Anion effect on properties of Zn-doped CH3NH3PbI3 based perovskite solar cells

Abstract

High-quality perovskite films are crucial for developing efficient planar perovskite solar cells (PSCs). As-prepared perovskite films have low crystallinity and high level of trap densities, resulting in the deterioration of PSCs performances. Herein, a facile approach is adopted to fabricate high-quality CH 3 NH 3 PbI 3 films by incorporating different types of zinc salt, including zinc iodide (ZnI 2 ), zinc chloride (ZnCl 2 ), and zinc acetate (Zn(Ac) 2 ). It is demonstrated that zinc ions (Zn 2+ ) substitute a part of the lead ion (Pb 2+ ) sites, enlarging the grain size, and suppressing the formation of metallic lead. Moreover, the acetate anion bearing the carbonyl species (C O) effectively passivates the under-coordinated Pb 2+ defects and further reduces the defect densities at both the grain boundaries and interfaces. As a result, the planar PSCs with the Zn(Ac) 2 additive yield a champion power conversion efficiency (PCE) of 19.32%, which is 15% higher than that of the control device. Simultaneously, the outperforming device delivers remarkable stability, retaining 87% of its original efficiency after aging for 500 h under ambient conditions. • Enhanced Gibbs free energy of nucleation induced by zinc salt leads to larger grains. • A more stable perovskite lattice was obtained due to the partly replacement of Zn 2+ and Ac − . • The Ac − group takes superior role than I − and Cl − in passivating the under-coordinated Pb 2+ defects. • The synergistic effect of the Zn(Ac) 2 yields a PCE of 19.32%, enhancement of ∼15%.