All-inorganic CsPbX3perovskites have significant potential for applications in the photovoltaic field. However, during their preparation, the slow evaporation rate of the precursor solution limits the extent of solution supersaturation, leading to porous perovskite films that substantially impair device performance. Anti-solvent engineering, which introduces a secondary solvent to modulate the crystallization process, is a well established technique in perovskite photovoltaic research. This study systematically examines the effects of four different anti-solvents on perovskite films and corresponding devices. It also investigates the optimal dipping-time of (trifluoromethyl)benzene as an anti-solvent, as well as the impact of varying amounts of anti-solvent additive perfluorinated acid. The optimized devices achieved a maximum power conversion efficiency of 12.68%.
Weizhi Zhang,Taiyang Zhang,Lixia Qin,Shi-Zhao Kang,Yixin Zhao,Xiangqing Li
The purity of PbI 2 plays a critical role in determining the performance, stability, and reproducibility of perovskite solar cells (PSCs). However, the cost of high-purity PbI 2 is much higher than that of low-purity, and even the expensive high-purity PbI 2 suffers from batch variance issues. Although several purification methods have been developed, the straightforward and rapid purification of PbI 2 remains a challenge. The solar cell efficiency achieved by previous direct purification of PbI 2 is much lower than the state-of-the-art value. Therefore, people still doubt whether the low-purity PbI 2 is eligible for the fabrication of efficient solar cells even after purification. Herein, we report an anti-solvent engineering strategy for the rapid and facile purification of low-purity PbI 2 , which allows us to efficiently eliminate both the insoluble and soluble impurities. Eventually, the formamidinium-cesium (FA 0.95 Cs 0.05 PbI 3 ) PSCs made from directly purified PbI 2 show much enhanced performance and reproducibility. A champion power conversion efficiency of 23.91% is realized, which is the highest value ever reported for PSCs made from purified low-purity PbI 2 . The in-depth PbI 2 purification mechanism is further discussed from the perspective of solvent-coordination and solvent–solvent interactions by combining the donor number (D N ) value of solvents and Hansen solution parameters. The results reveal that the weaker interaction between PbI 2 and solvent, together with the stronger interaction between solvent and anti-solvent, is crucial for achieving successful purification. This study not only provides a simple and rapid method for the purification of PbI 2 but also enhances our understanding of the selective crystallization of PbI 2 and perovskite by elucidating the solvate and de-solvation processes of PbI 2 within the perovskite precursor.
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