Modulation of Perovskite Grain Boundaries by Electron Donor-Acceptor Zwitterions R , R -Diphenylamino-phenyl-pyridinium-(CH 2 ) n -sulfonates: All-Round Improvement on the Solar Cell Performance.

Inverted perovskite solar cells (PSCs) have attracted intense attention because of their insignificant hysteresis and low-temperature fabrication process. However, the efficiencies of inverted PSCs are still inferior to those of commercialized silicon solar cells. Also, the poor stability of PSCs is one of the major impedances to commercialization. Herein, we rationally designed and synthesized a new series of electron donor ( R , R -diphenylamino) and acceptor (pyridimium-(CH 2 ) n -sulfonates) zwitterions as a boundary modulator and systematically investigated their associated interface properties. Comprehensive physical and optoelectronic studies verify that these zwitterions provide a four-in-one functionality: balancing charge carrier transport, suppressing less-coordinated Pb 2+ defects, enhancing moisture resistance, and reducing ion migration. Although each functionality may have been reported by specific passivating molecules, a strategy that simultaneously regulates the charge-transfer balance and three other functionalities has not yet been developed. The results are to make an omnidirectional improvement of PSCs. Among all zwitterions, 4-(4-(4-(di-(4-methoxylphenyl)amino)phenyl)propane-1-ium-1-yl)butane-1-sulfonate (OMeZC3) optimizes the balance hole/electron mobility ratio of perovskite to 0.91, and the corresponding PSCs demonstrate a high power conversion efficiency (PCE) of up to 23.15% free from hysteresis, standing out as one of the champion PSCs with an inverted structure. Importantly, the OMeZC3-modified PSC exhibits excellent long-term stability, maintaining almost its initial PCE after being stored at 80% relative humidity for 35 days.