Query: Bi2OS2

title: Interlayer coupling prolonged the photogenerated carrier lifetime of few layered Bi2OS2 semiconductors.
abstract: Layered semiconductors with broad photoabsorption, a long carrier lifetime and high carrier mobility are of crucial importance for high performance optoelectronic and photovoltaic devices; however it is hard to satisfy these requirements simultaneously in a system due to the opposite dependence on the layer thickness. Herein, by means of ab initio time domain nonadiabatic molecular dynamic simulations, we find a new mechanism in Bi2OS2 nanosheets inducing an anomalous layer dependent property of carrier lifetimes, which makes the few layered Bi2OS2 a possible system for fulfilling the above requirements concurrently. It is revealed that the interlayer dipole dipole interaction in few layered Bi2OS2 effectively breaks the two fold degenerate orbitals of [BiS2] layers, which not only cuts down the overlap of the electron and hole wave functions, but also accelerates the electron decoherence process. This significantly suppresses the electron hole recombination and prolongs the photogenerated carrier lifetime of few layered Bi2OS2. The mechanism unveiled here paves a possible way for developing advanced optoelectronic and photovoltaic devices through engineering interlayer dipole dipole coupling.

title: Enhanced carrier mobility and power conversion efficiency of organic solar cells by adding 2D Bi2OS2
abstract: Although polymer solar cells (PSCs) have many advantages, they have obtained great progress in the two decades, the low charge carrier mobility still restricts performance progress of PSCs. Two dimensional (2D) Bi based semiconductor nanomaterial (Bi2OS2) can be a potential material for improving the charge carrier mobility in the active layer of PSCs, because it exhibits a high carrier mobility, suitable band gap, wide absorption range, and good stability. In this work, we synthesize the 2D Bi2OS2 nanomaterial and incorporate it into active layer of PSCs as a third component for the first time. By introduction 1 wt% 2D Bi2OS2 nanomaterial into the PSCs, the power conversion efficiency (PCE) of PSCs can be obviously improved by more than 17% comparison with binary PSCs (from 10.51% to 12.31% The enhancement of PCE is mainly due to the improving of charge transport, surface morphology, and crystallization of active layer. It is worth noting that the 2D Bi2OS2 play the role of the heterogeneous nucleation in the active layer, resulting in the enhanced crystallization of PBDB T and ITIC. These results not only provide a way to improve the performance of PSCs, but also show that the 2D Bi2OS2 nanomaterial has great potential application in the PSCs.

title: Correction: Interlayer coupling prolonged the photogenerated carrier lifetime of few layered Bi2OS2 semiconductors.
abstract: Correction for 'Interlayer coupling prolonged the photogenerated carrier lifetime of few layered Bi2OS2 semiconductors' by Xianghong Niu et al. Nanoscale, 2020, 12, 6057 6063, DOI: 10.1039/

title: Surface modification on nanoripple like ZnO nanorod arrays using two dimensional (2D) Bi2OS2 to fabricate high performance inverted polymer solar cells
abstract: In this paper, three dimensional (3D) nanoripple like ZnO nanorod arrays (R ZnO NRAs) are successfully fabricated and modified by two dimensional (2D) Bi2OS2 material, and inverted polymer solar cells (IPSCs) with R ZnO modified by Bi2OS2 as electron transmission layer (ETL) are fabricated for the first time. The results show that the surface morphologies of R ZnO NRAs can be controlled by adjusting the concentration of the modified 2D Bi2OS2 solution. Bi2OS2 modification can not only suppress the surface defects of R ZnO NRAs, reduce the recombination of photogenerated charges, but also increase crystallinity of the active layer, resulting in effective electron collection. And thus, the performance of IPSCs is obviously improved. The power conversion efficiency (PCE) of PTB7: PCBM based PSCs with R ZnO NRAs modified by 2% Bi2O2S as ETL is considerably raised to 7.31% from 5.51% More interestingly, Bi2OS2 modification enhances IPSCs stability to remain 80.9% of their initial PCE after 80 days, yet IPSCs with pristine R ZnO NRAs remain only 47.4% of their initial PCE. Moreover, this approach can also successfully improve the performance of another IPSC composed of PBDB T: ITIC blends. The PCE of the device based on 2% Bi2OS2 modified R ZnO NRAs is improved to 9.94% from 8.03% of the reference device without Bi2OS2 modification. This work not only provides an effective mean of surface modification of R ZnO NRAs, but also shows the Bi2OS2 material has potential application in PSCs.

title: Two dimensional Bi2OS2 doping improves the performance and stability of perovskite solar cells
abstract: Additive engineering has been proved to be an effective method to increase the performance of perovskite solar cells (PVSCs) by increasing the quality of the perovskite thin film. Two dimensional (2D) Bi2OS2 nanomaterial is an excellence optoelectronic material because of its tunable direct band gap, ultra high charge mobility, wide absorption range and high absorption coefficient. In this work, 2D Bi2OS2 nanosheets are synthesized and introduced as additives into the perovskite precursor solution to adjust the film formation process for the first time. Serving as heterogeneous nucleation site, 2D Bi2OS2 can reduce the nucleation barrier and assist the formation of highly crystalline and crystal orientation along the (1 1 0) plane perovskite thin film, which is beneficial to improve the mobility and lifetime of charge carriers. Besides, X ray photoelectron spectroscopy (XPS) measurement reveals that 2D Bi2OS2 nanosheets can interact with Pb2+ within the perovskite through Pb S bond, thus suppressing the uncoordinated Pb2+ ions trap states. Scanning electron microscope (SEM) demonstrates 2D Bi2OS2 nanosheets can fill up the pin holes and grain boundaries on the perovskite film surface. Ultraviolet photoelectron spectroscopy (UPS) measurement indicates that the valence band (VB) of optimized perovskite film is 0.28 eV upshifted closer to the highest occupied molecular orbital (HOMO) of the hole transport layer (HTL) which accelerates the charge transportation at perovskite/HTL interface. Consequently, the average power conversion efficiency (PCE) of 18.96% (highest PCE of 19.89% is achieved upon incorporating 2D Bi2OS2 nanosheets with an optimized concentration of 0.02 mg/ml into MAPbI3 precursor solution, which is greatly improved compared to the average PCE of 15.71% for the control devices (highest PCE of 16.77% Besides, the lifetime of optimized PVSCs is also prolonged due to the less defect states and better perovskite film quality. This work not only provides a facile method to increase the PCE and stability of PVSCs, but also reveals 2D Bi2OS2 material has potential applications in PVSCs.

title: Bi2OS2: a direct gap two dimensional semiconductor with high carrier mobility and surface electron states
abstract: Two dimensional (2D) semiconductors with desirable band gaps and high carrier mobility are highly sought after for future application in nanoelectronics. Herein, by means of first principles calculations, we predict that a new 2D material, namely a Bi2OS2 nanosheet, possesses not only a tunable direct band gap, but also ultra high electron mobility (up to 26 570 cm2 V 1 s 1) More interestingly, an anomalous layer dependent band gap is revealed, derived from the synergetic effect of the quantum confinement and intrinsic surface electron states. 2D Bi2OS2 also exhibits excellent absorption over the entire solar spectrum and the absorption coefficient is comparable to that of inorganic organic hybrid perovskite solar cells. Moreover, the Bi2OS2 monolayer maintains good structural integrity up to 1000 K and has a relatively small exfoliation energy from its layered bulk. The excellent electronic and optical properties, together with high stability and great experimental possibility, render 2D Bi2OS2 a promising material for future nanoelectronic and optoelectronic applications.

title: Structures and optical absorption of Bi2OS2 and LaOBiS2
abstract: The band gaps of isostructural Bi 2 OS 2 and LaOBiS 2 were examined using optical absorption and discussed with the band structures calculated based on the crystal structures determined using synchrotron X ray diffraction. The Bi 6p and S 3p orbitals in the Bi S plane were computationally predicted to constitute the bands near the Fermi level. The optical reflectance spectra of Bi 2 OS 2 and LaOBiS 2 showed optical band gaps of ~1.0 eV, which were close to the computationally calculated direct band gaps of ~0.8 eV. Our results show that Bi 2 OS 2 and LaOBiS 2 are semiconductors containing direct band gaps of 0.8 1.0 eV, and they are suggested to be candidates for optoelectronic materials in the near infrared region without highly toxic elements.

title: Structures and Optical Properties of Bi2OS2 and LaOBiS2
abstract: The band gaps of isostructural Bi2OS2 and LaOBiS2 were examined using optical absorption and discussed with the band structures calculated based on the crystal structures determined using synchrotron X ray diffraction. The Bi 6p and S 3p orbitals in the Bi S plane were computationally predicted to constitute the bands near the Fermi level. The optical reflectance spectra of Bi2OS2 and LaOBiS2 showed optical band gaps of ca. 1.0 eV, which were close to the computationally calculated direct band gaps of ca. 0.8 eV. Our results show that Bi2OS2 and LaOBiS2 are semiconductors containing direct band gaps of 0.8 1.0 eV, and they are suggested to be candidates for optoelectronic materials in the near infrared region without highly toxic elements.

title: First principles study on the electron and phonon transport properties of layered Bi2OX2 (X S, Se)
abstract: The electron and phonon transport properties of layered bismuth oxychalcogenides Bi2OX2 (X S, Se) are studied by combining density functional theory calculation with the Boltzmann transport theory. It is found that Bi2OS2 and Bi2OSe2 are semiconductors with direct bandgaps of 0.86 eV and 0.63 eV, respectively. A large Seebeck coefficient is found in both p and n doped Bi2OX2 (X S, Se) at 300 K together with their low phonon thermal conductivity (kph) Through a detailed analysis of the phonon dispersion relation, relaxation time, and joint density of states, we find that the low frequency modes contribute dominantly to kph than the high frequency modes. Owing to the high Seebeck coefficient and the low kph, the largest figure of merit (ZT) value can reach 0.5 for the Bi2OX2. The results are useful for further tuning the thermoelectric properties of Bi2OX2 (X S, Se)

title: Optoelectronic and Thermoelectric Properties of Bi2OX2 (X S, Se, Te) for Solar Cells and Thermoelectric Devices
abstract: We have explored the optoelectronic structure and related thermoelectric properties of Bi2OX2 (X S, Se, Te) using density functional theory and spin orbit coupling (SOC) We report herein calculations of the bandgap of these bismuth sulfides/oxysulfides to participate in the recent debate regarding such values. The generalized gradient approximation calculations corrected using the SOC scheme estimated bandgaps of 0.950 eV, 0.635 eV, and 0.441 eV for Bi2OS2, Bi2OSe2, and Bi2OTe2, respectively, in close agreement with experimental results and showing better accuracy compared with available theoretical calculations. This bandgap range shows the potential use of Bi2OX2 for solar cell applications. Hence, we derived their optical and thermoelectric properties. Similarly to one of the parent materials, Bi2S3, a semiconductor with special photovoltaic and thermoelectric properties, the present derivatives Bi2OX2 show promising characteristics for exploration in the near future for use in solar cells and thermoelectric devices.