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The bandgap of inorganic halide perovskites plays a crucial role in the efficiency of solar cells. Although density functional theory can be used to calculate the bandgap of materials, the method is time-consuming and requires deep knowledge of theoretical calculations, theoretical calculations are frequently constrained by complex electronic correlations and lattice dynamics, resulting in discrepancies between calculated and experimental results. To address this issue, this study employs machine learning to predict the bandgap of inorganic halide perovskites. The XGBoost classifier classifies ABX3-type inorganic halide perovskites into narrow and wide bandgap materials. The study collected a dataset consisting of 447 perovskites and generated material descriptors using the Matminer Python package. The model predicts narrow-bandgap materials with 95% accuracy. Finally, the Shapley analysis revealed that the key factor affecting the bandgap of perovskites is the electronegativity range. As the range of electronegativity increases, so does the possibility of a perovskite with a narrow bandgap. These findings highlight the powerful ability of machine learning to quickly and accurately predict the bandgap of perovskites. [ABSTRACT FROM AUTHOR]

Lewis-base polymers have been widely utilized as additives to act as a template for the perovskite nucleation/crystal growth and passivate the under-coordinated Pb2+ sites. However, it is uncovered in this work that the polymer on the perovskite grain boundaries would significantly hinder the charge transport due to its low conductivity, which brings about free carrier recombination and photocurrent losses. To circumvent this issue while fully exploiting the benefits of polymers in passivating the trap states in perovskite, we incorporate highly conductive multiwall carbon nanotubes (CNTs) with Lewis-base polymers as co-additives in the perovskite film. Functionalizing the CNTs with -COOH group enables a selective hole-extraction and charge transport from perovskite to the hole transporting materials (HTM). By studying the charge transporting and recombination dynamics, we revealed the individual role of the polymer and CNTs in passivating the trap states and facilitating the charge transport, respectively. As a result, the perovskite solar cells (PSCs) with polymer-CNTs composites exhibit an impressive PCE of 21.7% for a small-area device (0.16 cm2) and 20.7% for a large-area device (1.0 cm2). Moreover, due to the superior mechanical flexibility of both polymer and CNTs, the polymer-CNTs composites incorporation in the perovskite film encourages the fabrication of flexible PSCs (f-PSCs) with an impressive PCE of 18.3%, and a strong mechanical durability by retaining 80% of the initial PCE after 1,000 times bending. In addition, we proved that the selection criteria of the polymers can be extended to other long-chain Lewis-base polymers, which opens new possibilities in design and synthesis of inexpensive material for this tactic towards the fabrication of high performance large-area PSCs and f-PSCs. [ABSTRACT FROM AUTHOR]

We fabricated inverted polymer solar cells (PSCs) with the structure of ITO/ZnO NPs/Active layer/MoO3/Ag, in which ZnO NPs act as electron transport layer (ETL), poly{4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b0]-dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophene-4,6-diy (PTB7) as donor and [6,6]-phenyl-C71-butyric-acidmethyl-ester (PC71BM) as accepter. It is found that the temperature employed during the annealing process of ZnO NPs has significant impact on the efficiency of the resulted PSCs. The optimized PSC with ZnO NPs annealed at 150 °C based on PTB7:PC71BM (1:1.5 w/w) exhibited a power-conversion efficiency of 7.37% with open-circuit voltage (Voc) of 0.722 V, short-circuit current density (Jsc) of 15.38 mA cm−2, and fill factor (FF) of 66.4%. The effects of the annealing temperature on photovoltaic performances were further illustrated with transmission spectrum, atomic force microscopy, X-ray diffraction and PL spectra, meanwhile electrical performance were illustrated with conductivity. Our result indicated that the improved efficiency is due to the optimized ETL/active layer interface, the enhanced transparency and electron transport of the ETLs. As its facile preparation process, this kind of ETL is compatible with roll-to-roll manufacturing of larger area flexible PSCs. [ABSTRACT FROM AUTHOR]

High boiling point solvent additive, employed during the solution processing of active layer fabrications, impact the efficiency of bulk heterojunction polymer solar cells (PSC) by influencing the morphological of the active layer. The photovoltaic performances of the PSCs based on the donor of poly{4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]-dithiophene-2,6-diyl-alt-3-fluoro-2-[(2 ethylhexyl)carbonyl] thieno[3,4-b]thiophene-4,6-diy (PTB7) and the acceptor of [6, 6]-phenyl-C71-butyric-acidmethyl-ester (PCBM) was optimized using 5 vol% high-boiling-point solvent additive of 2-Bromonaphthalene (BN). The optimized air-processed PSC based on PTB7:PCBM (1:1.5 w/w) with 5 vol% BN exhibited a power conversion efficiency of 7.01% with open-circuit voltage ( V ) of 0.731 V, short-circuit current density ( J ) of 13.79 mA cm, and fill factor (FF) of 69.46%. The effects of the additive on photovoltaic performances were illustrated with atomic force microscopy and transmission electron microscope measurements. Our results indicate that the improved efficiency is due to the optimized PTB7/PCBM interpenetrating network and the enhanced absorption of the active layer using the BN as solvent additive. [ABSTRACT FROM AUTHOR]

CH3NH3PbI3 perovskite films with full coverage and negligible roughness have been obtained by the two-step sequential thermal evaporation (TSSTE) process, which are further applied to fabricate thin-film transistors (TFTs). To gain the optimal electrical characteristics in our TFTs, the effect of the evaporation amount of PbI2 on the crystallization and thickness of CH3NH3PbI3 films is studied during the process of TSSTE. As a result, we demonstrate a thin-film field-effect transistors possessing a hole field-effect mobility of 3.55 cm2 V− 1 s− 1 as well as on/off ratio greater than 105 with the optimal CH3NH3PbI3 films as the channel layer. Through a further comparative analysis, MoO3 buffer layer is inserted between the perovskite channel layer and the source-drain electrode to improve the contact resistance of TFTs. As an understanding of device mechanism, a fact that insertion of MoO3 buffer layer into the Au/perovskite interface significantly reduced the contact resistance from 705 to 0.2 kΩ cm is unveiled. By inserting MoO3 buffer layer, the hole field-effect mobility of the CH3NH3PbI3 organic-inorganic hybrid TFTs can reach to 7.47 cm2 V− 1 s− 1. [ABSTRACT FROM AUTHOR]