Light‐Harvesting Organic Nanocrystals Capable of Photon Upconversion

Abstract

Harvesting and converting low energy photons into higher ones through upconversion have great potential in solar energy conversion. A light‐harvesting nanocrystal assembled from 9,10‐distyrylanthracene and palladium(II) meso‐tetraphenyltetrabenzoporphyrin as the acceptor and the sensitizer, respectively effects red‐to‐green upconversion under incoherent excitation of low power density. An upconversion quantum yield of 0.29±0.02 % is obtained upon excitation with 640 nm laser of 120 mW cm−2. The well‐organized packing of acceptor molecules with aggregation‐induced emission in the nanocrystals dramatically reduces the nonradiative decay of the excited acceptor, benefits the triplet–triplet annihilation (TTA) upconversion and guides the consequent upconverted emission. This work provides a straightforward strategy to develop light‐harvesting nanocrystals based on TTA upconversion, which is attractive for energy conversion and photonic applications.

Tetraphenylethene 9,10‐Diphenylanthracene Derivatives – Synthesis and Photophysical Properties

“…The measured triplet lifetimes are therefore affected by both intramolecular and intermolecular decay processes. Nevertheless, the triplet lifetimes of the TPE‐DPA derivatives are comparable to those reported for other solid‐state TTA upconversion systems employing related AIE‐luminogens as emitters …”

“…AIE materials are very attractive for TTA‐UC applications, particularly in solid‐state devices since solid‐state TTA‐UC requires high chromophore concentration to achieve high Φ PL . AIE materials such as (2Z,2′Z)‐2,2′‐(1,4‐phenylene)bis(3‐phenylacrylonitrile) and 9,10‐distyrylanthracene (DSA) have been used as emitters in TTA‐UC systems . Given that DPA is an ideal emitter for TTA‐UC, we thus determined whether the TPE‐DPA derivatives could be used as emitters for solid‐state TTA‐UC.…”

Molecular doped organic semiconductor crystals for optoelectronic device applications

“…In 2017, Li et al prepared redto-green upconversion nanocrystals using 9,10distyrylanthracene and palladium(II) mesotetraphenyltetrabenzoporphyrin as the emitter and sensitizer, respectively. 66 An upconversion efficiency of 0.29% was obtained under the excitation at 640 nm with a laser intensity of 120 mW cm -2 . Very recently, Wong et al prepared upconversion crystals using platinum octaethylporphyrin (PtOEP) as the triplet donor, and 9,10-diphenylanthracene (DPA) and its derivatives as triplet acceptors (Fig.…”

“…Several attempts have been made to prepare crystalline upconversion systems. [66][67][68][69][70] The doping ratio of the donor molecule in the acceptor matrix plays a significantly important role in upconversion efficiency. With a low donor ratio, limited amounts of triplets are generated as the low absorptivity of the donor molecules.…”

Visible‐to‐Ultraviolet Light Conversion: Materials and Applications

“…TTA can produce low‐power excited emission with high quantum yield due to the strong absorption of organic sensitizers and a simple TTA process. [ 46 ] The realization of efficient TTA emission requires sensitizers with high ISC coefficients, long triplet excited state lifetimes, and weak absorption of emission lights. Efficient acceptors should have high fluorescence quantum yields, suitable energy triplet states, and long triplet state lifetimes.…”