Targeted Therapy for Interfacial Engineering Toward Stable and Efficient Perovskite Solar Cells.

The poor long-term stability of organic-inorganic hybrid halide perovskite solar cells (pero-SCs) remains a big challenge for their commercialization. Although strategies such as encapsulation, doping, and passivation have been reported, there remains a lack of understanding of the water resistance and thermal stability of pero-SCs. A fullerene derivative, [6,6]-phenyl-C -butyric acid-N,N-dimethyl-3-(2-thienyl)propanam ester (PCBB-S-N) containing a functional sulfur atom and C is synthesized and employed as electron transporting layer (ETL)/intermediary layer to targetedly heal the multitype defects in pero-SCs or assist the growth of ETL, such as [6,6]-phenyl-C -butyric acid methyl ester (PCBM), in planar p-i-n pero-SCs. The repaired pero-SCs can not only dramatically improve their power conversion efficiencies, but also address stability issues under moisture and high temperature. The corresponding mechanism of PCBB-S-N with targeted therapy effect in a device is systematically investigated by both experiments and theoretical calculation. This work demonstrates that the proposed fullerene derivative with finely tuned chemical structure can be a promising ETL candidate or intermediary to approach stable and efficient planar p-i-n pero-SCs.