Thiourea Small Molecules Regulated Slow Passivation in MAPbI3 Thin Films for Enhanced Stability and Performance of Perovskite Solar Cells

The low stability of perovskite solar cells is the limitingfactorfor their commercialization, which is largely affected by defectsoriginating from crystallographic distortions and interface formationin solution-processed lead halide perovskite thin films. Herein, ureaand thiourea small molecules are used as dopants to synergisticallyincrease the power conversion efficiency (PCE) and stability of theperovskite solar cells by regulating the morphology and crystallinityof the perovskite thin films. X-ray diffraction, atomic force microscopy,Fourier-transform infrared spectroscopy, transmittance spectra, day-dependentphotoluminescence (PL), and Raman scattering spectra are used to brieflycompare the crystal growth and defect passivation mechanisms of ureaand thiourea small molecules. The PCE of thiourea-doped perovskitesolar cells gradually increases as a function of storage duration,from 12.12 & PLUSMN; 0.15% to 18.38 & PLUSMN; 89% in 40 days. Day-dependentPL and Raman scattering spectra reveal that the crystallinity of thethiourea-doped perovskite thin film improves over time, resultingin slow passivation from thiourea small molecules and consequentlyan improvement in device performance.

Automated summary

By using urea and thiourea small molecules as dopants, the morphology and crystallinity of perovskite thin films are regulated, effectively improving the power conversion efficiency and stability of perovskite solar cells. The PCE of thiourea-doped perovskite solar cells gradually increases from 12.12% to 18.38% over a storage duration of 40 days.