Annealing-Free Cr₂ O₃ Electron-Selective Layer for Efficient Hybrid Perovskite Solar Cells

The electron-selective layer (ESL) plays a pivotal role in the performance of perovskite solar cells (PSCs). In this study, amorphous dispersible chromium oxide (Cr₂ O₃ ) nanosheets are synthesized by a facile solvothermal reaction, and a Cr₂ O₃ ESL is prepared by spin-coating Cr₂ O₃ ink on fluorine-doped tin oxide substrates without need for further annealing. By using Cr₂ O₃ as the electron-selective layer and Cs_0.05 (MA_0.17 FA_0.83 )_0.95 Pb(I_0.83 Br_0.17 )₃ as the light-absorption layer, a planar hybrid perovskite solar cell is fabricated. The spin-coating speed is optimized, the structure and morphology of samples are observed, the photoelectrical properties of ESLs are characterized, and the photovoltaic behaviors of devices are measured. Results show that the as-prepared Cr₂ O₃ layer has high optical transmittance and superb electron extraction and carrier transport property. The planar hybrid PSC based on the optimized Cr₂ O₃ ESL achieves a power conversion efficiency of 16.23 %, which is comparable to devices based on a conventional high-temperature-calcined TiO₂ ESL. These results demonstrate a low-cost and facile route to highly effective perovskite solar cells.