Performance and Stability of Polymer : Nonfullerene Solar Cells with 100 °C‐Annealed Electron‐Collecting Combination Layers

Abstract Inverted‐type organic solar cells, fabricated with low‐temperature‐processed combination layers of hybrid electron‐collecting buffer layers (ECBLs) consisting of zinc oxide (ZnO) and poly(2‐ethyl‐2‐oxazoline) (PEOz) and additional PEOz interlayers, showed improved performance and stability. The ZnO : PEOz precursor films with various PEOz compositions (0–12 wt %) were prepared and thermally treated at 100 °C, leading to the ECBLs on which the PEOz interlayers were subsequently deposited before coating of polymer : nonfullerene bulk heterojunction layers. Results showed that the power conversion efficiency of solar cells reached approximately 9.38 and 10.11 % (average) in case of the ZnO/PEOz and ZnO : PEOz(6 wt % PEOz)/PEOz combination layers, respectively, despite the low‐temperature thermal annealing process. A continuous irradiation test for 12 h under one sun condition (air mass 1.5G, 100 mW cm −2 ) disclosed that the devices with the ZnO : PEOz(6 wt % PEOz)/PEOz combination layers were more stable than those with the ZnO/PEOz layers.