Recent Advances in Chemical Bath Deposition of Electron and Hole Transport Layers for Perovskite Solar Cells and Modules

ABSTRACT The development of high‐efficiency, stable, and scalable perovskite solar cells/perovskite solar modules (PSCs/PSMs) highly depends on the performance and cost‐effectiveness of functional layers such as electron transport layers (ETLs) and hole transport layers (HTLs). Among various deposition techniques, chemical bath deposition (CBD) has emerged as a promising low‐cost, solution‐based method for fabricating both ETLs and HTLs, offering advantages such as uniform film coverage and tunable material properties. In this review, we systematically summarize recent progress in employing CBD‐based ETLs/HTLs in PSCs/PSMs, with an emphasis on film growth mechanisms, deposition procedures, scalable fabrication, interface engineering strategies, and device performance. Particular attention is devoted to widely used materials, including SnO 2 , TiO 2 , and CdS for ETLs, as well as NiO x for HTLs. The effects of key parameters in the CBD technique, such as precursor concentration, temperature, and deposition duration, on film morphology and overall device performance are critically evaluated. Furthermore, this review explores the integration of CBD‐based ETLs/HTLs into scalable PSMs and assesses their impact on both efficiency and long‐term stability. Finally, current challenges and prospects for leveraging the CBD technique in the commercial development of PSCs/PSMs are discussed.