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Interfacial Engineering Determines Band Alignment and Steers Charge Separation and Recombination at an Inorganic Perovskite Quantum Dot/WS2 Junction: A Time Domain Ab Initio Study.

Research paper by Siyu S Wang, Qiquan Q Luo, Wei-Hai WH Fang, Run R Long

Indexed on: 02 Mar '19Published on: 02 Mar '19Published in: Journal of Physical Chemistry Letters



Abstract

Using time-domain density functional theory and nonadiabatic (NA) molecular dynamics, we demonstrate that interfacial interaction between WS2 and CsPbBr3 quantum dots (QDs) determines the band alignment, leading to a type-II and type-I heterojunction for the WS2 contacting with Cs/Br- and PbBr2-terminated facet QD, respectively. In the type-II heterojunction, electron transfer is faster than hole transfer arising due to the stronger NA coupling, higher density of electron acceptor states, and more and higher phonon modes involved. Both the electron and hole transfer times are subpicosecond, in agreement with experiments. The energy lost by electron and hole are slower than charge transfer several times, facilitating to remain charge carries sufficiently "hot". Particularly, the electron-hole recombination occurs over 1 ns, favoring long-lived charge separated state. The detailed atomistic insights into the photoinduced charge and energy dynamics at the WS2/QD interface provide valuable guidelines for improving performance of perovskite/transition metal dichalcogenides solar cells.