Activation of TADF in Photon Upconverting Crystals of Dinuclear Cu(I)-Iodide Complexes by Ligand Engineering
Joy Chatterjee, Abhijit Chatterjee, Riteeka Tanwar, Prakash Panwaria, Sajid Saikia, Madan D. Ambhore, Pankaj Mandal, Partha Hazra
Abstract
This work reports that ligand engineering can modulate the triplet harvesting mechanism in iodide-bridged rhombic Cu 2 I 2 complexes. Complex-1, with a smaller Cu–Cu distance, exhibits phosphorescence from 3 (M+X)LCT and 3 CC states with 66% quantum yield, whereas an increased Cu–Cu distance in complex-2 results in a switch of the emission from phosphorescence to TADF, which occurs via 1/3 (M+X)LCT states with 83% quantum yield. The TADF property of complex-2 has been utilized for the fabrication of a pc-LED emitting efficient warm white light. Moreover, the high charge-transfer nature of these complexes leads to the emergence of third-harmonic generation (THG). Interestingly, complex-1 exhibits efficient third-harmonic generation with a χ (3) value of 1.15 × 10 –18 m 2 V –2 and LIDT value of 14.73 GW/cm 2 . This work aims to provide a structure–property relationship to achieve effective harvestation of triplet excitons in iodide-bridged rhombic Cu 2 I 2 complexes and their effective utilization in OLED device fabrication and nonlinear photon upconversion processes.