Nonradiative recombination induced by high-density defects in perovskite films is a bottleneck that impedes the improvement of photovoltaic performance in inverted-structure perovskite solar cells (PSCs). In this work, an effective strategy based on antisolvent (ethyl acetate) additive engineering with 3-fluorophenylethylammonium iodide (m-F-PEAI) for modulating perovskite crystal growth and passivating defects is proposed. The results of the experimental and theoretical analyses indicate that the unique fluorinated aromatic amine structure in m-F-PEAI can form a directed hydrogen-bonding network with FAI to retard the rapid grain growth of perovskite film. Its electron-rich F-terminal group is preferentially anchored at the (100) crystal plane, forming a large-grained perovskite film with optimal crystal orientations at the (100) crystal plane. The F atom located on the benzene ring of m-F-PEAI presents a negative electrostatic potential (ESP), which can act as a Lewis base to passivate uncoordinated Pb2+ (a Lewis acid defect) in perovskite films. At the same time, in situ filling of iodide ions reduces the halogen vacancy concentration and decreases the interfacial defect state density. In addition, m-F-PEAI reduces the work function of the perovskite films, facilitating electron migration from the perovskite films to C60. Thus, the suppression of nonradiative recombination remarkably yields a device efficiency of 26.41%. The optimized devices also exhibit excellent long-term stability under thermal stress and continuous light illumination.
Su et al. (Mon,) studied this question.