Multifunctional molecules of surfactant to support enhanced efficiency and stability for perovskite solar cells

As the darling of new era, perovskite solar cells (PSCs) have drawn extensive attention because of their tremendous commercial potentials. However, many different types of defects are easily formed during the fabrication process of perovskite films, such as cation and anion vacancy, under-coordinate metal ions, humidity erosion and so on, which are detrimental to the efficiency and long-term stability of the devices. To decrease the charge trap density and improve the moisture resistance of the perovskite film, here, we introduce a multifunctional surfactant, cetyl trimethyl ammonium bromide (CTAB), into perovskite precursor solution to both passivate the two types of ionic vacancies and also enhance the humidity resistance. Benefiting from Br and quaternary cetyl tertiary ammonium cations filled up on X- and A-sites, fluorescence spectrum revealed that moderate CTAB doped perovskite films showed decreased defects and inhibited carrier recombination. Consequently, ternary cation perovskite solar cells with optimized CTAB additives deliver an enhanced champion power conversion efficiency (PCE) of 20.54% and outstanding long-range stability with 94.3% of the initial efficiency after 2000 h without encapsulation in N2 atmosphere.