17% efficient printable mesoscopic PIN metal oxide framework perovskite solar cells using cesium-containing triple cation perovskite

Abstract

Fully printable perovskite solar cells (PSCs) based on an inorganic metal oxide architecture have attracted tremendous attention due to its feature of showing principally high stability. However, fully printable PSCs show a lower power conversion efficiency (PCE) than the thin film PSCs owing to the thick mesoscopic layers that pose an obstacle to charge collection. Herein, the triple cation perovskite Cs_0.05(FA_0.4MA_0.6)_0.95PbI_2.8Br_0.2, for the first time, is introduced in fully printable PSCs on the basis of a mesoporous metal oxide TiO₂/Al₂O₃/NiO layered framework with a carbon counter electrode. We found that partial replacement of FA/MA by Cs could increase the bandgap and exciton binding energy of Cs_x(FA_0.4MA_0.6)_1−xPbI_2.8Br_0.2 perovskite. An optimal efficiency of 17.02% can be obtained using Cs_0.05(FA_0.4MA_0.6)_0.95PbI_2.8Br_0.2 as the light absorber under AM 1.5G 100 mW cm⁻² light illumination, which, to the best of our knowledge, represents the highest efficiency observed to date for fully printable PSCs using a carbon counter electrode. Detailed investigations with nanosecond transient absorption spectroscopy and transient photovoltage/photocurrent decay measurements revealed that the presence of Cs in perovskite compounds can increase the charge carrier lifetime along with diffusion length, benefiting charge transport in thick mesoscopic layers. Furthermore, the Cs_0.05(FA_0.4MA_0.6)_0.95PbI_2.8Br_0.2-based PSCs exhibit good stability with a retention of over 90% initial PCE after 1020 h in dark conditions at 85 °C.