Atomic Structure and Electrical Activity of Grain Boundaries and Ruddlesden–Popper Faults in Cesium Lead Bromide Perovskite

Abstract

To evaluate the role of planar defects in lead‐halide perovskites—cheap, versatile semiconducting materials—it is critical to examine their structure, including defects, at the atomic scale and develop a detailed understanding of their impact on electronic properties. In this study, postsynthesis nanocrystal fusion, aberration‐corrected scanning transmission electron microscopy, and first‐principles calculations are combined to study the nature of different planar defects formed in CsPbBr3 nanocrystals. Two types of prevalent planar defects from atomic resolution imaging are observed: previously unreported Br‐rich [001](210)∑5 grain boundaries (GBs) and Ruddlesden–Popper (RP) planar faults. The first‐principles calculations reveal that neither of these planar faults induce deep defect levels, but their Br‐deficient counterparts do. It is found that the ∑5 GB repels electrons and attracts holes, similar to an n–p–n junction, and the RP planar defects repel both electrons and holes, similar to a semiconductor–insulator–semiconductor junction. Finally, the potential applications of these findings and their implications to understand the planar defects in organic–inorganic lead‐halide perovskites that have led to solar cells with extremely high photoconversion efficiencies are discussed.

Manganese‐Doping‐Induced Quantum Confinement within Host Perovskite Nanocrystals through Ruddlesden–Popper Defects

“…In addition, theoretical studies suggest that these R.P. planar defects behave like a semiconductor–insulator–semiconductor junction . In the present case, it is likely that the formation of R.P.…”

Recent Progress of All‐Bromide Inorganic Perovskite Solar Cells

“…The CsPbBr 3 atomic and electronic structures were described by surface science techniques corroborated by density functional theory (DFT) calculations . Furthermore, theoretical investigations of point defects and grain boundary‐induced trap states in CsPbBr 3 were reported to lead to shallow trap states within the bandgap demonstrating the superior electronic properties or defect‐tolerance property of CsPbBr 3 . Experimentally, efforts have been made to characterize the grain boundaries in CsPbBr 3 by electron microscopy techniques .…”

“…Further examination of the band diagrams across the grain boundary reveals that neither Br‐terminated nor RP planar faults induce deep defect levels in the bandgap. However, the Br‐deficient defects associated with the presence of Pb dangling bonds or Pb–Pb bonds were identified to lead to deep trap levels . Therefore, passivation of defective CsPbBr 3 surfaces is an important consideration for further boosting PCEs .…”

Anorganische CsPbX3‐Perowskit‐Solarzellen: Fortschritte und Perspektiven

“…10 msf ürd ie CVD-Schichten im Vergleich zu ca. [57] Diese Fehlertoleranz wurde auf das Fehlen einer bindenden/antibindenden Wechselwirkung zwischen Leitungs-und Va lenzband zurückgeführt. [49] FürC sPbI 3 ,d as durch Lçsungsverarbeitung abgeschieden wurde,w urden Lebensdauern von > 20 ns berichtet.…”

“…Wied ie hybriden HaPs ist auch CsPbX 3 ein defekttoleranter Halbleiter,d er seine elektronische Qualitäta uch bei Defekten beibehalten kann. [57] Diese Fehlertoleranz wurde auf das Fehlen einer bindenden/antibindenden Wechselwirkung zwischen Leitungs-und Va lenzband zurückgeführt. [58] Tr otz der oben genannten ¾hnlichkeiten zwischen den HaPs mit Cs-und organischen Kationen (was die dominierende Rolle des PbI 6 -Gerüsts gegenüber der Art des A-Kations demonstriert;s iehe auch Lit.…”