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Lead bromide perovskite solar cells (PSCs) have attracted increasing interest partly because of the high open-circuit voltage that has been obtained. Here, we present a simple way to prepare PSCs based on formamidinium lead tribromide, FAPbBr(3), by adding methylammonium chloride and methylammonium bromide into the precursor solution. With this method, high-quality and pin-hole free perovskite films with large crystal sizes were prepared. These additives result in a power conversion efficiency (PCE) of 7.9%, almost free of hysteresis, for a device on a rigid glass substrate. The first flexible lead bromide PSC is also prepared in this work and the flexible PSC exhibited a high PCE of 5.0%.

FAPbBr3 perovskite solar cells (PSCs) have attracted tremendous interest in recent years due to the high open circuit voltage and good stability. Commonly a step method is used to prepare the FAPbBr3 perovskite film. Here a mixed solvent approach for the second step is introduced. Formamidinium bromide (FABr) in 2-propanol (IPA)and Methanol (MeOH) mixture was applied in the second step, which resulted in favorable properties such as suitable solubility, high-quality crystallization, large grainsize, improved charge extraction properties and suppressed non-radiative recombination processes, and further enhance the power conversion efficiency (PCE) from 4.06% to 7.87%. As previously reported, methylammonium chloride (MACl) can help to improve the morphology and crystallinity of perovskite. To further prove the versatility of such a mixed solvent strategy and enhance the photovoltage performance,a small amount of MACl was added to the FABr solution with mixed solvents, and a high PCE of 9.23% was achieved under ambient conditions. 

Lead bromide perovskite with high bandgap and good stability has aroused broad interest for utilization in perovskite solar cells (PSCs) with high photovoltage, especially as a candidate for the front cell of tandem solar cells. However, the efficiency of lead bromide PSCs is still much lower than the standard lead iodide PSCs, and the defects in the perovskite are one of the main limiting factors hindering device performance. The construction of a 2D/3D perovskite interface is an effective way to passivate the interfacial defects and achieve efficient and stable PSCs. Herein, a facile and effective phenethylammonium bromide (PEABr) treatment method was applied to build a 2D/3D perovskite interface in FAPbBr(3) solar cells. An ultrathin layer of 2D PEA(2)PbBr(4) perovskite was successfully fabricated on the surface of 3D FAPbBr(3) perovskite by depositing the PEABr solution on the 3D perovskite films. The 2D perovskite layer significantly passivated the interfacial defects, leading to enhancement of power conversion efficiency from 7.7% to 9.4% and fill factor from 67.6% to 77.6%. Moreover, the hydrophobic alkyl chain in the PEA cation improved the moisture tolerance of the perovskite and significantly increases the solar cell stability. Additionally, the PEABr treatment strategy was successfully utilized for preparing semitransparent 2D/3D FAPbBr(3) perovskite solar cells.

Dopant-free organic hole transport materials (HTMs) remain highly desirable for stable and efficient ni-p perovskite solar cells but are rarely applied in formamidinium lead-bromide (FAPbBr₃) underambient processing. Herein, we compare four dopant-free HTMs on FAPbBr₃- perovskite solar cells (FAPbBr₃-PSCs) according to their structure-property relationship. Among these, P3HT presents higher hole mobility, lower interface trap density, and lower nonradiative recombination, resulting in superior charge extraction and transport. The optimized device utilizing dopant-free P3HT shows a high open circuit voltage of 1.47 V and a champion power conversion efficiency (PCE) of 9.38% with greatly improved operational stability, making it among the highest performance in FAPbBr₃-PSCs based ondopant-free HTMs. Also, to further improve the stability of P3HT- FAPbBr₃ solar cells, the lower cost Carbon electrode was applied to replace the Au, and the resultant carbon-PSCs presented an impressive PCE of 8.9% with a high voltage of 1.44 V. It also keeps excellent stability that almost no degradation nearly one year. 

Despite considerable research efforts on photoelectrochemical (PEC) water splitting over the past few decades, its practical application is still impeded by the lack of efficient, stable, and scalable photoelectrodes. Herein, we demonstrate the facile fabrication of a metal-halide perovskite-based photoanode for PEC water oxidation. A hole transport material-free and precious metal-free FAPbBr₃ photovoltaic (PV) device is fabricated for the first time to examine the charge separation performance of the FAPbBr₃ absorber. With a planar structure using mesoporous carbon as a hole-conducting layer, the device achieved a solar-to-electrical power conversion efficiency of 9.2% and a V_oc of 1.4 V. The solar cell architecture is successfully applied to build a monolithic photoanode with the FAPbBr₃ absorber, carbon/graphite conductive protection layer, and NiFe catalyst layers for direct photo-driven water oxidation. With suitable energy band alignment and minimal contact loss, the photoanode delivers an ultralow onset potential below 0 V versus a reversible hydrogen electrode and a high applied bias photon-to-current efficiency of 8.5%. Stable operation exceeding 100 h under constant solar illumination is successfully reached by the application of UV filter protection. A detailed photothermal investigation confirms that the photothermal effect can improve the overall performance of the perovskite photoanode. The results in this report are of great significance in guiding the further development of PV material-based photoelectrodes for solar fuel applications.