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Abstract The organic–inorganic halide CH 3 NH 3 PbI 3 (MAPbI 3 ) has been the most commonly used light absorber layer of perovskite solar cells (PSCs); however, solution‐processed MAPbI 3 films usually suffer from random crystal orientation and high trap density, resulting in inferior power conversion efficiency (PCE) with open circuit voltage ( V oc ) being typically below 1.2 V for PSC devices. Herein, for the first time an imidazole sulfonate zwitterion, 4‐(1H‐imidazol‐3‐ium‐3‐yl)butane‐1‐sulfonate (IMS), is applied as a bifunctional additive in regular‐structure planar heterojunction PSC devices to regulate the crystal orientation, yielding highly ordered MAPbI 3 film and passivating the trap states of the film. Such a dual effect of IMS is fulfilled via coordination interactions between the sulfonate moiety of IMS with the Pb2 + ion and the electrostatic interaction between the imidazole of IMS with the I – ion of MAPbI 3 . As a result, under a optimized IMS doping ratio of 0.5 wt%, the PSC device exhibits a significant increase in PCE from 18.77% to 20.84%, with suppressed current–voltage hysteresis and promoted ambient stability. Moreover, a high V oc of 1.208 V is achieved under a higher IMS doping ratio of 1.2 wt%, which is the highest V oc for regular‐structure MAPbI 3 planar PSC devices based on TiO 2 electron transport layer.
Zhou et al. (Thu,) studied this question.