Organic halide salt passivation is considered to be an essential strategy to reduce defects in state-of-the-art perovskite solar cells (PSCs). This strategy, however, suffers from the inevitable formation of in-plane favored two-dimensional (2D) perovskite layers with impaired charge transport, especially under thermal conditions, impeding photovoltaic performance and device scale-up. To overcome this limitation, we studied the energy barrier of 2D perovskite formation from ortho-, meta- and para-isomers of (phenylene)di(ethylammonium) iodide (PDEAI2) that were designed for tailored defect passivation. Treatment with the most sterically hindered ortho-isomer not only prevents the formation of surficial 2D perovskite film, even at elevated temperatures, but also maximizes the passivation effect on both shallow- and deep-level defects. The ensuing PSCs achieve an efficiency of 23.9% with long-term operational stability (over 1000 h). Importantly, a record efficiency of 21.4% for the perovskite module with an active area of 26 cm2 was achieved.

Organic halide salt passivation is considered to be an essential strategy to reduce defects in state-of-the-art perovskite solar cells (PSCs). This strategy, however, suffers from the inevitable formation of in-plane favored two-dimensional (2D) perovskite layers with impaired charge transport, especially under thermal conditions, impeding photovoltaic performance and device scale-up. To overcome this limitation, we studied the energy barrier of 2D perovskite formation from ortho-, meta- and para-isomers of (phenylene)di(ethylammonium) iodide (PDEAI2) that were designed for tailored defect passivation. Treatment with the most sterically hindered ortho-isomer not only prevents the formation of surficial 2D perovskite film, even at elevated temperatures, but also maximizes the passivation effect on both shallow- and deep-level defects. The ensuing PSCs achieve an efficiency of 23.9% with long-term operational stability (over 1000 hours). Importantly, a record efficiency of 21.4% for the perovskite module with an active area of 26 cm2 was achieved.

The time‐dependent behavior of perovskite devices is one of the limiting factors for wide application of these materials in sandwich‐type or lateral optoelectronic device architectures. Despite abundant research on the topic, the exact mechanisms underlying the dynamics of device performance remain elusive. Herein, photoluminescence (PL) and electric field‐induced second harmonic microscopy techniques are combined to image and identify voltage‐induced lateral dynamic processes in methylammonium lead iodide perovskite thin films. A sequence of voltage‐induced dynamic steps is observed: i) Appearance of a short‐lived bright PL next to the positive electrode; ii) formation of a moving dark PL front; iii) emergence and blinking of bright PL spots; iv) growth and subsequent decay of the bright PL spots after voltage turn off. This behavior is explained by proposing a model of varying spatial distribution of inter‐electrode electric field and the presence of two types of PL quenching defects.