Uncovering synergistic effect of chloride additives for efficient quasi-2D perovskite solar cells

Abstract

• MACl and PbCl 2 binary additives form MAPbCl 3 intermediate phase. • Perovskite crystallization is retarded and volatilization of MACl is prevented. • Such a synergistic effect leads to high-quality Q-2D perovskite films. • Charge recombination is suppressed and charge extraction efficiency is enhanced. • The champion PCE of 18.67% is one of the highest PCE for Q-2D RP PSCs with n ≤ 4. Methylammonium chloride (MACl) and lead chloride (PbCl 2 ) are commonly used for improving perovskite film quality. However, the rapid release of volatile MACl would lead to low-quality perovskite films with pinholes and defects. Here, we report a strategy of employing MACl&PbCl 2 binary additives together to prepare high-quality quasi-two-dimensional (Q-2D) Ruddlesden–Popper (RP) perovskite films. We found that MAPbCl 3 intermediate phase is formed via a reaction between MACl and PbCl 2 , which suppresses the fast volatilization of MACl, resulting in a compact and pinhole-free perovskite film with large grains. Moreover, the trap states are passivated via the incorporation of Cl – into the Q-2D perovskite crystals along with the addition of PbCl 2 , leading to a reduced charge recombination loss and an improved charge extraction. A remarkable power conversion efficiency (PCE) of 18.67% is achieved in such Q-2D RP PSCs, one of the highest PCE values among the low-dimensional RP PSCs with n ≤ 4. The environmental stability of the devices is also significantly enhanced. Our results provide an effective strategy by using chloride based additives for fabricating high-quality low-dimensional RP perovskite films for efficient solar cells.