A Light Management Strategy for Perovskite Solar Cells: One-Step Wet-Chemical Etching of Nanoporous ITO Surface Layers

Given the interfacial Fresnel reflection caused by refractive-index mismatch between transparent conducting oxide (TCO) substrates and adjacent functional layers, introducing an antireflection interlayer for light management can provide an effective route to improve the performance of perovskite solar cells (PSCs). Here, we present a facile one-step wet-chemical etching strategy using dilute hydrochloric acid to fabricate a nanoporous architecture on indium tin oxide (ITO) surfaces. By tailoring the optical properties of two commonly used ITO substrates with different thicknesses, we obtain a broadband increase in absolute transmittance across the 350–1000 nm wavelength range. When applied to PSCs, the etched ITO substrate introduces a graded-refractive-index transition layer that reduces reflection losses and enhances light absorption, thereby increasing the short-circuit current density (JSC) of the p–i–n devices from 25.00 mA cm–2 and 25.02 mA cm–2 to 25.46 mA cm–2. In addition, the introduction of the nanoporous structure increases the effective interfacial contact area and is accompanied by possible changes in the interfacial chemical states and interactions, leading to an increase in the fill factor (FF) from 84.94% and 84.52% to 86.22%. Overall, the device fabricated on the etched ITO substrate achieves a champion power conversion efficiency (PCE) of 24.90%. This work demonstrates a mild, low-cost, and scalable ITO interface-engineering strategy for light management in PSCs and provides new insight into optical regulation in TCO-based optoelectronic devices, including thin-film solar cells, flat-panel displays, organic light-emitting diodes, and functional windows.