Hydrogen-Anion-Induced Carrier Recombination in MAPbI₃ Perovskite Solar Cells

Abstract

Identification and passivation of defect-induced electron–hole recombination centers are currently crucial for improving the efficiency of hybrid perovskite solar cells. Besides general intrinsic defects, experimental reports have indicated that hydrogen interstitials are also abundant in hybrid perovskite layers; however, few reports have evaluated the effect of such defects on the charge carrier recombination and device efficiencies. Here, we reveal that under I-poor synthesis conditions, the negatively charged monatomic hydrogen interstitial, H i –, will form in the prototypical CH3NH3PbI3 perovskite layer, acting as a detrimental deep-level defect, which leads to efficient electron–hole recombination and lowers the cell performance. We further rationalize that Br doping can mitigate the large atomic displacement caused by the presence of H i – and hence suppress the formation of the deep localized state. The results advance the knowledge of the deep-level defects in hybrid perovskites and provide useful information for enhancing solar cell performance by defect engineering.

Constructing a conjugated bridge for efficient electron transport at the interface of an inorganic–organic hetero-junction

“…This phenomenon is due to the excessive surface defects caused by the high doping amount that leads to easy electronhole recombination and inhibits the transfer of electrons. 47 As revealed in Fig. S14, † 0.1CD@N 3 -COF exhibited excellent photocatalytic H 2 evolution durability aer four recycles.…”

Hydrogen‐Induced Nonradiative Recombination in All‐Inorganic CsPbI3 Perovskite Solar Cells

“…Notably, in CsPbI 3 tends to be ionized into an electrically active negative‐U system, [ 25 ] similar to the case in many traditional semiconductors [ 20 ] and hybrid perovskites. [ 26,27 ] The sequence of the equilibrium state is the positive‐charged followed by the negative‐charged , because the Fermi level can change from p‐type to n‐type, while the neutral‐state is energetically unstable over the whole Fermi‐level range. The transition energy level , that is, the intersection of the formation energies of and , is located at 0.74 eV above the valance band maximum (VBM).…”

“…This is slightly different from the situation in the prototypical hybrid perovskite MAPbI 3 , in which is located in the proximity of the I atom. [ 26,27 ] In CsPbI 3 , the two nearby I atoms move closer to the hydrogen species, causing a slight distortion of the lattice. Correspondingly, the calculated IH bond lengths for this position are 1.96 and 2.17 Å, respectively.…”

Cation-Doping in Organic–Inorganic Perovskites to Improve the Structural Stability from Theoretical Prediction

“…29 Liang et al simulated Br doping into MAPbI 3 to mitigate the atomic displacement caused by the hydrogen interstitial, thereby inhibiting the formation of deep local states. 30 Haruyama et al replaced a part of methylammonium cations (MA + ) by formamidinium (FA + ) cations, which suppressed the hysteresis of the photosensitizer and ion migration in perovskite for solar cells. 31 A number of research groups optimized the abovementioned alternatives and proposed a doping scheme by mixing different A-site cations, and achieved better results.…”

“…Yang et al used Lewis acid tris-pentafluorophenyl-phosphine to treat the perovskite surface and passivate the under-coordinated halide ions by fluorine atoms . Liang et al simulated Br doping into MAPbI 3 to mitigate the atomic displacement caused by the hydrogen interstitial, thereby inhibiting the formation of deep local states . Haruyama et al replaced a part of methylammonium cations (MA + ) by formamidinium (FA + ) cations, which suppressed the hysteresis of the photosensitizer and ion migration in perovskite for solar cells …”