Visualizing Interfacial Energy Offset and Defects in Efficient 2D/3D Heterojunction Perovskite Solar Cells and Modules.

Currently, the full potential of perovskite solar cells (PSCs) is limited by charge-carrier recombination owing to imperfect passivation methods. Here, the recombination loss mechanisms owing to the interfacial energy offset and defects are quantified. The results show that a favorable energy offset can reduce minority carriers and suppress interfacial recombination losses more effectively than chemical passivation. To obtain high-efficiency PSCs, two-dimensional (2D) perovskites are promising candidates, which offer powerful field effects and require only modest chemical passivation at the interface. The enhanced passivation and charge-carrier extraction offered by the 2D/3D heterojunction PSCs has boosted their power conversion efficiency to 25.32% (certified 25.04%) for small-size devices and to 21.48% for a large-area module (with a designated area of 29.0 cm 2 ). Ion migration is also suppressed by the 2D/3D heterojunction, such that the unencapsulated small-size devices maintain 90% of their initial efficiency after 2000 h of continuous operation at the maximum power point. This article is protected by copyright. All rights reserved.