Performance improvement of dye-sensitized double perovskite solar cells by adding Ti3C2Tx MXene

Cs 2 AgBiBr 6 is considered an emerging candidate for lead-free inorganic double perovskite solar cells (PSCs). However, the photovoltaic performance of Cs 2 AgBiBr 6 is restricted while the reported power conversion efficiencies (PCEs) are almost lower than 3%. Here, we employed D149 indoline dye to sensitize the TiO 2 electron transport layer (ETL) and introduced Ti 3 C 2 T x MXene nanosheets into Cs 2 AgBiBr 6 to enhance its crystallization. Both Cs 2 AgBiBr 6 and D149 indoline dye could contribute to the photocurrent. Moreover, the calculations of the interface properties and electron structure were carried out based on density functional theory. Weak van der Waals forces between the interfaces of Cs 2 AgBiBr 6 and Ti 3 C 2 T x allow the perovskite to retain its semiconductor properties, while effectively weaken the Fermi level pinning (FLP). The high work function of Ti 3 C 2 T x adjusts the valence band of Cs 2 AgBiBr 6 through the Fermi level to improve carrier mobility. As a result, PCEs of 4.47 % under 1 sun illumination and 7.23 % under 200 lx indoor light illumination with enhanced long-term stability were achieved. Hence, this work demonstrates the great potential of Ti 3 C 2 T x for double PSCs and predicts other MXenes with higher work function for further applications.