Efficiency of Polymer Light-Emitting Diodes: A Perspective.

Autor: Van der Zee B; Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany., Li Y; Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany., Wetzelaer GAH; Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany., Blom PWM; Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany.
Jazyk: angličtina
Zdroj: Advanced materials (Deerfield Beach, Fla.) [Adv Mater] 2022 Apr; Vol. 34 (13), pp. e2108887. Date of Electronic Publication: 2022 Feb 11.
DOI: 10.1002/adma.202108887
Abstrakt: The various contributions to the external quantum efficiency (EQE) of polymer light-emitting diodes (PLEDs) are discussed. The EQE of an organic light-emitting diode is governed by a number of parameters, such as the electrical efficiency, the photoluminescence quantum yield (PLQY), the optical outcoupling efficiency and the spin statistics for singlet exciton generation. In the last decade, the electrical efficiency has been determined from a numerical PLED device model. More recently, an optical model to simulate the fraction of photons outcoupled to air for PLEDs with a broad recombination zone has been developed. Together with the directly measured PLQY, the EQE of a PLED can then be estimated. However, it has been observed that the measured EQEs of fluorescent PLEDs, including the model system super-yellow poly(p-phenylene vinylene) (SY-PPV) often exceed the expected values. To solve this discrepancy, it is demonstrate that the electrical PLED model has to be expanded by the inclusion of triplet-triplet annihilation (TTA), which is shown to be responsible for a substantial EQE enhancement. Experimentally, it is obtained that TTA contributes to a singlet-exciton generation efficiency of ≈40% in SY-PPV PLEDs, giving rise to an EQE of ≈4% instead of the expected value of 2.5%.
(© 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH.)
Databáze: MEDLINE
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