Chemical inhibition of reversible decomposition for efficient and super-stable perovskite solar cells

Despite the remarkable photovoltaic characteristics and printability of perovskite solar cells, their intrinsic instability has been the most serious drawback toward future commercialization. In this work, we have investigated the stability of perovskite films in terms of morphology, electronic properties and chemical compositions. Specifically, the chemical decomposition inhibition strategy was introduced in perovskite films through iodine bromide to modify the crystal defects, leading to PSCs with suppressed hysteresis effects, superior durability and attractive PCE of 21.5%. Femto-second transient absorption spectra and GIWAXS measurements provide deep insight into the reduced carrier recombination and indicate the improved crystallinity of the modified perovskite films. Furthermore, an efficient hole-transporting material, PDPP4T, without using any doping process is applied to achieve PSCs with enhanced open-circuit voltage and better repeatability. As a consequence, the modified PSCs could maintain 82% of their initial efficiency after 5000 h of storage in ambient conditions and 90% of their initial efficiency after 1000 h of light soaking process. An excellent water resistance up to 100 h of the PSCs is also obtained by encapsulation technology. Besides, after coating Ce3+-CsPbI3 nanocrystals as luminescent down-shifting layers on the front side of the PSCs, the PCE of the device was further improved to 22.16%.