Nonradiative Energy Transfer between Thickness-Controlled Halide Perovskite Nanoplatelets

Abstract

Despite showing great promise for optoelectronics, the commercialization of halide perovskite nanostructure-based devices is hampered by inefficient electrical excitation and strong exciton binding energies. While transport of excitons in an energy-tailored system via Förster resonance energy transfer (FRET) could be an efficient alternative, halide ion migration makes the realization of cascaded structures difficult. Here, we show how these could be obtained by exploiting the pronounced quantum confinement effect in two-dimensional CsPbBr3-based nanoplatelets (NPls). In thin films of NPls of two predetermined thicknesses, we observe an enhanced acceptor photoluminescence (PL) emission and a decreased donor PL lifetime. This indicates a FRETmediated process, benefitted by the structural parameters of the NPls. We determine corresponding transfer rates up to = 0.99 −1 and efficiencies of nearly = 70 %. We also show FRET to occur between perovskite NPls of other thicknesses. Consequently, this strategy could lead to tailored, enery cascade nanostructures for improved optoelectronic devices. TOC GRAPHICS 3 MAIN TEXT Halide perovskites are one of the hottest semiconducting materials for optoelectronic applications due to a range of fascinating properties. 1, 2 With bandgaps tunable throughout the visible range, 3 high absorption cross-sections, 4 and photoluminescence (PL) quantum yields approaching 100%, 5 potential uses range from solar cells 6, 7 and photodetectors 8 to light-emitting diodes (LEDs) 9, 10 and lasers 11 and even more exotic applications such as gamma-ray detectors 12 and remote thermometers. 13 With the initial focus on fabricating large-grain thin films for photovoltaics, fabrication has since spread to two-dimensional (2D) perovskite phases and nanocrystals (NCs). 14-17 These possess an additional tuning mechanism, as shrinking any dimension below the excitonic

White Electroluminescence from Perovskite–Organic Heterojunction

“…The energy band characteristics of both CsPBA-2 and SPR-001 were verified using ultraviolet photoelectron spectroscopy (UPS) which reveals the formation of a type I heterojunction (Figure 1c and Figure S1). This, coupled with the existence of a spectral overlap between the CsPBA-2 photoluminescence and SPR-001 absorbance spectra (Figure 1d), 16,31 supports the probability of non-radiative ET occurring, which further highlights the importance of spatial separation for effective white emission. The bilayered films are prepared by incorporating various concentrations of SPR-001 into the antisolvent and dripping it onto the sample midway during the spincoating of CsPBA-2 (Figure 2a).…”

NIR-excitable heterostructured upconversion perovskite nanodots with improved stability

“…Indeed, the fluorescence average lifetime reduction of the blue emission at 478 nm from 0.66 ms of the NaYF 4 :30%Yb,0.5%Tm nanocrystals to 0.29 ms of the CsPbBr 3 –NaYF 4 :Yb,Tm nanocrystals (Supplementary Fig. 16 and Supplementary Table 5 ) suggested that the energy transfer from NaYF 4 :Yb,Tm to CsPbBr 3 in the heterostructure follows a typical FRET process 27 , 41 . The FRET efficiency can be calculated with the equation Eff = 1 − τ D–A /τ D , where Eff is the energy transfer efficiency, τ D–A is the effective lifetime of a donor conjugated with an acceptor, and τ D is the effective lifetime of a donor in the absence of an acceptor.…”

Exciton‐Mediated Energy Transfer in Heterojunction Enables Infrared Light Photocatalysis

“…[33] Timeresolved fluorescence spectra of BP/CN in Figure 3b shows af aster radiation recombination to pristine CN nanosheet, representing the decreased lifetime of singlet excitons in BP/ CN. [1,34] As triplet excitons are derived from the intersystem crossing (ISC) progress of singlet excitons,low singlet exciton yield in the system directly leads to low triplet exciton concentration, and the reduction of triplet excitons will further reduce the probability of triplet-triplet annihilation (TTA) process. [35] In this case,t he BP/CN heterojunction exhibits weakened P-type delayed phosphorescence at low temperature (Figure 3c)w ith lifetime of about 1.48 ms (Figure 3d), lower than that of pristine CN (ca.…”

“…This couplings are crucial to the energy re‐balance mediated by both exciton‐based energy transfer and carrier‐based charge transfer in the system [33] . Time‐resolved fluorescence spectra of BP/CN in Figure 3 b shows a faster radiation recombination to pristine CN nanosheet, representing the decreased lifetime of singlet excitons in BP/CN [1, 34] . As triplet excitons are derived from the intersystem crossing (ISC) progress of singlet excitons, low singlet exciton yield in the system directly leads to low triplet exciton concentration, and the reduction of triplet excitons will further reduce the probability of triplet–triplet annihilation (TTA) process [35] .…”