Revealing the Impact of Heat Generation Using Nanographene-Based Light-Emitting Electrochemical Cells

• DOI: 10.1021/acsami.0c06783
• Publication Date: 2020-06-01T11:21:41Z
• Authors: Elisa Fresta; Jacopo Dosso; Juan Cabanillas-G...; Davide Bonifazi; Rubén D. Costa
• Keywords: 205019 Material sciences; nanographene; nanographenes; DEVICES; device efficiency; light-emitting electrochemical cells; nanographenes; self-heating; small molecules; 210006 Nanotechnology; EFFICIENT; light-emitting electrochemical cells; 7. Clean energy; 01 natural sciences; light-emitting electrochemical cell; ELECTROLUMINESCENCE; TEMPERATURE; device efficiency; 205019 Materialwissenschaften; COMPLEX; ORIGIN; self-heating; 0104 chemical sciences; small molecules; 210006 Nanotechnologie; HOST MATERIALS; WHITE; EMISSION

Self-heating in light-emitting electrochemical cells (LECs) has been long overlooked, while it has a significant impact on (i) device chromaticity by changing the electroluminescent band shape, (ii) device efficiency because of thermal quenching and exciton dissociation reducing the external quantum efficiency (EQE), and (iii) device stability because of thermal degradation of excitons and eliminate doped species, phase separation, and collapse of the intrinsic emitting zone. Herein, we reveal, for the first time, a direct relationship between self-heating and the early changes in the device chromaticity as well as the magnitude of the error comparing theoretical/experimental EQEs-that is, an overestimation error of ca. 35% at usual pixel working temperatures of around 50 °C. This has been realized in LECs using a benchmark nanographene-that is, a substituted hexa-peri-hexabenzocoronene-as an emerging class of emitters with outstanding device performance compared to the prior art of small-molecule LECs-for example, luminances of 345 cd/m2 and EQEs of 0.35%. As such, this work is a fundamental contribution highlighting how self-heating is a critical limitation toward the optimization and wide use of LECs.