First-Principles Modeling of Defects in Lead Halide Perovskites: Best Practices and Open Issues

Abstract

Lead-halide perovskites are outstanding materials for photovoltaics, showing long lifetimes of photo-generated carriers which induce high conversion efficiencies in solar cell and light-emitting devices. Native defects can severely limit the efficiency of optoelectronic devices by acting as carrier recombination centers. The study of defects in lead halide perovskites thus assumes a prominent role in further advancing the exploitation of this class of materials. The perovskites defect chemistry has been mainly investigated by computational methods based on Density Functional Theory. The complex electronic structure of perovskites, however, poses challenges to the accuracy of such calculations. In this work we review the state of the art of defects calculations in lead halide perovskites, discussing the major technical issues commonly encountered and what we believe to be the best practices. By keeping as a test case the prototype MAPbI 3 compound, we discuss the impact of exchange-correlation functional on the electronic structure and on the defect

Reducing Detrimental Defects for High‐Performance Metal Halide Perovskite Solar Cells

“…Therefore, efforts have been made in the direction to minimize the defect density by well‐controlled semiconductor fabrication technology. The reported conventional semiconductors has defect densities of 10 14 cm −3 (polycrystalline Si), 10 13 cm −3 (CIGS), 10 15 cm −3 (CdTe) . Unlike crystalline Si solar cells, which are fabricated via a well‐controlled semiconductor manufacturing technology, perovskite solar cells are fabricated via a solution‐based methods (e.g., spin‐coating, blade‐coating, spray‐coating) and vapor‐based techniques where the crystal‐growth kinetics are generally fast .…”

Rationalizing the Molecular Design of Hole‐Selective Contacts to Improve Charge Extraction in Perovskite Solar Cells

“…[32] Following absorption of a photon, an electron and hole pair is generated. [3,4] This explains the long electron-hole lifetime in perovskite film. Most of these trap states are shallow in lead-halide perovskites, which means the captured electrons and holes can be released in a short time scale in the range of nanoseconds.…”

“…Most of these trap states are shallow in lead-halide perovskites, which means the captured electrons and holes can be released in a short time scale in the range of nanoseconds. [3,4] This explains the long electron-hole lifetime in perovskite film. [33] Radiative recombination happens in a very short time, and normally appears as a power-law decay in the TRPL measurement, whereas the non-radiative recombination by monomolecular shows a monoexponential decay in the TRPL measurement.…”

Extending Carrier Lifetimes in Lead Halide Perovskites with Alkali Metals by Passivating and Eliminating Halide Interstitial Defects

“…Quantum dynamics simulations show that elimination of the mid‐gap trap state by oxidation of I i to I i − prolongs carrier lifetimes . Unfortunately, I i − is unstable under light illumination, since the negative interstitial iodine can readily trap a hole to transform to the neutral iodine interstitial, lowering perovskite device performance . De Angelis and co‐authors have explored more iodine oxidation states in order to elucidate whether the nonradiative energy losses can be reduced .…”

“…Theory indicates that adjusting the oxidation state of the interstitial iodine can control carrier dynamics and reduce nonradiative carrier recombination. [12,17,20] Quantum dynamics simulations show that elimination of the mid-gap trap state by oxidation of I i to I i À prolongs carrier lifetimes. [18] Unfortunately,I i À is unstable under light illumination, [17b] since the negative interstitial iodine can readily trap ahole to transform to the neutral iodine interstitial, lowering perovskite device performance.…”