Issue 23, 2024

Significant differences in photophysical and photovoltaic properties of flexible chain terminated homoleptic tris-Ir(iii) complexes

Abstract

Cyclometallated heavy metal complexes as photoactive materials have not received as much attention as pure organic/polymer counterparts in organic solar cells (OSCs). In this work, a novel homoleptic Ir(III) complex, tris(2-ethylhexyl 5′′-(benzo[d]thiazol-2-yl)-[2,2′:5′,2′′-terthiophene]-5-carboxylate) Ir(III) (ATBz3Ir), is presented for potential use in OSCs. Compared to hexyl-terminated TBz3Ir with the same main ligand backbone, ethylhexyl carboxylic ester-terminated ATBz3Ir exhibits significantly attenuated absorption at longer wavelengths of 400–600 nm. ATBz3Ir only shows phosphorescence peaking at 706 nm with a triplet lifetime of 280 ns in solution, which is dramatically different from the double modal profile for TBz3Ir with high-intensity fluorescence (564 nm/0.59 ns) and low-intensity phosphorescence (790 nm/174 ns). When employed as the third component for PM6:Y6 blended OSCs, ATBz3Ir and TBz3Ir exhibit opposite effects. The maximum power conversion efficiency (PCE) is improved from 15.14% for binary PM6:Y6 to 16.50% for PM6:ATBz3Ir:Y6 based ternary devices, while the PCE decreases to 14.49% for the PM6:TBz3Ir: Y6 device. The main reason could be attributed to the better miscibility between ATBz3Ir and the Y6 acceptor, which induces enhanced Y6-aggregation, and thus increased Y6-absorption, more efficient exciton dissociation, improved electron transport and reduced charge recombination. Similarly, an enhanced PCE was also achieved from 16.11% to 17.04% for other batches of PM6′:Y6′ and from 17.25% to 18.37% for PM6:L8-BO based ternary devices, respectively, which further support the efficiency of the third component of ATBz3Ir.

Graphical abstract: Significant differences in photophysical and photovoltaic properties of flexible chain terminated homoleptic tris-Ir(iii) complexes

Supplementary files

Article information

Article type
Paper
Submitted
18 abr 2024
Accepted
14 mai 2024
First published
15 mai 2024

J. Mater. Chem. C, 2024,12, 8334-8342

Significant differences in photophysical and photovoltaic properties of flexible chain terminated homoleptic tris-Ir(III) complexes

D. You, T. Yang, A. Zhou, S. Li, K. Lv, H. Ma, H. Zhong and Y. Tao, J. Mater. Chem. C, 2024, 12, 8334 DOI: 10.1039/D4TC01588F

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