotope substitution on the device performance. So, the authors should improve insufficient description of the spin-lifetime extraction method and incomplete discussion of spin diffusion length.\n2. Figure 3 shows that the difference in mobility between the protonated and deuterated samples is extremely small - approximately 6%, well within typical sample-to-sample or measurement variation. Nonetheless, the authors interpret this minor change as evidence for increased scattering due to vibrational suppression. This interpretation is not supported by the magnitude of the observed variation, which is too small to draw conclusions about altered scattering mechanisms.\nA more reasonable interpretation is that deuteration has minimal influence on carrier mobility. The manuscript should avoid overstating the physical significance of such a small variation unless statistical evidence (error bars, repeated measurements) is presented to justify it.\n3. The spin photovoltaic effect (S-PV) is one of the central claims of this manuscript. However, the explanation provided in Figure 4a is conceptual only, and the manuscript does not present any quantitative model that can logically connect the schematic to the experimental results in Figures 4b, 4c, or 4f.\nIn particular, the following questions remain unanswered:\n- Quantitative analysis about the total current reverse sign as illumination increases?\n- Quantitative analysis about that the parallel and antiparallel configurations yield different photovoltages\n- Under what specific bias–illumination conditions can the authors tune the output current exactly to zero?\n- How much carrier reflection or suppression occurs in the antiparallel configuration, and what determines this magnitude?\nAll of these effects are described qualitatively but not supported by a quantitative charge-transport or spin-dependent recombination model. For a claim as central as a room-temperature S-PV effect, at least a minimal theoretical framework is required to justify the physical interpretation and distinguish this work from prior studies.\n4. The authors argue that the increase in spin lifetime due to deuteration leads to an enhancement in photovoltage and S-PV contrast. However, photovoltaic voltage is influenced by multiple factors - recombination dynamics, interfacial energetics, spin-selective reflection, and charge-transport asymmetry - and the manuscript does not demonstrate how the longer spin lifetime affects these parameters.\nIn its current form, the manuscript presents the argument in a purely qualitative manner, without explaining the mechanism by which enhanced spin lifetime translates into measurable shifts in photovoltage between the parallel and antiparallel configurations. To claim a fundamentally new S-PV mechanism enabled by isotope engineering, the authors must provide a more rigorous, model-based discussion linking the observed spin dynamics to the photovoltaic response.\nThis work offers an intriguing direction by combining isotope engineering with perovskite spintronics, and the experimental results are potentially impactful. However, the central claims - particularly those related to spin lifetime extraction, spin diffusion length relevance, spin photovoltaic operation, and the mechanistic role of deuteration - are supported primarily by qualitative descriptions rather than quantitative or model-based analysis.\nTo meet the standards of Nature Communications, the manuscript requires substantial strengthening of its physical arguments and quantitative justification. A more rigorous analytical framework is essential for clearly establishing the novelty and validity of the reported phenomena.", "reviewer_3": "In this manuscript, the authors present compelling and somewhat unexpected results regarding spin transport in hybrid organic–inorganic perovskites (OIHPs). They synthesize both single crystals and thin films of CH3NH3PbI3 and its deuterated analogue (CD3ND3PbI3), and demonstrate that spin transport is dramatically enhanced in the deuterated compound. The structural characterization is thorough and convincingly shows that the two materials are nearly identical from the perspective of crystallography and electronic structure, while their vibrational spectra differ substantially. In addition, the charge-carrier mobility, determined via transient reflectivity microscopy, is comparable in both systems, suggesting similar charge-transport mechanisms.\nThe authors therefore conclude that spin transport is primarily influenced by hyperfine interactions (HFI) originating from hydrogen nuclei in the organic cation, rather than by differences in structure, defects, or charge mobility. The demonstration of a room-temperature spin photovoltaic effect in deuterated perovskite spin valves adds multifunctionality and further strengthens the significance of the work.\nOverall, the manuscript is interesting and the results will likely attract the attention of the Nature Communications readership. However, I have several points that require clarification before the paper can be considered for publication:\n1. As the authors themselves note, HFI from hydrogen in OIHPs is typically considered negligible compared to the strong spin–orbit coupling of the Pb–I sublattice, which is thought to dominate spin dephasing. Here, the experimental data clearly show that suppressing HFI via deuteration has a dramatic impact on spin lifetime and spin transport. I think the authors should elaborate—at least qualitatively—on why hydrogen HFI is not overshadowed by SOC-induced mechanisms in this system. A conceptual or semi-quantitative discussion would be helpful, even if tentative.\n2. In Fig. 1f,g, the magnetocurrent is presented, but no information is given about the device resistance or RA product. A comment on the absolute device resistance would be important—does deuteration affect the resistance or RA product? Similarly, in Fig. 10c (Supplementary), MC is shown as a function of OIHP thickness. It would be important to show or at least comment on how the resistance evolves with thickness. One would expect a significant increase. Is it the case?\n3. The authors estimate the spin diffusion length for the deuterated compound based on tau and D. Can a similar estimate be provided for CH3NH3PbI3?\n4. How is the thickness controlled or monitored across samples? Via spin-coating parameters? Profilometry? Ellipsometry? More detail would help assess reproducibility of the thickness-dependent measurements.\n5. It is unclear whether the measurements in Fig. 2 and Fig. 3 were performed on thin films or single crystals. Since spin dynamics and carrier mobility can differ significantly depending on morphology, the authors should state explicitly which type of sample was used in each measurement.\nIn summary, I find this to be an interesting piece of work with strong potential impact. Addressing the points above would significantly strengthen the manuscript and improve its clarity."}, "author_response": "Point-by-Point Response to Reviewer’s Comments\nReviewer #1 (Remarks to the Author):\nThis manuscript reports that efficient room-temperature spin transport in organic-inorganic hybrid\nperovskite can be achieved through isotope engineering, specifically by substituting hydrogen\nwith deuterium in methylammonium lead iodide to effectively suppress the previously overlooked\nhyperfine interactions of the organic sublattice. By studying the longitudinal spin lifetime, the\nmagnetocurrent of spin-valve devices, and the spin photovoltaic effect, the authors provided some\nfundamental understanding of spin relaxation in hybrid materials and established isotope\nengineering as a powerful strategy to access robust, room-temperature spin functionality. However,\nthe manuscript would benefit from clarifying several uncertain points to support its hypothesized\nstatements.\nAnswer:\nThank you very much for reviewer’s positive comments. We carefully read your suggestions and\ntry our best to revise the paper. Now, we hope you will be satisfied with our revised manuscript.\nQuestion 1-1\nThe authors note that although charge carriers mainly propagate within the inorganic Pb–I\nframework, the hyperfine interaction possesses a long-range character extending beyond 20 Å,\nwhich is significantly greater than the ~3 Å separation between the organic cations and the\ninorganic lattice. While this feature could, in principle, explain how charge carriers couple to the\nnuclear spins of the organic cations, the manuscript does not clearly elaborate or model how such\na long-range HFI dynamically interacts with the rapidly moving spin-polarized carriers in the\ninorganic backbone, nor does it discuss its relative contribution to established spin-relaxation\nmechanisms such as the Elliott–Yafet and D’yakonov–Perel’ processes. Moreover, although\nthe authors provide theoretical calculations indicating that deuteration weakens the HFI coupling\nstrength by approximately 6.5 fold, the manuscript does not quantitatively relate this reduction to\nthe observed 2.6 fold increase in spin lifetime. A more detailed quantitative correlation or\nmechanistic analysis would strengthen the argument and improve the overall clarity of the\ndiscussion.\nAnswer:\nWe thank the reviewer for this thoughtful comment. Spin relaxation in perovskites is typically\ndiscussed within an SOC-dominated framework, where Elliott–Yafet (EY) and D’yakonov–\nPerel’ (DP) mechanisms are expected to provide the primary intrinsic relaxation pathways under\nidealized conditions (Nat. Commun. 15, 188 (2024)).\nImportantly, organic–inorganic hybrid perovskites differ from fully inorganic perovskites in\nmaterials aspects that are directly relevant to spin dynamics. Hybrid perovskites possess a soft\nlattice with pronounced dynamic disorder and strong carrier–lattice coupling, which is well\ndocumented for lead-halide perovskites (Chem 4, 2826–2843 (2018)). In addition, the organic\nsublattice introduces a dense nuclear-spin environment (abundant 1H), a feature absent (or greatly\nreduced) in fully inorganic analogues, and hyperfine-related effects on carrier-spin dynamics have\nbeen explicitly identified in lead-halide perovskites (Adv. Mater. 34, 2105263 (2022)).\nWithin semiconductor spin-dynamics theory, hyperfine interaction (HFI) is commonly formulated\nvia an effective hyperfine (Overhauser) field acting on the carrier spin, where temporal\nfluctuations of this nuclear-spin field provide a standard route to spin dephasing/relaxation (Phys.\nRep. 493, 61–236 (2010)). In lead-halide perovskite nanocrystals, nuclear-spin (hyperfine)\nfields\nhave also been experimentally shown to measurably influence spin polarization decay and to\ninduce spin precession, demonstrating that nuclear-spin effects need not be fully “averaged out”\nin realistic perovskite spin environments (Phys. Rev. B 110, 235301 (2024)). Accordingly, we\nposition HFI as an additional nuclear-spin-related channel that can coexist with SOC-driven\nEY/DP mechanisms in hybrid perovskites, rather than replacing them. We have revised the\nmanuscript accordingly to clarify this physical picture (Lines 100–106).\nTherefore, the spin relaxation is determined by the contributions from SOC and HFI. To make this\ncoexistence transparent at a semi-quantitative level, we describe the spin-polarization decay as\n𝑆(𝑡)=𝑆 𝑒−𝑡/𝜏𝑠, where Γ≡1/𝜏 is the spin-decay rate. If two independent channels contribute to\n0 𝑠\nan approximately exponential decay, their effects add at the level of rates, giving Γ =Γ +\ntot SOC\nΓ , i.e.\nHFI\n1 1 1\n= + .\n𝜏 𝜏 𝜏\n𝑠 SOC HFI\nBy taking the changes in HFI strength (6.5 fold) and spin lifetime (2.6 fold), we can obtain that the\ncontributions of HFI and SOC are roughly 2.7:1 to the spin relaxation in CH₃NH₃PbI₃, while it\nreduces to 0.4:1 in CD₃ND₃PbI₃. The contribution of HFI is related not only to the number of\nprotons but also to the extent of carrier trapping/localization. The factor of 6.5 refers to the\nreduction in hyperfine coupling strength, not the increase in spin lifetime. The spin lifetime is\ninfluenced not only by the hyperfine interaction but also by SOC-related mechanisms. Therefore,\nthe two factors are not expected to scale directly with each other.\nQuestion 1-2\nThe manuscript reports carrier mobility values measured by transient reflection microscopy: 54.5\ncm² V⁻¹ s⁻¹ for the non-deuterated material and 51.1 cm² V⁻¹ s⁻¹ for the deuterated counterpart.\nAlthough FT-IR and photoluminescence lifetime measurements confirm that deuteration\nsuppresses vibrational frequencies and lowers molecular vibrational energies, the manuscript\ndoes not clearly establish how this specific vibrational softening quantitatively or mechanistically\ntranslates into enhanced scattering during carrier transport, thereby causing the observed minor\ndecrease in mobility. A more explicit discussion connecting the vibrational changes to charge-\ntransport dynamics would help substantiate this interpretation.\nAnswer:\nThanks very much for reviewer’s comments. To evaluate this effect, we have added additional\nmeasurements and now report the statistics (mean ± s.d; Supplementary Fig. 14): the mobility is\n54.9 ± 1.1 cm² V⁻¹ s⁻¹ for CH₃NH₃PbI₃ and 51.3 ± 1.6 cm² V⁻¹ s⁻¹ for CD₃ND₃PbI₃. These data\nindicate that the charge mobilities remain on the same order (~50 cm² V⁻¹ s⁻¹) for both films,\nand\nthat deuteration has a very limited impact on charge transport.\nDeuteration lowers the vibrational frequencies of the organic cation (as confirmed by our FT-IR\nresults) and may also modify the coupled lattice dynamics in hybrid perovskites. For example,\ninelastic neutron scattering studies have shown that deuteration in CH₃NH₃PbI₃ can lead to\nsoftening of longitudinal acoustic phonons, arising from coupling between lattice phonons and\nmethylammonium librational modes (Sci. Adv. 6, eaaz1842 (2020)). Such isotope-induced\nchanges in the phonon spectrum and molecular–lattice dynamics could, in principle, influence\ncarrier scattering and the effective mobility; related observations have also been discussed in\norganic semiconductors (Adv. Electron. Mater. 3, 1700018 (2017)). However, given the modest\nmagnitude observed here, we describe the mobility change as a small effect that may be related to\nsubtle isotope-induced changes in lattice/molecular dynamics, rather than attributing it to a\nspecific scattering mechanism. To avoid potential ambiguity, we have revised the corresponding\ndescription in the main text (Lines 305–311) and removed the overly strong mechanistic wording,\nemphasizing instead that deuteration only weakly affects charge transport.\nQuestion 1-3\nThe manuscript reports the observation of a room-temperature spin photovoltaic effect and\nhighlights that, by carefully tuning the light intensity and applied bias, the total device current can\nbe adjusted to approaching zero. When the total current approaches zero, the magnetocurrent value\ntends toward infinity. The manuscript presents this as a potential route toward realizing ultra-low-\npower spintronic devices; however, it does not further discuss the operational precision required to\nmaintain such an exact zero-current balance, nor the stability and reproducibility of this condition\nfor practical applications.\nAnswer:\nWe thank the reviewer for raising the important concern regarding the operational precision\nrequired to achieve and maintain the near-zero current condition. In our spin photovoltaic devices,\nthe total current is governed by two independently and continuously tunable parameters: the\nillumination intensity and the applied bias. In practice, both parameters are precisely controlled\nvia software, which allows real-time monitoring of the device current. By tracking the current\nevolution and iteratively adjusting the bias voltage and light intensity, the device can be\nreproducibly tuned into a near-zero current regime. Importantly, an exact zero-current condition is\nnot strictly required; small deviations still yield strongly enhanced magnetocurrent values, making\nthe effect experimentally accessible rather than relying on an idealized singular point.\nRegarding stability and reproducibility, we emphasize that the key factor for the spin photovoltaic\neffect is the stability of spin polarization rather than the photovoltaic response itself. The latter is\nan intrinsic property of the perovskite material and remains stable as long as the material does not\nundergo degradation. In our manuscript, the spin stability has already been systematically\nevaluated through long-term spin-valve measurements. As shown in Supplementary Fig. 10d,\ndeuterated perovskite spin valves retain over 93% of their magnetocurrent after 100 days and\napproximately 75% after 400 days at room temperature, demonstrating excellent long-term spin\nstability. This robustness ensures that the spin photovoltaic response, including the near-zero\ncurrent operating regime, is stable. In addition, the device shows highly reproducible spin-valve\nswitching under rapid field modulation over 6,454 cycles, with small fluctuations in both the\nparallel and antiparallel current levels (Fig. 1e), supporting robust short-term operational\nreproducibility. These results confirm that the proposed electro-optical tuning strategy is\ncompatible with practical device operation and long-term storage.\nReviewer #2 (Remarks to the Author):\nThis manuscript presents the suppression of hyperfine interaction in hybrid perovskites through\nisotope engineering (H → D substitution), leading to enhanced spin lifetime, improved room-\ntemperature spin transport, and the demonstration of a spin photovoltaic effect (S-PV). The topic\nis timely and scientifically meaningful; however, several key aspects of the analysis remain largely\nqualitative, and the physical interpretations rely on descriptive explanations rather than\nquantitative or model-supported arguments. For publication in Nature Communications, the\nmanuscript requires substantial reinforcement in the following areas.\nWe appreciate the reviewer for the overall positive evaluation and his/her time and efforts in\nexamining our work. In the following, we have provided detailed responses to the reviewer’s\ncomments, and the main text and Supplementary Information have been revised accordingly.\nQuestion 2-1\nAlthough the authors extract the longitudinal spin lifetime from transient absorption\nmeasurements, the manuscript does not describe how the fitting was performed or what kinetic\nmodel was applied. Because spin-lifetime values depend strongly on the functional form used for\nfitting, omitting this information significantly limits reproducibility and undermines the credibility\nof the extracted parameters\nMoreover, while the authors estimate the spin diffusion length using the measured lifetime and\ndiffusion parameters, the manuscript does not provide a physical, device-level interpretation of\nwhat this means for the present spin-valve structure. Specifically, the manuscript should address\nhow much the increased spin lifetime actually improves spin survival across the perovskite spacer\nthickness used in the device, and what quantitative advantage deuteration provides under the real\noperating geometry. Without such analysis, the reader cannot assess the actual impact of isotope\nsubstitution on the device performance. So, the authors should improve insufficient description of\nthe spin-lifetime extraction method and incomplete discussion of spin diffusion length.\nAnswer:\nWe thank the reviewer for raising these important points regarding the extraction and\ninterpretation of the longitudinal spin lifetime. We agree that a clear description of the fitting\nprocedure and a device-relevant discussion of the spin diffusion length are essential for\nreproducibility and for assessing the physical significance of the results. In the revised manuscript,\nwe have addressed these concerns as detailed below.\nFirst, we have substantially clarified the procedure used to extract the longitudinal spin lifetime\nfrom the circularly polarized transient absorption measurements. In our analysis, we adopt a\nsingle-exponential decay form based on a rate-equation description of spin polarization (Sci. Adv.\n6, eabb7132 (2020); Nat. Commun. 15, 10880 (2024)). Although a single-exponential decay\nmodel is not universally applicable to specific SOC-driven or HFI-driven spin-relaxation\nmechanisms, it is often a reliable approximation for the effective spin depolarization time within a\nlimited time window.\nSpecifically, we now explicitly define the spin-polarized transient absorption signal as the\ndifference between the photobleaching kinetics measured under opposite pump helicities while\nkeeping the probe helicity fixed, consistent with the experimental configuration shown in Fig. 2b:\n𝛥𝐴 𝑠𝑝𝑖𝑛 (𝑡)=𝛥𝐴 𝜎−𝑝𝑢𝑚𝑝,𝜎−𝑝𝑟𝑜𝑏𝑒 (𝑡)−𝛥𝐴 𝜎+𝑝𝑢𝑚𝑝,𝜎−𝑝𝑟𝑜𝑏𝑒 (𝑡)\nThe resulting spin polarization decay was fitted using a single-exponential function,\n𝛥𝐴 (𝑡)=𝐴 𝑒𝑥𝑝(−𝑡⁄𝜏 )\n𝑠𝑝𝑖𝑛 0 𝑠𝑝𝑖𝑛\nwhere 𝐴 denotes the initial spin-polarized bleach amplitude and 𝜏 represents the longitudinal\n0 spin\nspin lifetime. The extracted longitudinal spin lifetime of CH₃NH₃PbI₃ is 4.7 ps, whereas\nCD₃ND₃PbI₃ exhibits an extended lifetime of 12.4 ps, corresponding to a 2.6-fold enhancement.\nThese definitions and the fitting function are now explicitly stated in the main text (Lines 244–\n252).\nSecond, we agree that the magnetocurrent (MC) in a vertical spin-valve device is a device-level\nobservable and is therefore subject to additional extrinsic influences beyond the comparatively\nintrinsic spin depolarization dynamics probed by circularly polarized transient absorption. In\nparticular, MC is governed not only by the bulk spin diffusion length, but also by electrode spin\npolarization, interfacial spin transparency (spin-memory loss), and possible resistance mismatch or\nspin-independent leakage pathways, as captured by modified Jullière/Valet–Fert-type descriptions.\nUsing the experimentally determined diffusion coefficient D and the optically extracted\nlongitudinal spin lifetime τ , we estimate 𝜆 =√3𝐷𝜏, yielding λ ≈ 44.6 nm for CH NH PbI\nspin 𝑆 s 3 3 3\nand λ ≈ 70.1 nm for CD ND PbI .\ns 3 3 3\nIn the device geometry, the bulk spin survival across a spacer of thickness d can be expressed as\n𝑆(𝑑)=𝑒𝑥𝑝[−(𝑑−𝑑 )/𝜆 ]\n0 𝑆\nAs representative examples (neglecting the small interfacial correction d for simplicity), the\n0\nsurvival increases from ~0.64 to ~0.75 at d = 20 nm and from ~0.41 to ~0.56 at d = 40 nm upon\ndeuteration, indicating a substantially higher fraction of spins reaching the detector electrode.\nImportantly, this moderate increase in bulk survival is not expected to solely determine the MC\nmagnitude; rather, it helps move the device from a near-threshold regime to a robust detection\nregime in which the interfacial spin polarization and spinterface effects can manifest in the\nmeasured MC. In the non-deuterated device, stronger bulk spin loss together with\ninterfacial/transport losses can suppress the spin signal to the noise/background level (<1%),\nwhereas deuteration suppresses bulk spin relaxation and enables sufficient spin survival across the\nspacer, leading to a clearly resolvable room-temperature MC (~17.5%).\nQuestion 2-2\nFigure 3 shows that the difference in mobility between the protonated and deuterated samples is\nextremely small - approximately 6%, well within typical sample-to-sample or measurement\nvariation. Nonetheless, the authors interpret this minor change as evidence for increased scattering\ndue to vibrational suppression. This interpretation is not supported by the magnitude of the\nobserved variation, which is too small to draw conclusions about altered scattering mechanisms.\nA more reasonable interpretation is that deuteration has minimal influence on carrier mobility.\nThe manuscript should avoid overstating the physical significance of such a small variation unless\nstatistical evidence (error bars, repeated measurements) is presented to justify it.\nAnswer:\nWe thank the reviewer for this constructive comment. To address this concern, we performed\nadditional measurements and provide the statistics in Supplementary Fig. 14. The extracted\nmobilities are 54.9 ± 1.1 and 51.3 ± 1.6 cm² V⁻¹ s⁻¹ for CH₃NH₃PbI₃ and CD₃ND₃PbI₃,\nrespectively (mean ± s.d.). The mobility therefore remains comparable (~50 cm² V⁻¹ s⁻¹) in both\nfilms, indicating that deuteration has only a very limited impact on charge transport.\nTo avoid potential ambiguity, we revised the corresponding description in the main text (Lines 305\n–311) to adopt a more conservative interpretation and removed overly strong mechanistic\nwording.\nQuestion 2-3\nThe spin photovoltaic effect (S-PV) is one of the central claims of this manuscript. However, the\nexplanation provided in Figure 4a is conceptual only, and the manuscript does not present any\nquantitative model that can logically connect the schematic to the experimental results in Figures\n4b, 4c, or 4f.\nIn particular, the following questions remain unanswered:\n- Quantitative analysis about the total current reverse sign as illumination increases?\n- Quantitative analysis about that the parallel and antiparallel configurations yield different\nphotovoltages\n- Under what specific bias–illumination conditions can the authors tune the output current\nexactly to zero?\n- How much carrier reflection or suppression occurs in the antiparallel configuration, and what\ndetermines this magnitude?\nAll of these effects are described qualitatively but not supported by a quantitative charge-transport\nor spin-dependent recombination model. For a claim as central as a room-temperature S-PV effect,\nat least a minimal theoretical framework is required to justify the physical interpretation and\ndistinguish this work from prior studies.\nAnswer:\nThanks very much for reviewer’s comments. To systematically address the reviewer’s questions\nand to provide a deeper description of the spin photovoltaic mechanism, we have included a\ncorresponding schematic. First, under illumination, charge separation occurs in the perovskite\nlayer, generating a photocurrent (Supplementary Fig. 15a,b). We then apply an external bias\nopposite to the photovoltage. Because the directions of the applied voltage and the photovoltage\nare opposite, the total device current shifts with changes in either the applied bias or the light\nintensity, and can cross zero.\nHowever, since the spin valve employs ferromagnetic electrodes, sweeping the external magnetic\nfield reverses the magnetization of the electrodes at their respective coercive fields, producing\nparallel and antiparallel spin configurations. In the parallel configuration, the bias-injected spin\ncurrent can traverse the Co electrode with minimal scattering (Supplementary Fig. 15c,d). In\ncontrast, in the antiparallel configuration, enhanced spin scattering requires a larger applied\nvoltage in the I–V measurement to compensate for the scattering-induced reduction in current\n(Supplementary Fig. 15e,f). As a result, 𝑉 >𝑉 . Importantly, the material itself does not\nOC,AP OC,P\nchange during this process, and the intrinsic photovoltage of the perovskite layer remains\nunchanged. The main text section on the room-temperature spin photovoltaic effect has also been\nupdated with the detailed revisions described above, specifically in lines 340–362.\n- Quantitative analysis about the total current reverse sign as illumination increases?\nAnswer:\nThanks very much for reviewer’s comments. From a quantitative perspective, the device exhibits\na photovoltage of 18.4 mV, which is opposite in direction to the applied bias. Consequently, the\ntotal device current varies with either the illumination intensity or the applied bias. As shown in\nFig. 4b, under a fixed external bias of 10 mV, increasing the illumination drives the total current\ntoward the negative direction, forcing it to cross zero and reverse sign. Conversely, at fixed\nillumination, increasing the applied bias shifts the current toward the positive direction, again\ncrossing zero and switching its sign. In essence, once the applied bias exceeds 18.4 mV, the total\ndevice current remains positive.\nQuantitative analysis about that the parallel and antiparallel configurations yield different\nphotovoltages\nAnswer:\nThanks very much for reviewer’s comments. During the switching between the parallel and\nantiparallel magnetic configurations, the device structure remains unchanged, and the perovskite\nlayer in the middle experiences no modification. Therefore, the photovoltage remains constant at\n18.4 mV. The apparent difference in the photovoltage between the antiparallel and parallel states\narises from spin-dependent scattering: once the magnetization of the ferromagnetic electrodes\nreverses, the spin current experiences additional scattering during transport. As a result, a larger\nexternal bias is required to compensate for this extra voltage when sweeping the I–V\ncharacteristics.\nThe magnitude of this scattering-induced voltage primarily depends on the proportion of spin\ncurrent within the total current; a higher spin-current fraction necessitates a larger compensating\nbias. The spin-current fraction is governed by several factors, including the spin polarization of the\nferromagnetic electrodes, the spin-diffusion properties of the transport medium, as well as the spin\nlifetime and carrier mobility.\n- Under what specific bias–illumination conditions can the authors tune the output current\nexactly to zero?\nAnswer:\nThank you for the reviewer’s suggestion. To provide a clearer understanding of how the output\ncurrent is tuned, we have added Fig. 4f, which shows the bias voltage and illumination intensity\ncorresponding to the zero-current condition. It can be clearly seen that, as the applied bias\nincreases, a correspondingly higher illumination intensity is required to generate a larger\nphotovoltaic voltage that compensates the applied bias. Therefore, achieving an exact zero output\ncurrent is critically dependent on a specific combination of illumination intensity and bias voltage.\nHow much carrier reflection or suppression occurs in the antiparallel configuration, and what\ndetermines this magnitude?\nAnswer:\nThanks very much for the reviewer’s professional comments. In the antiparallel configuration, the\nmagnitude of carrier scattering is effectively captured by the magnetocurrent variation, denoted as\nΔIout, as shown in Fig. 4d. The magnitude of this variation is governed by the overall device\nperformance, including the Curie temperature and spin polarization of the electrodes, the carrier\nmobility and spin relaxation time of the semiconductor, the interfacial spin properties, the applied\nbias, and related factors.\nQuestion 2-4\nThe authors argue that the increase in spin lifetime due to deuteration leads to an enhancement in\nphotovoltage and S-PV contrast. However, photovoltaic voltage is influenced by multiple factors -\nrecombination dynamics, interfacial energetics, spin-selective reflection, and charge-transport\nasymmetry - and the manuscript does not demonstrate how the longer spin lifetime affects these\nparameters.\nIn its current form, the manuscript presents the argument in a purely qualitative manner, without\nexplaining the mechanism by which enhanced spin lifetime translates into measurable shifts in\nphotovoltage between the parallel and antiparallel configurations. To claim a fundamentally new\nS-PV mechanism enabled by isotope engineering, the authors must provide a more rigorous,\nmodel-based discussion linking the observed spin dynamics to the photovoltaic response.\nAnswer:\nThank you for the reviewer’s helpful comment. We apologize that our wording may not have\nbeen sufficiently clear and could have led to this misunderstanding. Our intention is to emphasize\nthat deuteration enhances the spin lifetime and thereby improves spin-dependent device\nperformance; we do not mean to claim that deuteration increases the intrinsic photovoltaic voltage.\nThe measurable photovoltage difference between the parallel and antiparallel magnetic\nconfigurations primarily originates from the magnetocurrent-related voltage component under the\nmeasurement condition, rather than from a genuine change in the built-in photovoltaic voltage.\nTherefore, this effect should not be attributed to isotope engineering.\nThis work offers an intriguing direction by combining isotope engineering with perovskite\nspintronics, and the experimental results are potentially impactful. However, the central claims -\nparticularly those related to spin lifetime extraction, spin diffusion length relevance, spin\nphotovoltaic operation, and the mechanistic role of deuteration - are supported primarily by\nqualitative descriptions rather than quantitative or model-based analysis.\nTo meet the standards of Nature Communications, the manuscript requires substantial\nstrengthening of its physical arguments and quantitative justification. A more rigorous analytical\nframework is essential for clearly establishing the novelty and validity of the reported phenomena.\nAnswer:\nWe thank the reviewer for the constructive and insightful comments. In response, we have\nsubstantially revised the manuscript to address all of the issues raised above. Specifically, we have\nadded detailed discussions and clarifications regarding spin lifetime extraction, the relevance of\nspin diffusion length, the operation of the spin photovoltaic effect, and the mechanistic role of\ndeuteration. Where appropriate, we now explicitly describe the quantitative relationships\nunderlying these phenomena. In addition, we have introduced more detailed schematic and\nmechanistic models to clarify aspects that were previously unclear. We hope that these revisions\nsignificantly improve the rigor of the physical arguments and enable a clearer understanding for\nthe reader.\nReviewer #3 (Remarks to the Author):\nIn this manuscript, the authors present compelling and somewhat unexpected results regarding\nspin transport in hybrid organic–inorganic perovskites (OIHPs). They synthesize both single\ncrystals and thin films of CH3NH3PbI3 and its deuterated analogue (CD3ND3PbI3), and\ndemonstrate that spin transport is dramatically enhanced in the deuterated compound. The\nstructural characterization is thorough and convincingly shows that the two materials are nearly\nidentical from the perspective of crystallography and electronic structure, while their vibrational\nspectra differ substantially. In addition, the charge-carrier mobility, determined via transient\nreflectivity microscopy, is comparable in both systems, suggesting similar charge-transport\nmechanisms.\nThe authors therefore conclude that spin transport is primarily influenced by hyperfine interactions\n(HFI) originating from hydrogen nuclei in the organic cation, rather than by differences in\nstructure, defects, or charge mobility. The demonstration of a room-temperature spin photovoltaic\neffect in deuterated perovskite spin valves adds multifunctionality and further strengthens the\nsignificance of the work.\nOverall, the manuscript is interesting and the results will likely attract the attention of the Nature\nCommunications readership. However, I have several points that require clarification before the\npaper can be considered for publication:\nWe thank the reviewer's positive assessment of our work and recommendation for publication.\nAnd, the related comments are addressed in detail below.\nQuestion 3-1\nAs the authors themselves note, HFI from hydrogen in OIHPs is typically considered negligible\ncompared to the strong spin–orbit coupling of the Pb–I sublattice, which is thought to dominate\nspin dephasing. Here, the experimental data clearly show that suppressing HFI via deuteration has\na dramatic impact on spin lifetime and spin transport. I think the authors should elaborate—at least\nqualitatively—on why hydrogen HFI is not overshadowed by SOC-induced mechanisms in this\nsystem. A conceptual or semi-quantitative discussion would be helpful, even if tentative.\nAnswer:\nWe thank the reviewer for this insightful comment. We agree that, in lead-halide perovskites, the\nstrong Pb–I spin–orbit coupling (SOC) is generally expected to make SOC-driven Elliott–\nYafet/D’yakonov–Perel’ (EY/DP) processes central to spin decay for itinerant carriers (Nat.\nCommun. 15, 188 (2024)). Our results do not suggest that hydrogen hyperfine interaction (HFI)\nreplaces SOC; rather, they indicate that a nuclear-spin-related contribution can remain\nexperimentally visible in the hybrid system and can be selectively tuned.\nA key distinction is that organic–inorganic hybrid perovskites introduce material ingredients that\nare absent (or strongly reduced) in fully inorganic analogues. First, hybrids exhibit a soft lattice\nand pronounced dynamic disorder/carrier–lattice coupling (Chem 4, 2826–2843 (2018)). Second,\nby composition they incorporate organic cations containing abundant ^1H nuclear spins (e.g., MA\n= CH₃NH₃⁺ and FA = (NH₂)₂CH⁺), which are absent (or greatly reduced) in fully inorganic lead-\nhalide perovskites (Nat. Rev. Mater. 1, 15007 (2016)).\nIn realistic films/devices, carriers are not always purely itinerant in the ideal bulk sense. If injected\nelectrons/holes (or polarons) have any wavefunction overlap with regions influenced by the\norganic sublattice—particularly in localized/trapped/polaronic states near interfaces—hyperfine\nfields can become non-negligible. In such situations, the apparent DP/EY relaxation can be\npartially masked, and the measured decay time can reflect an effective depolarization time that\nalso involves trapping/detrapping dynamics and inhomogeneous broadening.\nTo make the coexistence of SOC and HFI transparent at a semi-quantitative level, we write the\nspin-polarization decay as 𝑆(𝑡)=𝑆 𝑒−𝑡/𝜏𝑠 , where Γ≡1/𝜏 is the spin-decay rate. If two\n0 𝑠\nindependent channels contribute to an approximately exponential decay, their effects add at the\nlevel of rates (Matthiessen-like rule), giving Γ =Γ +Γ , i.e.\ntot SOC HFI\n1 1 1\n= + .\n𝜏 𝜏 𝜏\n𝑠 SOC HFI\nThis rate-based viewpoint is consistent with standard spin-dynamics treatments in which nuclear\nspins enter as an effective hyperfine (Overhauser) field with temporal fluctuations; fast motion can\nreduce the net hyperfine contribution in some limits (motional narrowing) but does not render it\nstrictly zero (Phys. Rep. 493, 61–236 (2010)).\nConsistent with this framework, perovskite-specific experiments have shown that\nhyperfine/nuclear-spin fields can measurably affect carrier-spin dynamics—for example,\nmodifying spin-polarization decay and inducing spin precession under appropriate conditions—\ndemonstrating that nuclear-spin effects need not be fully “washed out” even in lead-halide\nperovskites with strong SOC (Phys. Rev. B 110, 235301 (2024); Adv. Mater. 34, 2105263 (2022)).\nIn our work, deuteration selectively weakens the nuclear-spin-related term without intentionally\naltering the Pb–I framework, and the resulting 2.6-fold increase in 𝜏 indicates that the HFI-related\n𝑠\nchannel contributes a non-negligible fraction of the total rate while coexisting with EY/DP. We\nhave added a qualitative discussion along these lines in the revised manuscript (Lines 100-106 and\n254-258).\nQuestion 3-2\nIn Fig. 1f,g, the magnetocurrent is presented, but no information is given about comment on the\nabsolute device resistance would be important—does deuteration affect the resistance or RA\nproduct?\nSimilarly, in Fig. 10c (Supplementary), MC is shown as a function of OIHP thickness. It would be\nimportant to show or at least comment on how the resistance evolves with thickness. One would\nexpect a significant increase. Is it the case?\nAnswer:\nThanks very much for the reviewer’s comments. To the best of our knowledge, there have been\nno reports indicating that deuteration has a measurable impact on the electrical resistance of\ndevices. In our study, we extracted the resistance–area (RA) product of the devices shown in Fig.\n1f and Fig. 1g. The RA value of the deuterated CD₃ND₃PbI₃ device (Fig. 1f) is 0.712 MΩ·mm²,\nwhile that of the hydrogenated CH₃NH₃PbI₃ device (Fig. 1g) is 0.785 MΩ·mm². These values are\nvery close to each other and do not exhibit any noticeable difference, indicating that deuteration\ndoes not significantly affect the device resistance or RA product.\nIn addition, to address the reviewer’s concern regarding the device resistance at different film\nthicknesses, the corresponding data are provided in Figure R1. As shown, the resistance–area\n(RA) product indeed increases significantly with increasing OIHP film thickness.\nFig. R1. | Area-specific resistance of devices with different perovskite layer thicknesses.\nQuestion 3-3\nThe authors estimate the spin diffusion length for the deuterated compound based on tau and D.\nCan a similar estimate be provided for CH NH P bI ?\n3 3 3\nAnswer:\nThanks very much for the reviewer’s comments. Based on the measured spin lifetime and\ncarrier mobility, we estimated the spin diffusion length of CH₃NH₃PbI₃ to be λ ≈ 44.6 nm.\nHowever, due to the very weak MR signal in CH₃NH₃PbI₃, reliable extraction of the thickness\ndependence is not feasible, and therefore these results are not included in the main text.\nQuestion 3-4\nHow is the thickness controlled or monitored across samples? Via spin-coating parameters?\nProfilometry? Ellipsometry? More detail would help assess reproducibility of the thickness-\ndependent measurements.\nAnswer:\nThe perovskite film thickness was controlled by tuning the precursor solution concentration (7–\n30 wt%) and the spin-coating speed (2000–8000 rpm). The final thicknesses of the films were\nmeasured and verified using spectroscopic ellipsometry and atomic force microscopy (AFM).\nThese details have now been incorporated into the film preparation procedure in the Methods\nsection.\nFig. R2. | Thickness of films spin-coated at different rotation speeds using a 20 wt% precursor\nsolution.\nQuestion 3-5\nIt is unclear whether the measurements in Fig. 2 and Fig. 3 were performed on thin films or single\ncrystals. Since spin dynamics and carrier mobility can differ significantly depending on\nmorphology, the authors should state explicitly which type of sample was used in each\nmeasurement.\nAnswer:\nThanks very much for reviewer’s comments and we agree with the reviewer. To ensure a\nconsistent evaluation of the perovskite film properties, all measurements presented in Figures 2\nand 3 were performed on polycrystalline films prepared under identical processing conditions,\nincluding the precursor solution concentration and film thickness. This approach not only\nguarantees internal consistency but also ensures that the measured properties closely reflect those\nof the films used in the actual devices.\nIn summary, I find this to be an interesting piece of work with strong potential impact. Addressing\nthe points above would significantly strengthen the manuscript and improve its clarity.\nAnswer:\nWe thank the Reviewer for their positive assessment of our work and recommendation for\npublication.\nReviewer #3 (Remarks to the Author):\nThe authors have satisfactorily addressed all my concerns. The new data significantly\nimprove the quality of the manuscript and clarify the points I had raised. I therefore\nrecommend the publication of this work.\nAnswer: Thank you very much for your very positive comments."}, {"round": 2, "reviewer_comments": {"reviewer_3": "The authors have satisfactorily addressed all my concerns. The new data significantly improve the quality of the manuscript and clarify the points I had raised. I therefore recommend the publication of this work."}, "author_response": "Answer: Thank you very much for your very positive comments."}]

Decision letter