Correlated organic–inorganic motion enhances stability and charge carrier lifetime in mixed halide perovskites

Abstract

Organic cations are believed to have little influence on charge carrier lifetime in hybrid organic-inorganic perovskites. Experiments defy this expectation. We consider formamidinium lead iodide (FAPbI3) doping with and without...

Great Influence of Organic Cation Motion on Charge Carrier Dynamics in Metal Halide Perovskite Unraveled by Unsupervised Machine Learning

“…The projected density of states (PDOS) shows that the I and Pb atomic orbitals dominate the VBM and CBM, which are separated by a wide bandgap of 1.37 eV, agreeing with the experimental value (1.47 eV) and our previous works. , Therefore, Pb and I make the major and direct contribution to the NAC and lead to nonradiative electron–hole recombination. By contrast, the FA cation does not constitute the band edge states and indirectly affects the NAC via interacting with the electric field they created and correlated inorganic–organic motion. , This analysis is corroborated by the component-resolved band structure and charge densities of the VBM and CBM (Figure S1). Both the VBM and CBM are located at the Γ-point, which are mainly supported by the I and Pb atoms, respectively.…”

“…By contrast, the FA cation does not constitute the band edge states and indirectly affects the NAC via interacting with the electric field they created and correlated inorganic−organic motion. 33,34 This analysis is corroborated by the component-resolved band structure and charge densities of the VBM and CBM (Figure S1). Both the VBM and CBM are located at the Γ-point, which are mainly supported by the I and Pb atoms, respectively.…”

“…However, our previous work has shown that doping larger size A-site cations into three-dimensional perovskites enhances the lattice rigidity and, thus, delays charge recombination by reducing the NAC . Shortly after, we have further demonstrated that correlated motion in both HOIPs and all-inorganic perovskites can inhibit atomic motions, decrease the NAC, and suppress the nonradiative electron–hole recombination. , The contradiction between our simulated results and traditional view requires a deep understanding of how the individual geometric feature correlates with the NAC, bandgap, and electron–hole recombination, which has remained largely elusive. Machine learning (ML), including supervised and unsupervised ML, combined with traditional electronic structure calculation, has been recently appeared as a new paradigm in chemistry, materials, and physics.…”

Unveiling the Valence State of Interstitial Bromine on Charge Carrier Lifetime in CH3NH3PbBr3 by Quantum Dynamics Simulation

“…However, the atomic motion of Pb and Br atoms other than the interstitial bromine decrease in the Br i and Br i – systems and increase in the Br i + system compared to the case for MAPbBr 3 , because the negative interstitial bromine can stabilize the inorganic Br–Pb lattice; neutral interstitial bromine has little influence on it, whereas the positive interstitial bromine repels with Pb and causes the strong fluctuations of inorganic Br–Pb lattice. Overall, the correlated organic–inorganic motions make the atomic motions decrease as Br i + > Br i > Br i – > MAPbBr 3 . , The motion of neutral interstitial bromine is smaller than that of charged interstitial bromine ions, suggesting that the faster migrations of bromine ions than bromine atoms. − In general, the stronger atomic fluctuation is, the faster decoherence happens and the larger NA coupling presents. The two factors are opposite to each on affecting charge dynamics.…”

“…Overall, the correlated organic−inorganic motions make the atomic motions decrease as Br i + > Br i > Br i − > MAPbBr 3 . 48,49 The motion of neutral interstitial bromine is smaller than that of charged interstitial bromine ions, suggesting that the faster migrations of bromine ions than bromine atoms. 50−54 In general, the stronger atomic fluctuation is, the faster decoherence happens and the larger NA coupling presents.…”