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solution processes and have been proved to have similar optoelectronic properties with their organic counterparts. [24][25][26] So far, CsPbX 3 perovskites have been widely studied as alternative light absorbers in PSCs and considerable efforts are being made to improve device performance. [27][28][29][30][31][32][33][34] Among these efforts, organic molecular engineering in CsPbX 3 perovskites are the most straightforward method to improve device stability and PCE. [31,32] Since CsPbX 3 PSCs were first reported in 2015, great progress has been made on organic molecular engineering and over 19% PCE has been achieved. [35][36][37][38][39] In this review, we systematically reviewed and discussed the current development of organic molecular engineering in inorganic CsPbX 3 PSCs. First, structure evolution induced by organic molecular engineering was demonstrated. Then, the progresses on the inorganic CsPbX 3 PSCs will be reviewed and discussed in detail according to different molecule function (alloying in perovskite structures, as sacrificial agents, forming 2D structures, and modifying surfaces and interfaces). Finally, the current issues of molecular engineering will be pointed out and future directions will be highlighted.

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Herein, high-temperature (over 200 C) perovskite solar cells (PSCs) are fabricated and studied for the first time. Inorganic CsPbI 2 Br perovskite is used as absorber and carbon nanotubes (CNTs) are directly used as the hole extraction electrode. Such device retains over 80% of its initial power conversion efficiency (PCE) after heating at 200 C for 45 h, enabling its operation at high temperatures. By recording reverse and forward J-V curves at different temperatures (25-220 C), temperature coefficients of photovoltaic parameters are obtained. Compared with conventional high-temperature solar cells (Si, CuInGaSe, and GaAs), CsPbI 2 Br devices show superior V OC and FF temperature coefficients but inferior J SC temperature coefficients. As a result, PCE temperature coefficients of CsPbI 2 Br devices are superior over Si and CuInGaSe solar cells, and are comparable with those of GaAs solar cells. Meanwhile, the mitigation of charge accumulation at elevated temperatures results in a gradual decrease in J-V hysteresis. Therefore, this study may expand the application of PSCs into high-temperature fields, such as space exploration.

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