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

Formamidinium lead iodide (FAPbI(3)) 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 alpha-FAPbI(3) is readily accompanied by a notorious non-perovskite yellow-phase (delta-FAPbI(3)), severely hindering the stability of the FAPbI(3)-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 alpha-FAPbI(3). To further enhance the device performance, the phenyl-ethylammonium iodide (PEAI) is used to passivate the surface defects of the perovskites. Finally, our optimized alpha-FAPbI(3) PeSCs present excellent device performance with the PCE of up to 21.89% with weak hysteresis. Besides, our device retains similar to 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 alpha-FAPbI(3) SCs based on TiO2 NA scaffolds can be a reference for the development of low-temperature perovskite optoelectronic devices.

Automated summary

In this study, one-dimensional TiO2 nanorod arrays were used as scaffolds in PeSCs, guiding the deposition of PbI2 and stabilizing the alpha-FAPbI(3) crystalline structure. Additionally, phenyl-ethylammonium iodide was used to passivate the surface defects of the perovskites to enhance device performance. The optimized alpha-FAPbI(3) PeSCs achieved a power conversion efficiency of up to 21.89% with weak hysteresis, and retained 94% of the initial efficiency after 800 hours of storage in a dark room at room temperature. The alpha-FAPbI(3) SCs based on TiO2 nanorod scaffolds can serve as a reference for the development of low-temperature perovskite optoelectronic devices.