Kinetically controlled crystal growth approach to enhance triplet energy migration-based photon upconversion

Abstract

Nobuo Kimizuka, "Kinetically controlled crystal growth approach to enhance triplet energy migration-based photon upconversion," J. Photon. Energy 8(2), 022003 (2017), doi: 10.1117/1.JPE.8.022003. Abstract. Improving efficiency of triplet-triplet annihilation-based photon upconversion (TTA-UC) in crystalline media is challenging because it usually suffers from the severe aggregation of the donor (sensitizer) molecules in acceptor (emitter) crystals. We show a kinetically controlled crystal growth approach to improve donor dispersibility in acceptor crystals. As the donor-acceptor combination, a benchmark pair of platinum(II) octaethylporphyrin (PtOEP) and 9,10-diphenylanthracene (DPA) is employed. A surfactant-assisted reprecipitation technique is employed, where the concentration of the injected PtOEP-DPA solution holds the key to control dispersibility; at a higher PtOEP-DPA concentration, a rapid crystal growth results in better dispersibility of PtOEP molecules in DPA crystals. The improvement of donor dispersibility significantly enhances the TTA-UC quantum yield. Thus, the inherent function of donor-doped acceptor crystals can be maximized by controlling the crystallization kinetics.

van der Waals solid solution crystals for highly efficient in-air photon upconversion under subsolar irradiance

“…After some initial work, [23][24][25][26][27][28] the major obstacle has been segregation of the sensitizer from the condensed phase of the annihilator, [29][30][31][32][33][34][35][36][37][38] which forms an aggregate of the sensitizer and greatly diminishes the UC quantum yield ( UC, defined as a maximum of 50% in this report), as typically reported for the combination of platinum octaethylporphyrin (PtOEP, Fig. 1b) and 9,10-diphenylanthracene (DPA, Fig.…”

“…1b). [29][30][31][32][33] To avoid this segregation issue, previous works used a kinetically controlled approach [30][31][32][33][34][35][36][37][38] where organic solids were quickly formed. For example, Simon and coworkers 30 reported molecular glasses by rapidly cooling a hot melt of a sensitizer annihilator mixture, but suppression of the aggregate was incomplete.…”

“…For example, Simon and coworkers 30 reported molecular glasses by rapidly cooling a hot melt of a sensitizer annihilator mixture, but suppression of the aggregate was incomplete. Other works [31][32][33][34][35][36][37][38] formed organic thin films by casting a solvent solution on a flat substrate, where researchers, to an effective extent, suppressed the segregation of the sensitizer from the annihilator chromophores.…”

Strategies for High‐Performance Solid‐State Triplet–Triplet‐Annihilation‐Based Photon Upconversion

“…To our knowledge, this is the first demonstration of a completely dry-processed solid-state TTA upconversion system having comparable performance to solution-processed solid-state systems. [13,14,23,[35][36][37][38] Further improvements could be realized by choosing materials with longer triplet diffusion length as sensitizer, employing a buffer material that enables efficient triplet transfer and blocks back transfer without undergoing upconversion itself, This article is protected by copyright. All rights reserved.…”

Molecular doped organic semiconductor crystals for optoelectronic device applications

“…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.…”