The identification of deep-level defects that act as detrimental nonradiative recombination centers is critical for optimizing the optoelectronic performance of hybrid perovskites. Although extensive studies have been devoted to revealing the nature of deep-level defects in hybrid perovskites, it is still unclear what defects are responsible for the experimentally observed nonradiative recombination rates. Employing first-principles approaches, we quantitatively show that the iodine interstitial is a dominant nonradiative recombination center in methylammonium-lead iodide. This important insight points to a target for defect engineering in order to further improve the performance of hybrid perovskites.

Slow radiative recombination due to a slightly indirect band gap has been proposed to explain the high efficiency of lead-halide perovskite solar cells. Here, we calculate the radiative recombination rate from first principles for the prototypical lead-halide perovskite, MAPbI 3 (MA=CH 3 NH 3 ). Since the structure is dynamic, with the MA molecule rotating even at room temperature, we determine the momentum mismatch between the band edges as a function of the orientation of the MA molecule. Our results demonstrate that the indirect nature of the band gap suppresses the radiative recombination rate by less than a factor of two, and that the radiative recombination coefficient is as high as in traditional direct-gap semiconductors. Our study provides a rigorous assessment of the radiative recombination mechanisms and their relation to the high efficiency of lead-halide perovskite solar cells, and will provide a sound basis for accurate modeling.

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The emergence of halide perovskites for photovoltaic applications has triggered great interest in these materials for solid-state light-emission. Higher-order electron-hole recombination processes can critically affect the efficiency of such devices. In the present work, we compute the Auger recombination coefficients in the prototypical halide perovskite, CH 3 NH 3 PbI 3 (MAPbI 3), using first-This article is protected by copyright. All rights reserved. 2 principles calculations. We demonstrate that Auger recombination is responsible for the exceptionally high third-order recombination coefficient observed in experiment. We attribute the large Auger coefficient to a coincidental resonance between the band gap and interband transitions to a complex of higher-lying conduction bands. Additionally, we find that the distortions of PbI 6 octahedra contribute significantly to the high Auger coefficient, offering potential avenues for materials design.

Hybrid perovskites such as MAPbI (MA = CHNH) exhibit a unique spin texture. The spin texture (as calculated within the Rashba model) has been suggested to be responsible for a suppression of radiative recombination due to a mismatch of spins at the band edges. Here we compute the spin texture from first principles and demonstrate that it does not suppress recombination. The exact spin texture is dominated by the inversion asymmetry of the local electrostatic potential, which is determined by the structural distortion induced by the MA molecule. In addition, the rotation of the MA molecule at room temperature leads to a dynamic spin texture in MAPbI. These insights call for a reconsideration of the scenario that radiative recombination is suppressed and provide an in-depth understanding of the origin of the spin texture in hybrid perovskites, which is crucial for designing spintronic devices.