High-performance hematite-integrated perovskite solar cells

We report high-performance organometallic perovskite solar cells (PSCs) utilizing a thermodynamically stable hematite (α-Fe₂O₃) as an electron transport layer (ETL). The incorporation of an α-Fe₂O₃ layer could provide suitable energy band alignment with the perovskite, as well as induce a deep valence band maximum, which promotes electron extraction from the conduction band of the perovskite and facilitates hole blocking. Using the solar cell capacitance simulator (SCAPS-1D) software for the optimized PSC under the typical AM 1.5G light spectrum, it was predicted to achieve a competitive power conversion efficiency (PCE) of 25.62% with a high short circuit current (J_SC) of 23.58 mA cm^-2, an open circuit voltage (V_OC) of 1.286 V, and a fill factor (FF) of 84.39%. Moreover, high thermal stability of PSCs with exposure to a high temperature of 85 °C can be attained. Through a series of optimization processes, we conclude that a thinner α-Fe₂O₃ layer (10 nm) improves charge extraction and the transmittance of the visible light, while the decreased defect density significantly reduces recombination rates, thereby enhancing V_OC and PCE. An optimum perovskite thickness of 800 nm was found to maximize light absorption. Additionally, controlled acceptor doping concentration (N_A) enhanced carrier extraction and quasi-Fermi level splitting (QFLS), while high series resistance (R_S) and low shunt resistance (R_SH) were demonstrated to limit FF and efficiency.