Defect site engineering for charge recombination and stability via polymer surfactant incorporation with an ultra-small amount in perovskite solar cells

A reduction in defect sites that are produced in the process of perovskite crystallization is crucial for efficient perovskite solar cells. In this study, we incorporate an ultra-small amount (less than 0.1 wt%) of a non-volatile polymer additive, poly(ethylene glycol) tridecyl ether (PTE), into the perovskite precursor solution in order to regulate the crystallization kinetics. Even a tiny amount of PTE additives enables effectively to make film surface smooth, suppress charge recombination both between free charge carriers and between trapped and free charge carriers, and improve the electrical stability under continuous illumination. Our findings show that the defects are associated not only with charge recombination but also with electrical stability under illumination. Incorporating PTE additives, charge extraction is facilitated by a reduction in the loss of photogenerated charge carriers, leading to an improvement in photovoltaic efficiency with enhanced stability for the planar p-i-n perovskite solar cells.