Preparation of CH_3NH_3PbI_3 thin films for solar cells via Vapor Transfer Method

Organometal halide perovskite based solar cells have emerged as one of the most promising candidates for low-cost and high-efficiency solar cell technologies. Here a Vapor Transfer Method （VTM） is used to fabricate high quality perovskite thin films in a balanced vacuum capsule. By adjusting the reaction tem- perature, CH_3NHl_3 saturated vapor which then reacts with Pbl_2 films can be controlled and the formation process of CH_3NH_3Pbl_3 perovskite films can be further influenced. Prepared perovskite films which ex- hibit pure phase, smooth surface and high crystallinity are assembled into planar heterojunction inverted solar cells. The whole fabrication process of solar cell devices is organic solution free. Finally, the cham- pion cell achieved power conversion efficiency （PCE） of 13.08% with negligible current-voltage hysteresis under fully open-air conditions. The photovoltaic performance could be further enhanced by optimizing perovskite composition and the device structure.

Doping Electron Transporting Layer:An Effective Method to Enhance J_(SC)of All-Inorganic Perovskite Solar Cells

All-inorganic metal-halide CsPbBr_(3)perovskite has emerged as an attractive photovoltaic material for its outstanding environmental stability.However,due to the wide bandgap,the performance of CsPbBr_(3)perovskite solar cells(PSCs)is limited,especially for the short-circuit current density(J_(SC)).In this issue of Energy&Environmental Materials,Guo et al.employed Nb-doped SnO_(2)as electron transporting layers(ETLs),which could greatly improve the J_(SC)of the PSCs based on all-inorganic CsPbBr_(3).

Subtle Alignment of Organic Semiconductors at the Donor/Acceptor Heterojunction Facilitates the Photoelectric Conversion Process

The aligned molecular packing structure is vital to the anisotropic charge transport in conjugated polymer and small molecule thin films.However,how this molecular packing motif influences the photoelectric conversion process at the donor/acceptor heterojunction is still mysterious.Herein,we employed a PM6/Y6 bilayer model to investigate the long-range alignment of molecular packing induced photoelectric conversion process.Both PM6 and Y6 layers were properly controlled to exhibit the uniaxially oriented molecular packing compared to their as-cast counterparts,as revealed by the polarized absorption spectra and transmission electron microscopy.After analyzing the photovoltaic performance of bilayer devices,the smaller energy loss,lower energetic disorder,and longer charge carrier lifetime can be observed in the bilayer devices with aligned Y6 molecules,which contribute to a higher power conversion efficiency(PCE)than the as-cast devices.While the molecular packing structure of PM6 layer exhibited negligible influence on the device performance,probably resulting from the intrinsic semicrystalline nature of PM6 molecules.Our results indicate that the alignment of small molecular acceptor at the donor/acceptor interfaces should be a powerful strategy to facilitate the photoelectric conversion process,which will definitely pave the way to highly efficient bulk heterojunction photovoltaic device.

Solution sequential deposited organic photovoltaics:From morphology control to large-area modules

Organic optoelectronic materials enable cutting-edge,low-cost organic photodiodes,including organic solar cells(OSCs)for energy conversion and organic photodetectors(OPDs)for image sensors.The bulk heterojunction(BHJ)structure,derived by blending donor and acceptor materials in a single solution,has dominated in the construction of active layer,but its morphological evolution during film formation poses a great challenge for obtaining an ideal nanoscale morphology to maximize exciton dissociation and minimize nongeminate recom-bination.Solution sequential deposition(SSD)can deliver favorable p–i–n vertical component distribution with abundant donor/acceptor interfaces and relatively neat donor and acceptor phases near electrodes,making it highly promising for excellent device performance and long-term stability.Focusing on the p–i–n structure,this review provides a systematic retrospect on regulating this morphology in SSD by summarizing solvent selection and additive strategies.These methods have been successfully implemented to achieve well-defined morphology in ternary OSCs,all-polymer solar cells,and OPDs.To provide a practical perspective,comparative studies of device stability with BHJ and SSD film are also discussed,and we review influential progress in blade-coating techniques and large-area modules to shed light on industrial production.Finally,challenging issues are out-lined for further research toward eventual commercialization.

Over 16% efficiency all-polymer solar cells by sequential deposition

All-polymer solar cells(all-PSCs) have received extensive attention due to their excellent mechanical robustness and performance stability. However, the power conversion efficiency(PCE) of all-PSCs still lags behind those of organic solar cells(OSCs)based on non-fullerene small molecule acceptors. Herein, we report highly efficient all-PSCs via sequential deposition(SD) with donor and acceptor layers coated sequentially to optimize the film microstructure. Compared with the bulk heterojunction(BHJ)all-PSCs, an optimized morphology with vertical component distribution was achieved for the SD-processed all-PSCs due to the synergistic effect of swelling of polymer films and using additive. Such strategy involves using chlorobenzene as the first layer processing-solvent for polymer donor, chloroform as the second processing-solvent for polymer acceptor with trace 1-chloronaphthalene, efficiently promoting exciton dissociation and charge extraction and reducing trap-assisted recombination.Consequently, over 16% all-PSCs fabricated via SD method was realized for the first time, which is much higher than that(15.2%) of its BHJ counterpart and also among the highest PCEs in all-PSCs. We have further demonstrated the generality of this approach in various all-polymer systems. This work indicates that the SD method can yield excellent all-PSCs and provides a facile approach to fabricating high-performance all-PSCs.

有机和钙钛矿太阳能电池的界面调控（英文）

有机太阳能电池具有柔性、廉价、质轻等优势,多年来一直受到研究人员的大量关注,光电转换效率已经达到10%以上.特别是最近几年,基于有机-无机杂化的钙钛矿太阳能电池发展迅猛,短短几年内,光电转换效率突破了20%.界面对有机和钙钛矿太阳能电池的光电转换效率和稳定性具有举足轻重的作用.因此,研究人员聚焦有机和钙钛矿太阳能电池的界面材料、界面修饰、界面工程等开展了深入研究,并取得了诸多进展.本文主要基于作者课题组多年来在有机和钙钛矿太阳能电池的界面研究所取得的初步进展进行了总结,并对界面材料的发展方向进行了展望,期望满足未来基于印刷技术制备高效率、大面积、柔性有机和钙钛矿太阳能电池的需要.