Efficient and Stable Perovskite Solar Cells by B-Site Compositional Engineered All-Inorganic Perovskites and Interface Passivation

Perovskite solar cells (PSCs) have emerged as a cost-effective solar technology in the past years. PSCs by three-dimensional hybrid inorganic-organic perovskites exhibited decent power conversion efficiencies (PCEs); however, their stabilities were poor. On the other hand, PSCs by all-inorganic perovskites indeed exhibited good stability, but their PCEs were low. Here, the development of novel all-inorganic perovskites CsPbI₂Br:xNd³⁺, where Pb²⁺ at the B-site is partially heterovalently substituted by Nd³⁺, is reported. The CsPbI₂Br:xNd³⁺ thin films possess enlarged crystal sizes, enhanced charge carrier mobilities, and superior crystallinity. Thus, the PSCs by the CsPbI₂Br:xNd³⁺ thin films exhibit more than 20% enhanced PCEs and dramatically boosted stability compared to those based on pristine CsPbI₂Br thin films. To further boost the device performance of PSCs, solution-processed 4-lithium styrenesulfonic acid/styrene copolymer (LiSPS) is utilized to passivate the surface defect and suppress surface charge carrier recombination. The PSCs based on the CsPbI₂Br:xNd³⁺/LiSPS bilayer thin film possess reduced charge extraction lifetime and suppressed charge carrier recombination, resulting in 14% enhanced PCEs and significantly boosted stability compared to those without incorporation of the LiSPS interface passivation layer. All these results indicate that we developed a facile way to approach high-performance PSCs by all-inorganic perovskites.