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The organic-inorganic lead halide perovskite layer is a crucial factor for the high performance perovskite solar cell (PSC). We introduce CH3NH3Br in the precursor solution to prepare CH3NH3PbI3−xBrx hybrid perovskite, and an uniform perovskite layer with improved crystallinity and apparent grain contour is obtained, resulting in the significant improvement of photovoltaic performance of PSCs. The effects of CH3NH3Br on the perovskite morphology, crystallinity, absorption property, charge carrier dynamics and device characteristics are discussed, and the improvement of open circuit voltage of the device depended on Br doping is confirmed. Based on above, the device based on CH3NH3PbI2.86Br0.14 exhibits a champion power conversion efficiency (PCE) of 18.02%. This study represents an efficient method for high-performance perovskite solar cell by modulating CH3NH3PbI3−xBrx film.

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Passivating defects to suppress recombination is a valid tactic to improve the performance of third-generation perovskite-based solar cells. Pb0 is the primary defect in Pb-based perovskites. Here, tris­(pentafluorophenyl)­borane is inserted between the perovskite and spiro-OMeTAD layer in SnO2-based planar perovskite solar cells. The incorporation of tris­(pentafluorophenyl)­borane can effectively passivate Pb0 defects, decreasing recombination at the surface of the perovskite film. Additionally, the modification with tris­(pentafluorophenyl)­borane decreases the grain boundaries quantity in the perovskite film, enhancing the transportation capability of carriers. The resulting perovskite solar cell gets a high efficiency of 21.42%. While the reference device without tris­(pentafluorophenyl)­borane treatment acquires an efficiency of 19.07%. More importantly, the stability tests manifest that incorporating tris­(pentafluorophenyl)­borane in perovskite solar cells is conducive to the stability of the device.

Tin oxide (SnO2), as electron transport material to substitute titanium oxide (TiO2) in perovskite solar cells (PSCs), has aroused wide interests. However, the performance of the PSCs based on SnO2 is still hard to compete with the TiO2-based devices. Herein, a novel strategy is designed to enhance the photovoltaic performance and long-term stability of PSCs by integrating rare-earth ions Ln3+ (Sc3+, Y3+, La3+) with SnO2 nanospheres as mesoporous scaffold. The doping of Ln promotes the formation of dense and large-sized perovskite crystals, which facilitate interfacial contact of electron transport layer/perovskite layer and improve charge transport dynamics. Ln dopant optimizes the energy level of perovskite layer, reduces the charge transport resistance, and mitigates the trap state density. As a result, the optimized mesoporous PSC achieves a champion power conversion efficiency (PCE) of 20.63% without hysteresis, while the undoped PSC obtains an efficiency of 19.01%. The investigation demonstrates that the rare-earth doping is low-cost and effective method to improve the photovoltaic performance of SnO2-based PSCs.

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