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

Using a fast and simple one-step electrochemical method, we developed transparent and conductive ZnO nanoporous layers encapsulating molecular catalysts, showcasing dual functionality as a window layer for thin-film solar cells and a catalytic layer for solar-to-fuel conversion. As a proof of concept, tetraammonium-substituted Co phthalocyanine (CoPcTA) was encapsulated into the window layer of high-efficiency Cu(In,Ga)Se₂ (CIGS) solar cells demonstrating photoelectrochemical (PEC) reduction of CO₂ into CO with a selectivity of 93% and current densities up to ca. 7 mA cm^–2 at −1.7 V vs SCE under 1 sun irradiation, which corresponds to a turnover number (TON) of above 100000 and a turnover frequency (TOF) of 10 s^–1 after 3 h. The simplicity and versatility of this approach make the nanoporous catalytic ZnO layer not only easily adaptable to different high-efficiency solar cells but also pave the way for flexible testing of diverse molecular catalysts for CO₂ conversion into diverse, valuable fuels.