Efficient micrometer thick bifacial perovskite solar cells

Perovskite solar cells have become promising candidates for thin-film photovoltaics (PV), but many record cells suffer from losses in current (≈3-4 mA cm${}^{-2}$). This is due to the choice of superstrate configurations (i.e., glass-side illumination) and thin absorber layers, typically on the order of ≈500 nm. Illumination through a top transparent conductive oxide electrode (substrate configuration) using LiF and Al${}_2$O${}_x$ as anti-reflective coatings leads to reflectance losses below 1% is demonstrated. When combined with 1 µm thick absorber layers, substrate configurated bifacial devices have power conversion efficiencies >20%, with minimized reflection losses approaching 98% of their detailed-balance limits and higher Jsc than their monofacial counterparts. Further analysis is conducted to show there is still a significant fraction of current lost due to poor charge-carrier extraction (e.g., resistive or low mobility contacts). This is studied by a direct comparison of photoluminescence at short-circuit versus open-circuit estimating a 4.5% loss in charge-carrier collection. (© 2024 The Authors. Advanced Energy Materials published by Wiley‐VCH GmbH)