Multifunctional Photovoltaic Window Layers for Solar-Driven Catalytic Conversion of CO₂: The Case of CIGS Solar Cells

Using a fast and simple one-stepelectrochemical method, we developedtransparent and conductive ZnO nanoporous layers encapsulating molecularcatalysts, showcasing dual functionality as a window layer for thin-filmsolar cells and a catalytic layer for solar-to-fuel conversion. Asa proof of concept, tetraammonium-substituted Co phthalocyanine (CoPcTA)was encapsulated into the window layer of high-efficiency Cu(In,Ga)Se-2 (CIGS) solar cells demonstrating photoelectrochemical (PEC)reduction of CO2 into CO with a selectivity of 93% andcurrent densities up to ca. 7 mA cm(-2) at -1.7V vs SCE under 1 sun irradiation, which corresponds to a turnovernumber (TON) of above 100000 and a turnover frequency (TOF) of 10s(-1) after 3 h. The simplicity and versatility ofthis approach make the nanoporous catalytic ZnO layer not only easilyadaptable to different high-efficiency solar cells but also pave theway for flexible testing of diverse molecular catalysts for CO2 conversion into diverse, valuable fuels.