Dark Singlet Exciton Sensitized Triplet Energy Transfer Across the CsPbBr₃ Nanoplate‐Organic Interface

Abstract

Semiconductor nanocrystals (NCs) sensitized triplet energy transfer (TET) provides a promising alternative for achieving efficient triplet-triplet annihilation up-conversion (TTA-UC). However, the study on the role of NC's exciton fine structure in TET, which is important to further enhance the TET efficiency, is still limited. Herein, the respective contribution of bright/dark exciton to TET using 1-naphthoic acid (mediator) decorated 2 nm thick CsPbBr 3 nanoplates as the model system is studied. The well-characterized and unique exciton fine structure and large bright-dark splitting energy of CsPbBr 3 nanoplates provide an ideal platform to unambiguously explore the TET between dark singlet exciton and mediator. By using time-resolved temperature dependent optical spectroscopy, the direct participation of dark singlet state in the TET process is proved and also point out that the dark singlet exciton to mediator TET is the major energy transfer pathway, which is due to the ill-defined nature of exciton's spin in strongly confined nanoplates and dark exciton's long intrinsic lifetime. Finally, in combination with 2,5-diphenyloxazole as annihilator, mediator decorated CsPbBr 3 nanoplates can convert visible to ultraviolet light with a maximum photon gain of 0.75 eV under a low threshold of ≈0.76 W cm −2 .

Ultraviolet Circularly Polarized Luminescence in Chiral Perovskite Nanoplatelet‐Molecular Hybrids: Direct Binding Versus Efficient Triplet Energy Transfer

“…Compared with pristine NPLs (the average PL lifetime of 3.6 ± 0.16 ns), the average PL lifetime of CsPbBr 3 NPLs/9-PCA (0.84 ± 0.02 ns) is shortened considerably due to the occurrence of TET-1 process from NPLs to surface-bound 9-PCA molecules; these values agree well with previous studies on related systems. [38,39,51] From TRPL decays, the rate of k TET-1 and its efficiency Φ TET-1 can be calculated as approximately 0.91 ns −1 and 76.7%, according to [38] :…”

“…[42] An apparent anti-Stokes shift is determined as 0.75 eV from the energy difference between the laser wavelength (450 nm) and the vibronic peak of PPO emission (353 nm), which is comparable to previously reported values and limited by the energy loss in the TET-2 process. [39,53] In the following experiment, UVCPL from the CsPbBr 3 NPLs/9-PCA/PPO was characterized under the excitations at 300 and 450 nm, respectively. Under the excitation of 300 nm, UVCPL is observed from the hybrids and shown in Figure 5C, exhibiting a similar low luminescence dissymmetry factor g lum (≈1.07 × 10 −4 ) as compared with the pristine CsPbBr 3 NPLs (g lum ≈1.82 × 10 −4 ).…”

“…Compared with pristine NPLs (the average PL lifetime of 3.6 ± 0.16 ns), the average PL lifetime of CsPbBr 3 NPLs/9‐PCA (0.84 ± 0.02 ns) is shortened considerably due to the occurrence of TET‐1 process from NPLs to surface‐bound 9‐PCA molecules; these values agree well with previous studies on related systems. [ 38,39,51 ] From TRPL decays, the rate of k TET‐1 and its efficiency Φ TET‐1 can be calculated as approximately 0.91 ns −1 and 76.7%, according to [ 38 ] : $$$$\begin{equation}{k}_{{\mathrm{TET}} - 1}\ = \ \frac{1}{{{\tau }_{{\mathrm{NPL\ }}/\ 9 - {\mathrm{PCA}}}}} - \frac{1}{{{\tau }_{{\mathrm{NPL}}}}}\end{equation}$$$$ $$$$\begin{equation}{{{\Phi}}}_{{\mathrm{TET}} - 1}\ = \ 1 - \frac{{{\tau }_{{\mathrm{NPL\ }}/\ 9 - {\mathrm{PCA}}}}}{{{\tau }_{{\mathrm{NPL}}}}}\end{equation}$$$$where τ NPL/9‐PCA and τ NPL denote the average PL lifetimes of CsPbBr 3 NPLs/9‐PCA hybrids and pristine NPLs, respectively. The latter value of the Φ TET‐1 can also be obtained taking into account the calculated PL quenching efficiency of ≈70.2% for CsPbBr 3 NPLs/9‐PCA shown in Figure 3B.…”

“…Moreover, when suitable triplet transmitters are anchored at the surface, UVCPL can be expected from triplet annihilators based on the triplet energy transfer (TET) and a subsequent triplet-triplet annihilation upconversion (TTA-UC) processes. [37][38][39][40][41] However, so far, there have been few reports on the realization of UVCPL in these nanocrystalmolecular hybrids either via direct binding or the TET process. In particular, it's critical to understand whether chiral light harvesting could occur through the TTA-UC process between the chiral inorganic nanocrystals and achiral annihilators.…”

Recent Advances in Triplet Energy Transfer between Organic Dyes and Lanthanide-Doped Luminescent Nanoparticles

“…The transfer of photonic energy among different materials is of significant importance to a variety of fields, ranging from photosynthesis, which is the key to life on earth, to lighting and displays that bring brightness to us. , As a result, continuous efforts have been devoted to energy transfer between materials since the first discovery of energy transfer over distances larger than collision radii in 1922. − Recently, an emerging type of energy transfer between organic dyes and inorganic nanomaterials, namely triplet energy transfer, has received increasing research enthusiasm because such energy transfer can merge the optical tunability of inorganic nanomaterials and the versatility of molecular design. ,,− Indeed, triplet energy transfer between organic dyes and inorganic nanomaterials has shown enormous potential in various photonic applications, including solar energy conversion, light-emitting devices, photocatalysis, and photodynamic therapy. ,,− For example, triplet energy transfer from quantum dots to organic dyes can initiate intense triplet–triplet annihilation photon upconversion, and a reversed process (i.e., triplet energy transfer from organic dyes to quantum dots) enables the harvest of molecules’ triplet energy for efficient solar cells. ,− …”