Chirality transfer from chiral perovskite to molecular dopants via charge transfer states

Domain: biology
Published: 2026-03-10
Editorial outcome: major_revision

Abstract
Chiral perovskites are semiconductors with broken mirror symmetries. Their photo responses are often
constrained in the UV range. In this work, we demonstrate that doping 2,3,5,6-Tetrafluoro-7,7,8,8-
tetracyanoquinodimethane in the chiral perovskite matrix introduces a visible light absorption feature
through the emerging charge-transfer electronic states. These charge-transfer states exhibits circular
dichroism inherited from the chiral host, indicating effective chirality transfer from host to guest
component via electronic coupling. Quantum-chemical modeling identifies a strong wave function
overlap between an electron and a hole of the guest-host in a closely packed crystal configuration
promoting the charge transfer state’s optical activity. We further integrate the doped chiral perovskite film
into photodetectors and demonstrate a selective detec tion of circularly polarized light in both UV and
visible regions. Our results suggest a universal approach of introducing visible photo absorption states to
the chiral matrix to broaden the optical active range while enhancing the electrical conductivity.

Introduction
Chirality is an important symmetry property of molecular systems1: A chiral molecule cannot be
superimposed on its mirror image, which breaks the molecule’s inversion symmetry2. Semiconductors
crafted in chiral structures have preference to absorb photon with the same chirality. Additionally, chiral-
induced spin selectivity effect3, 4 is proposed in the chiral semiconductors which can discriminatorily
transport spin-polarized carriers5, 6. These properties are highly promising for photo-detectors and imaging
that can distinguish the polarization states of photon7.

There are few types of chiral semiconductors that have drawn extensive attention, such as chiral
small molecules and polymers8-10, quantum dot assembly11, 12, organo-inorganic hybrids13-15 and meta
surfaces 16, 17. The organic chiral semiconductors synthesized in helix structures can deliver strong
anisotropy with a typical anisotropic factor of circular dichroism (g
CD
) in the range of 0.001 to 0.2 with a
few exceptionally high values above 0.5 up to 1.218-21. However, the helix organics require intense
synthetic approaches to obtain a highly asymmetric structure. The electrical conductivities are often low
in organic materials, limiting their performances as a photo-detector.

Hybrid organo-inorganic chiral structures can accomodate a wide tunability in the local structure
with tunable optoelectronic properties. Chiral perovskites are one of hybrid semiconductor systems that
have shown great promise for photon detections22-25. A typical chiral perovskite structure with commonly
used chiral ligands is illustrated in Fig. 1a, where chiral organic molecules incorporated into lead-halide
octahedrons (PbX ) drive the rotations of the PbX cages following the chirality of the molecules as shown
6 6
in Figure 1a. The dipole moment of the excited states thus orients with the helix PbX rotation direction
6
to impose optical selectivity to circular polarization state of photons26. With strong circular dichroism
(CD) demonstrated13, 14, 27-30 chiral perovskites were integrated into photodetectors for the direct detection
of circularly polarized light. The photo detectors were capable of differentiate the handness of the
incoming circularly polarized light by its distinct change in photoconductivity, delivering anisotropic
factors of 0.1 ~ 0.222, 30-33. Circularly polarized light emission from the chiral perovskites was also
possible31, 34, 35, which are promising photonic sources with polarized states. Very recently, zero-
dimensional In based hybrid chiral structures have been demonstrated for exceptional polarized
pohotoluminescence with strong intensity 36.

While these pioneer demonstrations open new avenues for chiral opto-electronics, the organics in
the chiral perovskites were considered insulators that add barriers to the electrical conduction of the charge
carriers37-39. Chiral perovskites are typically low-dimensional structures 40-42 that underpin quantum
confinement. Consequently, chiral perovskites have a wide optical band gap and limited responsivity to
visible light. Due to their low conductivity and lack of photo-activity in the visible range, low dimensional
chiral perovskite materials face significant limitations in their potential electronic applications. Displayed
in Fig. 1b, we summarized the reported g and their absorption cut off wavelength of the photo-detectors
ph
made with organic, hybrids and metal nanostructured materials 7, 8, 18-21, 30, 43-59. Most of the organic and
hybrid chiral semiconductors show an absorption cut-off between 400 nm to 550 nm. The meta-surfaces
of metallic nano-structures are one of the active research areas, they are not semiconductor type but also
deliver high performance mostly in the near-IR range. Noticeably, there is a gap between 600 nm to 1,000
nm where only few chiral semiconductors are developed for detector. To bridge this gap, several studies
have attempted to extend the absorption range via different mechanisms. For example, Peng et al 60
employed a two photon absorption mechanisms to upconvert the photon via a chiral perovskite media.
With this mechanism, they have demonstrated a dual modal circularly polarized light detector with visible
light (520 nm) and NIR light (800 nm). Another report by Yang et al 61 investigated a hetero-structure
formed by a 2D chiral perovskite interfaced with a 3D bulk film. This structure enabled spin filtering
across the interface that promoted the photocurrent produced by photon with a certain polarization state.

Here we investigate a molecular dopant into the chiral perovskite matrix to extend the circularly
polarized photon absorption into the visible range via a photo active charge transfer state. By mixing
2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) molecules into the chiral perovskite
matrix, we observe the emergence of an optically active charge transfer state formed between the chiral
perovskites host and the F4TCNQ guest, which adds a visible absorption band in the 550-750 nm
wavelength range. Interestingly, both the intrinsic absorption band from the perovskite matrix and the
charge transfer absorption feature exhibit circular dichroism, indicative of a chirality transfer from the
host to the guest. Transient absorption spectroscopy confirms the presence of charge transfer states at the
interface. Furthermore, atomistic time-dependent density functional theory (TDDFT) simulations of the
chiral perovskite/F4TCNQ interface corroborate the experimental observations. Specifically, our
calculations suggest that substitutional doping of F4TCNQ enhances electronic coupling leading to the
formation of optically bright charge-transfer states. The closed packed crystal structure is further observed
in the gracing incident X-ray scattering pattern where a large lattice feature was observed corresponding
to the intercolation of F4TCNQ between the perovskite chain. Finally, we demonstrate the direct detection
of circularly polarized light by integrating our host-guest structure in a photo-detector. Due to the chirality
transfer, our detector can discern the chirality of photon across both the blue and visible spectral ranges.
Altogether, our findings suggest a general approach for chirality transfer from the host matrix to the guest
dopant via an electronically coupled charge transfer state.

Results
Circular dichroism of chiral perovskite
We start with synthesizing chiral perovskite structure using chiral enantiomer ((S)-1-Methyl-2-
pyrrolidinemethanol and (R)-1-Methyl-2-pyrrolidinemethanol) as shown in Fig. 2a. The chiral
perovskites are named S-MP and R-MP thereafter for convinence. The material growth procedures are
detailed in the Method Section. Following material synthesis and recrystallization, we obtain needle-like
palm-yellow single crystals (Supplementary Fig. 1), indicative of a 1D structure formation. We further
investigate the crystal structure by growing single crystals and conduct single crystal diffraction (Fig. 2b).
After crystal structure refinement, we find that R-MP perovskite crystallized in the chiral space group
P2 2 2 (space group 19), a Sohncke space group. The detailed crystal structure information is
1 1 1
summarized in Supplementarl Table-1 and Supplementary Fig. 2 in the SI.

We next design model simulations to gain atomistic insights into the chirality property of the obtained
crystals. Our approach addresses two fundamental aspects: the chirality of the PbI sublattice48 and
6
chirality transfer via electrostatic interactions with the chiral molecules62, 63. Specifically, to simulate the
circular dichroism (CD) spectrum using TDDFT methodology, we construct our computational model
from a finite fragment of the perovskite crystal structure, based on available crystallographic data. To this
framework, we append either an achiral methylpyridinium (MP) cation or its chiral R-/S-enantiomers.
The models are briefly outlined in the Supplementary Methods Section. As a control, we also calculate
the CD spectrum for the perovskite synthesized with the achiral MP molecule using a published crystal
structure file (Supplementary Fig. 2)64. Fig. 2c displays the computed CD spectra, which reveals that the
perovskite synthesized with chiral MP exhibits much enhanced CD intensities whereas the structure
synthesized with achiral MP shows negligible signal. Note that our model is built by modeling a fragment
of the crystal. The calculated absorption onset (~ 300 nm) is blue-shifted relative to experiment (~ 400
nm), primarily due to the finite size of the modeled nanowire, which introduces artificial quantum
confinement. Moreover, there is a well known optical gap dependence on choice of the hybrid density
functional (Supplementary Fig. 3). Additionally, the unresolved positions and orientations of the chiral
molecules in the crystallographic data limit direct spectral comparison.

Nonetheless, the calculations reproduce the key qualitative feature, the enhanced CD response observed
for the chiral perovskite (Fig. 2c) compared to the achiral analog, consistent with chirality transfer from
the organic to the inorganic components. This result supports the concept of chirality transfer from a chiral
molecule to the 1D crystal structure of the perovskite. In our case, a structural chiral distortion in the PbI
6
1D chain is identified as a dominating mechanism. We also model the CD spectrum when chiral MP are
placed on the surface the perovskite lattice without driving the PbI cage rotations. If the chirality transfer
6
is mediated by electrostatic interactions we would expect to see mirrored CD spectrum when comparing
models containing the MP enantiomers. We find that their CD spectrum are nearly identical and only
slightly deviate from the bare perovskite (Supplementary Fig. 3). This comparison further confirms that
the CD originates from the chirality imprinted in the PbI inorganic lattice driven by the chiral MP
6
molecules.

In Fig. 2c, we observe a small but non-zero CD signal from the non-chiral perovskite structure. This
response originates not from intrinsic chirality, but rather from the finite size of the perovskite fragment
used in our simulations. Specifically, the finite fragment breaks translational symmetry, introducing edge
effects that, in our case, lead to a breaking of inversion symmetry. As a result, a weak CD signal emerges
even in an achiral system. This behavior is distinct from previous reports in the literature65-67, where weak
CD responses in achiral perovskites have been attributed primarily to the Rashba effect, arising from spin–
orbit coupling and structural asymmetry at the atomic scale.

We next experimentally measure the CD and absorption spectra of the perovskite thin films under
illumination with left-handed and right-handed circularly polarized light as summarized in Fig. 2 d-f. The
achiral counterpart is also measured as a comparison. Fig. 2d is the photograph of the obtained solutions.
With F4TCNQ, the solution turns into a bright green color, different from either pristine solution.
F4TCNQ dopant is known for its strong electron-accepting ability due to its electron-deficient nature. As
illustrated in Fig. 2d, the energy level of the pristine perovskite and F4TCNQ is illustrated based on the
UPS measurement (Supplementary Fig. 4). The new absorption feature is attributed to the charge-transfer
(CT) state formed at the donor-acceptor interface, as documented by prior reports on organic systems
doped with F4TCNQ 68-70. CT states represent electronic excitations in which the photoexcited electron
and the corresponding hole become localized on different fragments or regions of a molecular or hybrid
system. Such states play a critical role in processes such as photoinduced charge separation, energy
transport, and dopant–host interactions. The defining characteristic of CT states is the spatial separation
between the electron and hole, which often leads to weak Coulomb interaction and reduced wavefunction
overlap. As a result, CT transitions typically exhibit small transition dipole moments and low oscillator
strengths, rendering them optically dark in many systems. However, when strong electronic coupling or
orbital hybridization exists between the donor and acceptor components, the electron–hole overlap can
increase, giving rise to CT excitations with noticeable optic activity.

We next spin coat thin films with these solutions and then annealed them at 100 ºC for 10 minutes.
Like the solution, the pristine chiral perovskite thin film has a transparent yellow color, whereas the doped
film exhibits a green color (see film photo shown in Supplementary Fig. S1). Fig. 2e shows the CD and
absorption spectra of the pristine and doped S-MP and R-MP chiral perovskite thin film. The pristine films
exhibit two derivative shaped CD features crossing zero at 360 nm and 390 nm, corresponding to the two
absorption peaks of the perovskite material. Near the absorption peak, the R-MP (S-MP) sample exhibits
a negative (positive) CD at higher energy and a positive (negative) feature at lower energy, manifests a
Cotton effect52, 71. To eliminate the influence of the linear dichroism, linear barefringes, we test the CD
spectra by rotating the samples at 180 degrees with respect to the incident light 52, 72. The results are shown
in Supplementary Fig. 5-7. The CD signature of F4TCNQ only thin film is presented nin Supplementary
Fig. 8 where no CD is observed. Next, F4TCNQ is added to the precursor, with the weight percentage
varied from 0.1% to 5%. The achiral MP thin film has a similar absorption spectra as the chiral films. It
is interesting to note that the CT state absorption is almost negligible in the 1% F4TCNQ doped A-MP
perovskite thin films. After analyzing the crystal structures with different dopant levels comparing chiral
and achiral samples (see Supplementary Fig. 9 - 11), we think the molecular incorporation into the lattice
is different in A-MP sample that contributes the difference in CD. More detailed discussions are provided
towards the end of this paper.

Fig. 2f shows the CD spectrum of the F4TCNQ doped chiral perovskites thin film. Here CD
signals emerge near the absorption peaks of the perovskite band edge and broaden towards 416, along
with a broad visible light absorption emerging between 550 nm and 750 nm, which contributes to the
green color observed in the film. The dopant dependent absorption and CD are investigated and illuatrated
in Supplementary Fig. 12. The peak position of the CT state remain unchanged, while the magnitude of
the absorption and CD increase with higher doping levels. The fact that CD signals are also detected near
the broad peak in the 550 nm to 750 nm range suggests the hypothesized charge-transfer states also inherits
the chiroptical properties from the perovskite. In contrast to the chiral structures, the doped achiral
structure does not exhibit CD in the longer wavelength range.

Carrier dynamics
To elucidate the electronic transitions associated with the different absorption features, we perform
femtosecond pump-probe Abroadband transient absorption spectroscopy (TAS) on both pristine and doped
thin-film samples. From the spectra and kinetic analysis of each peak in the TAS spectrum, we confirm
the presence of charge-transfer coupling between the chiral perovskite and the F4TCNQ dopant.

The TAS spectra, probed at various delay times following the pump pulse for both samples, are
plotted in Fig. 3a-b. We use a 290 nm laser pump for excitation and a broadband source to probe the
transient absorption in the UV-Vis spectral region. The UV-Vis spectrum of F4TCNQ film is shown in
Supplementary Fig. 8 where its most pronounced absorption is centered around 350 nm ~ 400 nm.
Therefore, we select a 290 nm pump laser which primarily excites the chiral perovskite matrix while
avoiding direct excitation of the dopant. Therefore, any signal associated with the dopant would result
from electronic transitions coupled to the chiral perovskite host. In the TAS spectrum of the undoped
chiral perovskite displayed in Fig. 3a, a pronounced negative feature emerges at 390 nm within sub-
picosecond time range after pumping, which is attributed to the ground state bleaching73. A positive
feature near 360 nm and a weaker positive peak near 490 nm are also observed in this sample,
corresponding to photo-induced absorption transition in the high and low energy bands. In the doped
sample, the same ground state bleaching feature at approximately 390 nm is observed, along with an
additional negative peak at 416 nm, as shown in Fig. 3b. While pumping with 340 nm is possible, it yields
a different ground state bleaching feature of F4TCNQ only sample at around 600 nm (see Supplementary
Fig. 13-14). Therefore, the ground state bleaching at 416 nm in the doped sample originates from the
formation of the charge transfer state. Moreover, a pronounced positive photo-induced absorption peak is
observed in the doped sample between 500 nm and 600 nm. While this peak overlaps with a weak, broad
absorption band in the pristine sample probed by TAS, we attribute it to an electronic transition to a
different charge transfer excited state, due to its distinct vibronic shape and different recombination
kinetics, which will be discussed in the next paragraph.

We further analyze the kinetics of the ground state bleaching and photo-induced absorption
features for both samples, as shown in Fig. 3c-d. The 3D maps of the TAS spectra are shown in
Supplementary Fig.15-16. In Fig. 3c, we overlay the kinetic curves of the 390 nm peak for both the pristine
and doped samples. Noticeably, the decay curve of the pristine perovskite sample can be fitted by a double
exponential function, suggesting two predominant recombination pathways for the excited state relaxation
to the ground state. The pristine sample has a fast component with a time constant () of 9.01 ps followed
1
by a slow decay with a time constant () of 416.67 ps. The decay curve of the doped sample can be fitted
2
with the same function, yielding  = 16.13 ps and  = 303.03 ps for the fast and slow components,
1 2
respectively. The presence of the dopant in the perovskite matrix noticeably extends the short time
constant while shortening the long component. The short component  is typically assigned to exciton
1
diffusion74, 75. Thus, in presence of the charge-transfer state, the exciton diffusion lifetime is extended due
to charge separation. The long component is often attributed to charge recombination. The reduction in
2
 in the doped sample can be understood as accelerated electron injection back into the perovskite’s
2
valence band, which return the system to the ground state more quickly74.

In Fig. 3d, we compare the kinetics of the new negative peak at 416 nm and the new positive peak
at 510 nm with the ground state bleaching peak at 390 nm from the perovskite. The kinetics of the
F4TCNQ’s ground state bleaching peak are plotted in the same graph, when pumped by a 340 nm laser.
All curves can be fitted with two decay constants, as detailed in Table 1.

Table 1. Kinetic data extracted from the TAS results comparing pristine, doped perovskites and control
F4TCNQ samples.
Sample Peak (ps) (ps) k (ps-1) k (ps-1)
2 1 2 1
Undoped GSB 390 nm 416.67 9.01 0.0024 0.111
Doped GSB 390 nm 303.03 16.13 0.0033 0.062
GSB 416 nm 131.58 1.32 0.0076 0.758
PIA 510 nm 196.08 4.38 0.0051 0.228
F4TCNQ GSB 628 nm 1.53 0.19 0.6521 5.102
Both 416 nm and 510 nm peaks have  of 1.32 ps and 4.38 ps, respectively, followed by  of
1 2
131.58 ps and 196.08 ps. In stark contrast, the fitted  and of the F4TCNQ-only sample are extremely
1 2
short, at 0.19 ps and 1.53 ps, respectively. The slower decay behavior of the doped sample replicates the
kinetics of the perovskite host matrix, with lifetimes significantly shortened in presence of the dopant.
These results suggest that the new features at 416 nm and 510 nm do not represent the electronic
transitions within the F4TCNQ molecule itself but are associated with charge transfer and recombination
processes at the interface.

From the TAS data analysis, we conclude the charge transfer kinetics as the following. The chiral
perovskite matrix is first pumped, and charge rapidly transfer from the excited state of the chiral matrix
to the dopant at fast rate, with 1/k <1 ps. The new ground state bleaching and photo induced absorption
CT
features correspond to electronic transitions to the charge-transfer state. This indicates a strong interaction
between the donor (chiral perovskite, host) and the acceptor (F4TCNQ, guest) components.

Crystal structure and theory modeling
To gain insight into electronic features at the host-guest interface, we next perform quantum
chemical calculations (see Supplementary Methods) using two model structural arrangements of the guest
in the host matrix: In model-1, F4TCNQ is intercalated between the perovskite chains, while in model-2,
F4TCNQ substitutionally replaces the A-site cation (R/S-MP cations) in the perovskite structure, as
illustrated in the top panels of Fig. 4a-b, respectively. We comput the electronic structure of these systems,
focusing on the appearance of charge transfer excitations.

Crucially, we account for the dielectric effects of the perovskite lattice using state-specific
solvation models, which are known to significantly influence the transition energies of charge-transfer
states, as detailed in Methods section. The resulting simulated absorption spectra (black curve) along with
the contributing oscillator strengths (f ) of the two model composite systems, as well as isolated
ON
perovskite and F4TCNQ molecule, are plotted in the same graphs. Notably, Fig. 4a-b displays simulations
results from both state-specific non-equilibrium (CT, non-eq) and equilibrium (CT, eq) solvation. The
charge transfer peak in the computed absorption spectra exhibits a significant red-shift relative to the
excitonic absorption at the perovskite band edge for both models (particularly for equilibrium solvation),
in-line with experimental observations. Fig. 4c-d displays the natural transition orbitals (NTOs) of the
lowest excited state computed for models 1 and 2. NTOs decompose a given electronic excitation into its
constituent electron and hole orbitals 76. We observe distinct spatial localization of electron (on the
molecule) and hole (on the perovskite) orbitals in both models. This highlights that upon doping, the
electron transfers from the perovskite to F4TCNQ owing the election deficiency of the latter. In the ground
state our simulations indicate some partial electron transfer (~0.1e) supported by improved electrical
conductivity measurements discussed later. Upon optical excitation, more electronic density is getting
transferred to F4TCNQ (~1e) depending on a particular model structure. This confirms our assignment of
the red-shifted optical features to charge-transfer states introduced by the dopant molecule.

Importantly, the degree of electron transfer and the resulting modifications of the absorption
spectra significantly depend on the relative alignment of the perovskite and F4TCNQ. In model-2, when
the F4TCNQ dopant substitutes for A-site cations, the hole wavefunction becomes spatially delocalized
between the perovskite and the molecule, resulting in a notable overlap with the electron wavefunction.
Consequently, we observe a 20 fold enhancement in oscillator strength in Fig. 4b, whereas in model-1,
where the dopant is intercalated, the charge-transfer state is essentially optically dark, as shown in Fig.
4a. This can be explained by the enhanced electronic coupling when the dopant is closer to the perovskite
lattice leading to improved overlap of the electron and hole wavefunctions (Fig. 4c-d). Thus, our quantum-
chemical modeling suggests that a closely packed host-guest crystal structure will yield a bright charge
transfer state with non-vanishing oscillation strength.

Experimentally, we conduct structure characterization to probe the arrangement of the guest-host
thin film structures, with the results shown in Fig. 4e-f. Fig. 4e displays the X-ray diffraction (XRD)
patterns for F4TCNQ, undoped chiral perovskites, and the host-guest thin film. In the doped perovskite
sample, several peaks correspond to those of the pristine chiral perovskite XRD peaks, indicating the
presence of the host crystalline structure. Additionally, two new peaks appear at the lower angle range
that do not match either the host or guest crystal structures. These diffraction peaks correspond to a long-
range ordering of the crystalline structure. To examine the low angle peak more closely, we collect grazing
incidence wide-angle X-ray scattering (GIWAXS) to further map the new features (Fig. 4f) in 2D space.
The full images of R-MP and S-MP chiral perovskites, along with those with dopants, are shown in
Supplementary Fig. 17. In the pristine film, we identify the main (011) and (020) peaks at 0.68 Å-1 and
0.73 Å-1, respectively. Upon doping, both peaks are weakened and broadened (see GIWAXS linecut in
Supplementary Fig. 18), indicating that the dopant introduces disorder into the perovskite matrix.
Consistently with the XRD patterns, two new peaks emerge at 0.46 Å-1 and 0.9 Å-1, corresponding to a d-
spacing of 13.78 Å and 6.98 Å, respectively. The ordered structures with d-spacings of 13.78 Å and 6.98
Å likely correspond to two F4TCNQ molecules (d = 7.3Å) stacked with intercalation 77 between two
perovskite chains. The F4TCNQ molecules gradually fill the space between neighboring perovskite
backbones, weakening the perovskite’s crystalline packing. It worth noting that the two new peaks in the
doped samples are predominately oriented along the out-of-plane directions, with an intense scattering
signal along the q direction. From the X-ray scattering analysis, we can conclude that F4TCNQ molecules
z
do not reside outside of the crystalline perovskite domains, but rather diffuse into the lattice, forming a
closely packed super molecular structure. This structure aligns with the scenario described in model-2,
where F4TCNQ is in a close contact with the PbI backbone, thereby introducing optically active charge
6
transfer states.

Photodetector demonstrations
Finally, we demonstrate a photodetector made with the guest-host chiral perovskite thin film for
the direct detection of circularly polarized light. The device structure and testing conditions are illustrated
in Supplementary Fig. 19. Fig. 5a shows the photocurrent changes with quarter wave plate rotation angle
respect to the linear polarizer’s direction. The incoming light is maintained at 45-degree angle with respect
to normal incidence to eliminate the preferential scattering effect of linearly polarized light by the
crystalline domains. The device made with R-MP-perovskite absorber shows stronger photocurrents when
the incoming light is left-handed circularly polarized (quarter wave plate is at 45o, 225o to the linear
polarizer’s axis), whereas the photocurrent produced by the right-handed circularly polarized light (when
the quarter wave plate is at 135o and 315o) is weaker. In contrast, the perovskite made with S-MP ligands
shows the opposite trend producing lower photocurrent in response to right-handed circularly polarized
light. Fig. 5b shows the photocurrent response of our R-MP perovskite detector when illuminated by
circularly polarized blue and red light sources (635 nm), with multiple on/off cycles. The photocurrent is
consistently enhanced across multiple cycles when the detector is illuminated by right-handed circularly
polarized light, suggesting an anisotropic detectivity. Interestingly, anisotropic detectivity is observed
when illuminated by both blue and red light, which excite the
intrinsic peak and charge transfer state respectively. The anisotropic factor (g ) is calculated to be 0.18
ph
and 0.12 for blue and red-light sources, respectively.

To understand the effect of the dopant on the material’s conductivity change, we measure the
temperature dependent current voltage curves of both devices in the dark. The results are shown in
Supplementary Fig. 20. We observe that the room temperature dark conductivity of the doped film is
improved by more than 2 orders of magnitude comparing to that of without dopant. Fig. 5c displays the
extracted dark current against 1/T. In both devices, the dark current grows exponentially with temperature,
suggesting a thermally activated transport mechanism attributed to the charge delocalization across
conducting sites. The thermal activation energy can determined by the Arrhenius equation. The device
with 1% F4TCNQ dopant has a lower activation energy (E = 350 meV) compared to the undoped device
A
(E = 480 meV). The F4TCNQ creates a conducting channel that facilitates electron hopping the through
A
the chiral perovskite matrix, thereby lowering the energy barrier. With a lower energy barrier for carrier
conduction, there is a higher chance of extracting the charge carriers from the material.

Next, we compare the performances of the pristine and doped by changing the absorber’s
thicknesses. Supplementary Fig. 21-26 present the photocurrent data collected from each device. We
extract the device’s responsivity (R in A W-1) as a function of chiral perovskite’s thicknesses and plot
them in Fig 5d-e, and Supplementary Fig 27 shows the device’s external quantum efficiency. When
illuminated by a blue light source, the undoped device shows a rapid raise in its R when the film thickness
increases from about 30 nm to 380 nm, due to improved photo absorption. However, its R begins to decline
with further increases in thicknesses over 400 nm owing to poor conductivity. In contrast, the R of the
doped device continuously increases with thickness and levels off around 800 nm, aided by the improved
conductivity. Fig. 5e illustrates the R when illuminated by a red laser, which excites the new charge
transfer absorption feature. This trend mirrors that observed with the blue laser: the R signal increases
with thickness benefitted from the higher electrical conductivity from doping.

Note that the photo-detectors’ responsivity and external quantum efficiencies are relatively low in our
work, which can be attributed to the unoptimized device structure and testing conditions. The interfaces
are not optimized for zero bias operation, there are limited charge collection without an internal electrical
field. In addition, the detectors are tested under unbiased condition to avoid large current injection through
the device. At a higher bias, the dark baseline are increased significantly that diminish the difference in
the photocurrent induced by the polarization of the light.

Fig. 5f-h show the photocurrent’s g factor (g ) as a function of layer thickness. Here we notice that the
ph
g changes with the absorber thickness. Interestingly, it changes in accordance with the photocurrent
ph
responsivity with thickness. In the pristine sample, the g first increases with thickness from 50 nm to
ph
380 nm. After 400 nm, the g starts to decay with higher thickness. According to the temperature
ph
dependent charge transport study presented in our Fig. 5c, the charge conduction in the chiral perovskite
polycrystalline thin film is dominated by the electron delocalization across disconnected sites. Increasing
the thickness of the material will hinder the charge transfer efficiency which thus introduce decoherence
of the spin polarized electron. Therefore, at a higher thickness, g decays because of a weakened
ph
circularly polarized photogalvanic (CPGE) effect 78, 79. In contrast, with F4TCNQ dopant, the conduction
barrier is reduced that facilitates the charge transport to the electrodes. As a result, the g can be
ph
maintained when the thickness increased beyond the 400 nm range.

The thickness dependence can be understood as the balance of the selective absorption and charge
scattering. The increase of g is likely from a stronger absorption and CD that improve the photocurrent
ph
selectivity. Another important contributor of the g is the coherent transport of the spin polarized carriers.
ph
Since the polarization induced photocurrent (or CPGE) is dependent on the sign of the spin polarized
electrons, the flipping of the spin will degrade the signal of the photocurrent.

Methods
Materials
Lead (II) iodide (99%), hydriodic acid (≥57.0 wt%), hypophosphorous acid (50 wt % in H₂O),
dichloromethane, and (S)-(−)-1-methyl-2-pyrrolidinemethanol were obtained from Sigma-Aldrich and
used without further purification. (R)-1-methyl-2-pyrrolidinemethanol was procured from Matrix
Scientific and used as received.

Synthesis of (R/S-MP)₂PbI
4
Lead (II) iodide powder (0.922 g, 2 mmol) was dissolved in 4 ml of 57% aqueous hydriodic acid and 1.0
ml of 50 w.t.% hypophosphorous acid. The mixture was heated with stirring at 130 °C for 10 minutes
until a clear solution was obtained. Subsequently, (R /S)-1-methyl-2-pyrrolidinemethanol (0.230 g, 2
mmol) was slowly added to the solution under continuous stirring. During the addition of the chiral
compound, yellow crystals immediately precipitated. These crystals were then dissolved in
Dimethylformamide at a concentration of 3 mg ml-1 and recrystallized using 15 ml dichloromethane at
room temperature by slow diffusion.

Thin film fabrication
To fabricate thin films, we dissolve the recrystallized perovskite crystal powder in DMF solvent at a
concentration of 50 mg ml-1. The dopant is added at a weight percentage of 1% relative to the weight of
the (R/S-MP)₂PbI . The obtained films are shown in Supplementary Fig. 1, the pristine films are pale
4
yellow whereas the doped films exhibit green color.

GIWAXS of thin films
GIWAXS measurements were conducted at beamline 17A of the National Synchrotron Radiation
Research Center (NSRRC) in Taiwan, utilizing a wavelength of 1.321184576 Å. Standard GIWAXS
patterns were obtained with an incident angle of 0.14°.

Ultraviolet photoelectron spectroscopy characterization
Our ultraviolet photoelectron spectroscopy experiments were carried out in an ultrahigh vacuum system
with base pressures < 2 x 10-9 Torr equipped a hemispherical electron energy analyzer (SPECS, PHOIBOS
100) and ultraviolet source (SPECS, 10/35). He(I) at 21.2 eV radiation was used . The angle between
the analyzer and UV- source is 45° and photoelectrons were collected along the surface normal direction
of the sample. The Fermi level of the spectra were calibrated vs the Fermi edge of Au(111) crystal.

Single crystal analylsis.
The datum crystal (0.19 × 0.155 × 0.136 mm3) was affixed to a MSiTeGen microloop with polybutene oil.
Diffracted X-ray intensities were measured with a RigakRu XtaLab Synergy-S diffractometer using a
PhotonJet-S microfocus X-ray source with Ag target (A g Kα λ = 0.56087 Å) and HyPix-6000HE hybrid
photon counting detector. An Oxford 1000 cryostream was used to maintain the sample at 290.0(1) K. A
series of ω scans were used to cover reciprocal space. Data reduction was performed using CrysAlisPro.82
Structure solution was performed via intrinsic phasing with ShelXT83 and full-matrix least-squares
refinement with ShelXL84 using Olex2.85 R-MP perovskite crystallized in the chiral space group P2 2 2
1 1 1
a Sohncke space group. Space group assignment was based on systematic absences, E2
statistics, and the successful refinement of the structure. Data collection, structure solution, and refinement
were challenging and are outlined below.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "Nie and her colleagues present a conceptually new study that combines theoretical calculations and experimental characterization to demonstrate charge-transfer-induced chirality transfer in F4TCNQ-doped chiral perovskite films. The authors show that doping with F4TCNQ introduces new electronic states in the visible range that inherit circular dichroism from the chiral host lattice. The mechanism is supported by quantum chemical modeling and transient absorption spectroscopy, and the functional implementation in CPL photodetectors further highlights the practical significance of the approach. I believe it may be suitable for publication in Nature Communications after the authors address the following comments.\n1, The authors claim in the introduction section and Fig. 1b that hybrid perovskites are not capable of detecting circularly polarized light beyond 550 nm. However, previous studies have already demonstrated vis–NIR CPL detection based on hybrid perovskites (e.g., J. Am. Chem. Soc. 2021, 143, 14077–14082; Nat. Commun. 2025, 16, 4161). These relevant works should be appropriately discussed to clarify the novelty of the current approach.\n2, On page 6, line 17, the authors write “Fig. 2b displays the computed CD spectra,” but Fig. 2b actually shows the crystal structure. Similarly, Fig. 2d is cited as showing the CD and absorption spectra of perovskite thin films, while it instead displays photos of precursor solutions. The authors should carefully check all figure citations to ensure consistency and accuracy.\n3, Fig. 2c shows a non-negligible CD signal for the non-chiral perovskite. What is reason for this phenomenon? Could this be attributed to Rashba effect, as previously reported in the literature (e.g., Nanoscale, 2020, 12, 18067, Adv. Optical Mater. 2021, 2101232, Angew. Chem. Int. Ed. 2025, e202507829)? Or could there be other possible origins? The authors should provide a brief discussion to clarify the origin of this signal.\n4, There appears to be a notable discrepancy between the calculated CD spectrum in Fig. 2c and the experimentally measured CD spectrum in Fig. 2e. The simulated signal is concentrated in the 250-300 nm range with negligible features beyond 300 nm, whereas the experimental CD spectrum shows prominent signals from 300-400 nm. Moreover, the calculated signals in the 250-300 nm range likely originate from the organic ligands rather than from chirality transfer within the perovskite lattice. Therefore, the calculation may not effectively capture the chirality transfer from chiral ligands to the 1D crystal structure of the perovskite. The authors should carefully analyze and discuss these differences.\n5, If feasible, the authors are encouraged to include more details about the computational procedure used to generate the CD spectra shown in Fig. 2c in the Methods section.\n6，According to the authors, the absorption between 550–750 nm arises from a charge-transfer state, which typically has weak oscillator strength. It is thus surprising that this region shows a significant CD signal. The authors are encouraged to explain why such a weak transition would exhibit noticeable chiroptical activity.\n5, Are the observed CD signals in the charge-transfer region dependent on the doping level of F4TCNQ? A short discussion or supporting figure would strengthen the conclusion of chirality transfer.\n6, The authors mention using sample rotation to suppress linear dichroism artifacts in CD measurements. To further exclude the influence of linear dichroism and linear birefringence (LDLB), it is recommended to perform measurements from both front and back sides of the film, as demonstrated in Nat. Commun. 2022, 13, 3259 and Sci. Adv. 2024, 10, eado5942\n7, Have the authors performed control experiments on F4TCNQ-doped achiral perovskite films? Such a comparison would help confirm that the CD activity of the CT state originates from the chiral host.\n8, The justification for using a 290 nm excitation in transient absorption measurements to selectively excite the host material is somewhat unclear. According to Fig. S3, F4TCNQ also shows absorption at 290 nm, and in Figs. S8-S9, F4TCNQ-only films respond to 340 nm excitation. Why would a lower-energy (340 nm) photon excite F4TCNQ while a higher-energy (290 nm) one would not? The authors should clarify this point.\n9, In CD (Fig. 2) and TAS (Fig. 3) measurements, the authors use 10% F4TCNQ-doped perovskite films, while in the XRD measurement (Fig. 3), they use 1% doping. Please clarify the rationale for using different concentrations across measurements. Is it possible that excess F4TCNQ impacts crystallinity beyond the discussed intercalation effects? Additionally, the authors should specify the F4TCNQ concentration used in the CPL photodetector devices.\n10, While the CPL detector performance is introduced through the photocurrent dissymmetry factor (gcurrent), more comprehensive device characterization is encouraged. Including parameters such as responsivity, EQE, or specific detectivity would provide a clearer benchmark of device quality relative to previously reported CPL photodetectors.\n11, The authors report gcurrent values of 0.12-0.18, which are an order of magnitude higher than the corresponding gCD values. Although this amplification is commonly seen in perovskite-based CPL detectors, a brief discussion of possible mechanisms would improve the completeness of the work.\n12, The authors focus on the dependence of on/off ratio on film thickness, but gcurrent may also vary with thickness. It would be helpful to include a discussion on how film thickness affects gcurrent.", "reviewer_2": "The authors introduced a chirality transfer from chiral perovskite to molecular dopant via charge transfer states. By doping F4TCNQ into hybrid organic-inorganic perovskite precursor, the chiral perovskite matrix enhanced their electrical conductivity with an addition of visible light absorption through the emerging charge-transfer electronic states. They validated the phenomena by transient absorption spectroscopy and theory modeling and further integrated the doped chiral perovskite film into photodetectors. However, I think this work is not appropriate for the publication in Nature Communications, but should be considered for an alternative journal. Below are suggestions that might help to improve the paper before it is published.\n1. The chemical composition of the synthesized chiral perovskite single crystals is not clearly defined. While the Methods section refers to the material as (R/S-MP)₂PbI₄, this stoichiometry does not correspond to a typical face-sharing octahedral structure. In the main text, the authors describe the structure as an analogue of ((CH₃)₃S⁺)₄Pb₃Br₁₀, yet the figure provided does not appear to match the referenced structure. Given the central role of structural configuration in interpreting electronic and optical properties, crystallographic analysis should be provided to clarify the material's actual structure.\n2. Circular dichroism (CD) and absorption data are inconsistent across the manuscript. For example, discrepancies are observed between Figure 2f and Supplementary Figures S5–S7. Since chirality transfer and associated optical activity are essential components of the manuscript’s claims, the authors should ensure internal consistency across these datasets and clarify any differences in measurement conditions or sample configurations that might explain the inconsistencies.\n3. The manuscript claims that the crystal structure of the synthesized (R/S)-MP perovskite was obtained via X-ray scattering and subsequently used as the basis for TDDFT calculations. However, no crystallographic data (e.g., CIF files or atomistic coordinates) are provided in either the main text or supplementary information. Without access to this structural data, the TDDFT results presented in the study cannot be independently verified or reproduced. Moreover, in the absence of properly resolved and validated crystal structures, any theoretical modeling — particularly those involving chiroptical properties and charge-transfer excitations — may be based on assumptions that compromise the accuracy of the predictions. I strongly recommend the authors provide the exact structural data used in the simulations or otherwise clarify the basis for their modeling approach.\n4. Theoretical models suggest two possible dopant configurations (intercalation vs substitution), but experimental evidence supporting the favored model (model-2) remains ambiguous. Although GIWAXS and XRD results are presented, the authors do not provide sufficient structural refinement or detailed analysis (e.g., Rietveld fitting) to conclusively support the substitutional doping model. This weakens the central argument regarding the spatial proximity needed for effective chirality and charge transfer.\n5. Transient absorption (TA) spectroscopy suggests the presence of charge transfer states, but the analysis remains primarily qualitative. There is a need for additional spectroscopic characterization (e.g., photoluminescence, EPR, or time-resolved photoluminescence) to validate the assignment of these CT states more conclusively. While control experiments using F4TCNQ alone are included in the supplementary data, quantitative kinetic comparisons between doped and undoped samples should be integrated into the main text for clarity.\n6. The manuscript introduces the concept of charge transfer (CT) states from the beginning and refers to them frequently throughout the main text. However, the CT state is not a common concept in the field of chiral perovskites. It would be helpful to include a simple schematic or a brief explanation. This addition could guide readers who are less familiar with the concept and clarify how the CT state arises and operates in this system.\n7. According to the model-2 simulation, the F4TCNQ dopant substitutes into the perovskite lattice, possibly replacing the R-/S-MP chiral ligands. However, the manuscript does not explain what happens to the original ligands when this structural change occurs. Since the perovskite films were prepared by dissolving single crystals, it isn’t easy to control the composition of the perovskite in the solution. Nevertheless, it would be valuable to explore whether reducing the amount of chiral ligand in the precursor solution (for example, R/S-MP:Pb2+ = 1.8:1 to 1:1) affects the incorporation of the dopant or the formation of CT states. This type of experiment could offer insight into how the dopant interacts with the host lattice at the molecular level.\n8. As the formation of charge-transfer states through F4TCNQ doping is the central theme of the manuscript, it would be appropriate for the device data to directly reflect this effect. However, the main figures do not clearly present a side-by-side comparison of devices with and without F4TCNQ doping. Including such comparisons would make the impact of doping on device performance more evident.\n9. In the CPL sensing measurements, it is unclear how the authors generated right-handed circularly polarized (RCP) light using linear polarizer and quarter-wave plate angles of 45°, 135°, 225°, and 315°, as all four settings are described as producing RCP. The authors are encouraged to clarify how polarization states were defined and verified. Furthermore, it would be helpful to specify which angle was used as the reference in the g-factor calculation. Lastly, Figure 5b and blue colored graph in Figure 5c show noticeably different g values; the origin of this discrepancy should be discussed.\n10. There are some typographical errors\n1) On page 2, “futher” should be corrected to “further”\n2) On page 5, “gracing indicent X-ray scattering pattern”\n3) In the caption of Figure 1: \"perovksites\"\n4) On page 6, “Fig. 2b” should be corrected to “Fig.2c”\n5) In Figure S4, “RMP” should be corrected to “SMP”", "reviewer_3": "Nie et al employed a molecular doping strategy to enhance the electrical conductivity of chiral perovskites and expand their absorption in the visible to IR region. They have successfully introduced the charge transfer states into the chiral perovskites by doping F4TCNQ, which not only enhanced the electrical conductivity of the chiral perovskite but also expanded its absorption range for visible light. The experimental and theoretical calculations demonstrated that these charge transfer states inherited the CD of chiral perovskites, indicating an effective chirality transfer from the host chiral perovskite to the guest F4TCNQ. The existence of these charge transfer states was verified by transient absorption spectroscopy and theoretical modeling. In addition, they integrated these doped chiral perovskites into the circularly polarized photodetector, demonstrating its selective detection ability for circularly polarized light in both the ultraviolet and visible light regions. Overall, this study provides a universal method for optimizing the optoelectronic properties of chiral perovskites, which is very important for the development of chiral perovskite towards real electronic and spintronic device. Therefore, I recommend to accept this work after addressing the below minor issues.\n1. The energy level of F4TCNQ and chiral perovskite together with the CT state should be plotted to clarify the origin of the CT state.\n2. The description about the realization of high-performance metallic nanostructures in the near-infrared band should be cited with reference.\n3. The single-crystal structure R/S-MP was determined to be the Sohncke space group of P21/c (e.g., Fig. 2b). However, P21/c is not a Sohncke space group. The cif file and structure information of R/S-MP should be provided as supplementary information.\n4. The calculated CD spectra of R/S-MP does not match well with the experimental results in Figure 2e. Here the whole crystal is used for CD calculation, or just a small cluster (like Figure 4a-4c) from the crystal?\n5. The latest progress of chiral perovskite should be included (DOI: 10.1021/jacs.4c06822, 10.1038/s41467-025-56394-9).\n6. As shown in Figure 5a, the incidence angle is 45 deg, why normal incidence is not applied? In fact, if the incidence angle is 45 deg, this will introduce the extrinsic chirality.\n7. The authors explained the experimental d-spacing of 13.78 Å and 6.98 Å as a stacking of “two F4TCNQ molecules (d = 7.3 nm).” 7.3 nm = 73 Å, which is more than a 10-fold difference from the experimental value.\n8. Some small errors in the paper that need to be corrected, such as “290nm” in Fig.3.\nI. “Fig. 2b displays the computed CD spectra” This should be Fig. 2c.\nII. There are abbreviation of R-MP, S-MP, RMP, SMP in both the manuscript and supplementary information, which should be consistent. BTW, it is also confused that R/S-MP means the chiral perovskite or chiral cations (Figure 2a)?\nIII. What does (R-MP)2PbI2(OH)2 or (S-MP)2PbI2(OH)2 mean in Figure S1?"}, "author_response": "We sincerely thank all the reviewers for their time and effort in providing insightful and constructive comments, which have significantly enhanced the quality of our manuscript. In revising the manuscript in response to these comments, we have deepened our understanding of this fascinating system. We believe that the revised version now meets the high standards required for publication in Nature Communications. Below, we present a detailed point-by-point response to each reviewer’s comment, followed by the corresponding revisions made to the manuscript. [Author response text truncated for brevity as per instructions to parse the provided text]"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors’ revisions have sufficiently improved the quality of the manuscript. I am satisfied with the changes the authors made, and I believe the paper is suitable for publication in Nature Communications after the following minor issues are addressed.\nComment 1: In the main text, the authors state: “However, its R begins to decline with further increases in thicknesses over 400 nm owing to poor conductivity. In contrast, the R of the doped device continuously increases with thickness and levels off around 700 nm, aided by the improved conductivity.” However, this trend is not supported by Figure 5d. In Figure 5d, both S-MP pristine and S-MP doped devices show that R begins to decline when the thickness exceeds ~800 nm. By contrast, both R-MP pristine and R-MP doped devices show that R continuously increases with thickness up to ~1800 nm. Therefore, the thickness dependence of R appears to be more strongly related to the perovskite chirality (S-MP vs R-MP) rather than doping. Please revise the discussion to accurately reflect Figure 5d.\nComment 2: Closely related to the point above, the manuscript does not explain why the thickness dependence of R differs so much between S-MP and R-MP devices. In particular, it is surprising that the R-MP devices still show increasing R even at ~1800 nm thickness. For 2D perovskites, the out-of-plane carrier transport is usually limited, and such a large effective collection thickness is unexpected. Please provide a reasonable explanation (and supporting evidence where possible) for the strongly different thickness trends between S-MP and R-MP.\nComment 3: The caption of Figure 5 contains an error. It states that panel (e) shows “external quantum efficiency (EQE) plotted as a function of the absorber’s thickness,” but panel (e) actually shows responsivity (R) plotted as a function of the absorber’s thickness. Please correct the caption.\nComment 4: There seems to be a systematic mismatch between the thickness values described in the text and the thickness values shown in Figure 5.In several places, the thickness values in the text appear to be about half of those on the figure axis. For example, on Page 21 the authors write: “In the pristine sample, the gcurr first increases with thickness from 100 nm to 400 nm. After 400 nm, the gcurr starts to decay with higher thickness.” However, in Figure 5f the turning point of gcurr is around ~800 nm. Please carefully check and correct all thickness values in the text, figure axes, and captions to ensure consistency throughout the manuscript.", "reviewer_2": "The manuscript has been thoroughly and rigorously reviewed, and the authors have carefully addressed the reviewer comments with detailed revisions throughout the text. In particular, the clarity, consistency, and scientific rigor of the manuscript have been significantly improved compared to the previous version. The authors’ substantial efforts to conduct multiple additional experiments are clearly reflected in the revised manuscript, strengthening both the reliability and completeness of the study.\nIn recognition of the authors’ diligent revisions and comprehensive responses, I believe that the manuscript is now suitable for publication in Nature Communications.", "reviewer_3": "The authors have addressed my concerns, and now the manuscript can be accepted."}, "author_response": "We sincerely thank all the reviewers for their time and effort in providing insightful and constructive comments, which have significantly enhanced the quality of our manuscript. In revising the manuscript in response to reviewer #1’s comments, we have deepened our understanding of this fascinating system. We believe that the revised version now meets the high standards required for publication in Nature Communications. Below, we present a detailed point-by-point response to each reviewer’s comment, followed by the corresponding revisions made to the manuscript. [Author response text truncated for brevity as per instructions to parse the provided text]"}, {"round": 3, "reviewer_comments": {"reviewer_1": "The authors have satisfactorily addressed all my concerns and questions. Therefore, I consider that the manuscript can now be accepted for publication."}, "author_response": ""}]

Decision letter