In Situ Formation of 2D Perovskite Seeding for Record‐Efficiency Indoor Perovskite Photovoltaic Devices

Abstract With 40% efficiency under room light intensity, perovskite solar cells (PSCs) will be promising power supplies for low‐light applications, particularly for Internet of Things (IoT) devices and indoor electronics, shall they become commercialized. Herein, β‐alaninamide hydrochloride (AHC) is utilized to spontaneously form a layer of 2D perovskite nucleation seeds for improved film uniformity, crystallization quality, and solar cell performance. It is found that the AHC addition indeed improves film quality as demonstrated by better uniformity, lower trap density, smaller lattice stress, and, as a result, a 10‐fold increase in charge carrier lifetime. Consequently, not only does the small‐area (0.09 cm 2 ) PSCs achieve a power conversion efficiency of 42.12%, the large‐area cells (1.00 cm 2 , and 2.56 cm 2 ) attain efficiency as high as 40.93%, and 40.07% respectively. All of these are the highest efficiency values for indoor photovoltaic cells with similar sizes, and more importantly, they represent the smallest efficiency loss due to area scale‐up. This work provides a new method to fabricate high‐performance indoor PSCs (i‐PSCs) for IoT devices with great potential in large‐area printing technology.