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Chemical bath deposition (CBD) is a widely used approach to deposit the tin oxide (SnO2) electron transport layer (ETL) in the perovskite solar cell (PSC). However, the defect states in the CBD‐resulted SnO2 ETLs limit the electron extraction/transport from the perovskite to the ETL and lead to poor PSC performance. Herein, ethylenediaminetetraacetic acid dipotassium (EDTA‐2K) is used as an additive in the CBD precursor of the SnO2 ETL, which results in the chelation of Sn2+ and EDTA during the hydrolysis process. This strategy decreases the concentration of free Sn2+ in the precursor for hydrolysis and slows down the CBD process, thus attributes to the decreased surface defect states as well as the enhanced conductivity of the ETL. As a result, the EDTA‐2K additive makes the CBD SnO2 ETL with efficient electron extraction and transporting capability. The champion device achieves a power conversion efficiency (PCE) of 21.87%, which is significantly higher than that of the pristine CBD SnO2‐based device (20.25%). In addition, the device with an active area of 1.21 cm2 achieves a high PCE of 19.23%. This strategy makes the CBD SnO2 an excellent ETL candidate for the development of low‐cost and large‐scale PSCs. [ABSTRACT FROM AUTHOR]

Wide bandgap (Eg) mixed‐halide perovskite has attracted much attention for applications in photovoltaic devices. However, devices featuring this type of perovskite are often subject to a large voltage deficit due to the occurrence of phase segregation, which limits the relevant devices' access to high performances. Here, the correlation of the phase segregation and voltage losses for wide‐Eg mixed‐halide perovskite solar cells (PSCs) is clarified by experiments and simulations. Taking 1.67 eV Eg mixed‐halide perovskite as an example, it is confirmed experimentally that the control devices produce a poor physical morphology, a locally widened Eg, and an inferior electrical response. By suppressing the phase segregation, the open‐circuit voltage (Voc) can be boosted from 1.15 to 1.20 V, which is a high value for the 1.67 eV Eg mixed‐halide PSCs. An electrical simulation of phase segregation reveals that the performance degeneration can be attributed to the bulk recombination due to the energy level mismatch of the varied Egs. Moreover, a theoretical perspective is produced to expatiate on the strategies for the high Voc of wide‐Eg PSCs. This study brings deep guidance to unlock the potential for high‐performance mix‐halide PSCs. [ABSTRACT FROM AUTHOR]