Taurine as a powerful passivator of perovskite layer for efficient and stable perovskite solar cells

Abstract

Due to the ionic lattice property and the solution manufacture process of the perovskite light absorbing layer, there are several intrinsic defects (such as vacancies and low coordination Pb²⁺ and I⁻) in perovskite films, which cause undesired photon-generated carrier recombination in the perovskite solar cells (PSCs) and seriously affect the power conversion efficiency (PCE) of devices. Defect passivation strategy is one of the most effective ways to eliminate the defects in perovskite films. Herein, a multifunctional Taurine molecule was introduced into CH₃NH₃PbI₃ (MAPbI₃) perovskite precursor solution to passivate the defects. It was found that Taurine with sulfonic acid (–SOOOH) and amino (–NH₂) groups can bind with uncoordinated Pb²⁺ and I⁻ ions, respectively, which can significantly reduce the defect density and suppress the carrier non-radiative recombination. Under atmospheric environment, non-hole transport layer FTO/TiO₂/perovskite/carbon structure PSCs were prepared. The device with Taurine showed a PCE of 13.19%, which is 17.14% higher than that of the control device (11.26%). With the suppressed defects, the Taurine passivated devices also showed enhanced device stability. The unencapsulated Taurine passivated device stored in ambient air after 720 h (temp. ∼25 °C and RH ∼25%) maintained 58.74% original PCE, while that of the control device was only about 33.98%.