Impact of Hydrogen Vacancies on Non-Radiative Recombination in Metal-Halide Perovskites.

Hydrogen vacancies (VH) were considered major nonradiative recombination centers in hybrid perovskites. By employing a multiscale approach that combines first-principles calculations and molecular dynamics simulations, our findings indicated that the VH impact was overestimated, due to the previous metastable VH configurations. The organic molecules with VH located on either the nitrogen or carbon atom, act as the ligands that form energetically stable dimers with Pb2+ cations. These dimers lower VH energy by 0.35-0.97 eV in MAPbI3 and by 0.88-1.01 eV in FAPbI3, compared to non-bonding configurations. These dimers significantly boosted potential energy barriers of hole capture, resulting in a dramatic reduction in carrier capture coefficients by over 10 orders of magnitude. Consequently, the total capture coefficients (Ctotal) for the dominant VH in MAPbI3 and FAPbI3 are on the order of 10-17 and 10-31 cm3s-1, respectively. By uncovering the negligible impact of VH on nonradiative recombination, this work shifts the focus toward more significant defects, for instance, iodine interstitial (with a capture coefficient on the order of 10-8- cm3s-1), thereby paving the way for optimizing perovskite solar cells efficiency to meet Shockley-Queisser limit.