Lewis base manipulated crystallization for efficient tin halide perovskite solar cells

A facile Lewis base thiourea (TU) is introduced into the tin perovskite precursor to form a SnI 2 -TU intermediate to guide the crystallization kinetics, delivering a remarkably improved PCE and stability in tin halide perovskite solar cells. • Thiourea was applied to form a SnI 2 -TU intermediate to guide the crystallization kinetics. • The film morphology was improved and the non-radiative recombination is suppressed. • These benefits delivered a PCE of over 10% in inverted tin perovskite solar cells. • The unencapsulated device retained 90% of the initial efficiency after 1600 h in N 2 atmosphere. Tin halide perovskite is the most prospective lead-free perovskite material due to its close to ideal band gap and similar optoelectronic properties to the lead counterparts. Nevertheless, the lack of a regulated crystallization process leads to considerable defects and pinholes in those tin perovskite films, further deteriorating the achievable power conversion efficiency (PCE) for related solar cells. Herein, we employed a facile Lewis base thiourea (TU) into the perovskite precursor to form a SnI 2 -TU as an intermediate adduct to guide the crystallization kinetics, where the interaction between SnI 2 and TU was detected by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements, respectively. Improving the perovskite morphology with TU contributed to significant suppression of the non-radiative recombination and fast charge extraction through carrier dynamics analysis. These benefits delivered a remarkable PCE of over 10% in inverted tin perovskite solar cells, which was 24% higher than the original device. The unencapsulated device with TU retained 90% of the initial efficiency after over 1600 h in N 2 atmosphere.