Manipulating the Migration of Iodine Ions via Reverse‐Biasing for Boosting Photovoltaic Performance of Perovskite Solar Cells

Perovskite solar cells (PSCs) are being developed rapidly and exhibit greatly potential commercialization. Herein, it is found that the device performance can be improved by manipulating the migration of iodine ions via reverse‐biasing, for example, at −0.4 V for 3 min in dark. Characterizations suggest that reverse bias can increase the charge recombination resistance, improve carrier transport, and enhance built‐in electric field. Iodine ions including iodine interstitials in perovskites are confirmed to migrate and accumulate at the SnO(2)/perovskite interface under reverse‐basing, which fill iodine vacancies at the interface and interact with SnO(2). First‐principles calculations suggest that the SnO(2)/perovskite interface with less iodine vacancies has a stronger interaction and higher charge transfer, leading to larger built‐in electric field and improved charge transport. Iodine ions that may pass through the SnO(2)/perovskite interface are also confirmed to be able to interact with Sn(4+) and passivate oxygen vacancies on the surface of SnO(2). Consequently, an efficiency of 23.48% with the open‐circuit voltage (V (oc)) of 1.16 V is achieved for PSCs with reverse‐biasing, as compared with the initial efficiency of 22.13% with a V (oc) of 1.10 V. These results are of great significance to reveal the physics mechanism of PSCs under electric field.