High-efficiency α-FAPbI3 perovskite solar cells based on one-dimensional TiO2 nanorod array scaffolds

Formamidinium lead iodide (FAPbI3) presently shows great attraction for the light harvest in the high-efficiency perovskite solar cells (PeSCs) owing to the narrow energy band (1.45–1.51 eV), which a good approximation to the optimal Shockley-Queisser value. Unfortunately, the crystalline of the α-FAPbI3 is readily accompanied by a notorious non-perovskite yellow-phase (δ-FAPbI3), severely hindering the stability of the FAPbI3-based SCs. In this work, we first introduce one-dimensional TiO2 nanorod arrays (NAs) as the scaffolds in the PeSCs to guide the deposition of PbI2 and stabilize the α-FAPbI3. To further enhance the device performance, the phenylethylammonium iodide (PEAI) is used to passivate the surface defects of the perovskites. Finally, our optimized α-FAPbI3 PeSCs present excellent device performance with the PCE of up to 21.89% with weak hysteresis. Besides, our device retains ∼94% of the initial efficiency for 800 h kept under an air ambient with 20–30% relative humidity at room temperature in the dark. Our α-FAPbI3 SCs based on TiO2 NA scaffolds can be a reference for the development of low-temperature perovskite optoelectronic devices.