The design and performance optimization of all-inorganic CsPbIBr2/CsSnI3 heterojunction perovskite solar cells

With the fast growth of perovskite solar cells (PSCs), inorganic perovskite, represented by Cs-based perovskite, consistently surpasses organic perovskite solar cells in regards of photovoltaic performance. Among them, CsPbIBr2 materials stand out for their excellent efficiency and stability in all-inorganic PSCs. Unfortunately, poor solar energy utilization results from the CsPbIBr2′s wide band gap, which severely limits light harvesting. This work proposes an all-inorganic CsPbIBr2/CsSnI3 heterojunction using CsSnI3 instead of HTL based on the matched band structure of CsSnI3 and CsPbIBr2, then simulations and optimizes it using SCAPS-1D software to increase solar energy utilization and cell efficiency. The results show that the CsPbIBr2/CsSnI3 perovskite heterojunction PSC extends the absorption spectral wavelength range from 600 nm in the visible area to 960 nm in the near-infrared region, which greatly improves solar energy utilization and is more favorable to photogenerated carrier migration. The device's performance is ideal after optimization when Voc = 1.0344 V, Jsc = 39.36 mA/cm2, FF = 89.43%, and PCE = 36.41%. The device efficiency of the optimized CsPbIBr2/CsSnI3 heterojunction is 36.41%, which is significantly higher than the PCE of 5.45% for a single layer of CsPbIBr2. Moreover, the CsPbIBr2/CsSnI3 solar cell can respond to near-infrared light, enabling it to generate power at night. Consequently, this work reveals that the constructed CsPbIBr2/CsSnI3 heterojunction PSCs can enable the bright future of Cs-based inorganic PSCs for practical applications in photovoltaics and optoelectronics.