Interfacial engineering by multifunctional ruthenium complex for CsPbI₂Br perovskite solar cells with a fill factor over 0.82

The interface is of paramount importance in heterostructures, as it can be considered as a device in accordance with Kroemer’s dictum. In perovskite solar cells (PSCs), optimizing the interface between the perovskite layer and the hole transport layer is known to be an effective method for enhancing PSC device performance. Herein, a metal ruthenium complex coded as C101 is introduced to the perovskite (CsPbI₂Br)/hole transport layer (PTAA) interface as a “charge driven motor” to selectively extract holes from CsPbI₂Br and then transfer them to PTAA, minimizing the voltage loss in PSCs. More significantly, the introduction of C101 layer effectively passivates the surface of CsPbI₂Br film and reduces the defect density of CsPbI₂Br film due to the covalent bond between the CsPbI₂Br and the–C=O group in C101. The photovoltaic performance of CsPbI₂Br PSCs is enhanced by 23.60% upon the introduction of C101 interfacial layer, with the champion CsPbI₂Br PSC exhibiting a power conversion efficiency of 14.96% in a reverse scan, a short-circuit current of 15.84 mA·cm⁻², an open-circuit voltage of 1.15 V, and a fill factor of 82.03%. Additionally, the introduction of C101 simultaneously enhances the humidity tolerance of CsPbI₂Br PSCs.