Energy Transfer in Stability-Optimized Perovskite Nanocrystals

Outstanding optoelectronic properties and a facile synthesis render halide perovskite nanocrystals (NCs) a promising material for nanostructure-based devices. However, the commercialization is hindered mainly by the lack of NC stability under ambient conditions and inefficient charge carrier injection. Here, we investigate solutions to both problems based on two different types of CsPbBr₃ perovskite: 2D nanoplatelets (NPls) and NCs encapsulated in polymer core-shell micelles. Thin films of NPls with two different thicknesses show enhanced acceptor photoluminescence (PL) emission and a decreased donor PL lifetime, confirming an energy transfer process based on Förster Resonance Energy Transfer (FRET). Due to the morphology of the NPls, transfer efficiencies reach up to η_FRET= 70%.[1] To increase stability of these films against moisture and ion migration, we employ electron beam lithography, which induces C=C bonding between the organic ligands of neighboring NPls.<br/>The NCs synthesized within block copolymer micelles, already show significantly enhanced stability induced by the polymer shell.[2] Further, we confirm that the shell does not prohibit energy transfer, as FRET efficiencies between these NCs and 2D NPls also reach up to 70%. However, this value is strongly correlated to the shell thickness: A thinner polymer shell enables increased FRET efficiency but insufficient protection against environmental effects.<br/>Notably, the improved stability of both NC types is advantageous for optoelectronic integration. The protection against halide ion migration combined with excellent energy transfer properties could lead to the realization of tailored energy funnels with enhanced carrier densities for high power applications.<br/><br/>[1] A. Singldinger et al., ACS Energy Letters 5, 1380-1385 (2020)<br/>[2] V. A. Hintermayr, C. Lampe et al., Nano Letters 19, 4928-4933 (2019)