Magnesium acetate additive enables efficient and stable carbon electrode based CsPbI2Br perovskite solar cells

Carbon electrode based hole transporting materials (HTM) free CsPbI2Br perovskite solar cells have advantages of excellent thermal stability and low cost. However, it is still a challenge to provide an effective strategy to realize highly efficient and stable HTM-free devices. Herein, a small amount (0.2-0.5% vs Pb source) of magnesium acetate (Mg(Ac)2) was introduced into the CsPbI2Br precursor solution. It was demonstrated that the carbonyl groups of Mg(Ac)2 can bind with all intrinsic elements of CsPbI2Br, leading to improved crystallinity and passivation of defects. Therefore, the power conversion efficiency of HTM-free devices was increased from 10.84% to 13.08%, along with an enhancement in device stability.