Elucidating Deviating Temperature Behavior of Organic Light‐Emitting Diodes and Light‐Emitting Electrochemical Cells

• Published in: Advanced Optical Materials 2021-01, Vol.9 (1), p.n/a
• Main Authors: Ràfols‐Ribé, Joan, Gracia‐Espino, Eduardo, Jenatsch, Sandra, Lundberg, Petter, Sandström, Andreas, Tang, Shi, Larsen, Christian, Edman, Ludvig
• Format: Article
• Language: English
• Subjects: doping effects; Electrochemical cells; emission zone position; light-emitting electrochemical cells; Materials science; optical simulation; Optics; Organic light emitting diodes; Organic semiconductors; Super Yellow; Temperature dependence
• ISSN: 2195-1071; 2162-7568; 2195-1071
• DOI: 10.1002/adom.202001405

Organic light‐emitting diodes (OLEDs) and light‐emitting electrochemical cells (LECs) exhibit different operational modes that render them attractive for complementary applications, but their dependency on the device temperature has not been systematically compared. Here, the effects of a carefully controlled device temperature on the performance of OLEDs and LECs based on two common emissive organic semiconductors are investigated. It is found that the peak luminance and current efficacy of the two OLEDs are relatively temperature independent, whereas, the corresponding LECs exhibit a significant increase by ≈85% when the temperature is changed from 20 to 80 °C. A combination of simulations and measurements reveal that this deviating behavior is consistent with a shift of the emission zone from closer to the transparent anode toward the center of the active material for both the OLEDs and the LECs, which in turn can be induced by a stronger positive temperature dependence of the mobility of the holes than the electrons. The temperature behavior of two common organic light‐emitting diodes and light‐emitting electrochemical cells differs in that the emission efficiency of the former is independent of temperature, whereas the efficiency of the latter, unexpectedly, increases significantly. This deviating behavior is rationalized with a similar temperature‐induced migration of the emission zone from closer to the anode towards the center of the device.