Understanding the Mechanism between Antisolvent Dripping and Additive Doping Strategies on the Passivation Effects in Perovskite Solar Cells.

Abstract

Perovskite polycrystalline films contain numerous intrinsic and interfacial defects ascribed to the solution preparation process, which are harmful to both the photovoltaic performance and the stability of perovskite solar cells (PVSCs). Although various passivators have been proved to be promising materials for passivating perovskite films, there is still a lack of deeper understanding of the effectiveness of the different passivation methods. Here, the mechanism between antisolvent dripping and additive doping strategies on the passivation effects in PVSCs is systematically investigated with a nonfullerene small molecule (F8IC). Such a passivated effect of F8IC is realized via coordination interactions between the carbonyl (C═O) and nitrile (C-N) groups of F8IC with Pb2+ ion of MAPbI3. Interestingly, F8IC antisolvent dripping can effectively passivate the surface defects and thus inhibit the nonradiative charge recombination on the upper part of the perovskite layer, whereas F8IC additive doping significantly reduces the surface and bulk defects and produces a compact perovskite film with denser crystal grains, thus facilitating charge transmission and extraction. Therefore, these benefits are translated into significant improvements in the short-circuit current density (Jsc) to 21.86 mA cm-2 and a champion power conversion efficiency of 18.40%. The selection of an optimal passivation strategy should also be considered according to the energy level matching between the passivators and the perovskite. The large energetic disparity is unsuitable for additive doping, whereas it is expected in antisolvent dripping.