Dresden 2020 – wissenschaftliches Programm
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CPP 9.7: Vortrag
Montag, 16. März 2020, 11:30–11:45, POT 112
High-gap donor-acceptor blends exhibiting both efficient emission and charge-generating properties — •Xiangkun Jia1, Sascha Ullbrich1, Johannes Benduhn1, Vasileios C. Nikolis1, Jinhan Wu1, Yuan Liu1, Axel Fischer1, Donato Spoltore1, Sebastian Reineke1, and Koen Vandewal1,2 — 1Technische Universität Dresden, Dresden, Germany — 2Hasselt University, Hasselt, Belgium
We demonstrate that the intermolecular charge-transfer (CT) states at the donor-acceptor interfaces are crucial for the operation of organic optoelectronics. Such D-A based OLEDs show electroluminescence external quantum yields (EQEEL) of up to 16%, while in contrast, D-A systems for state-of-the-art OSCs typically only feature EQEEL ≈ 0.01−0.0001%. The dominating non-radiative recombination in the latter is the main reason for their large voltage losses and low power-conversion efficiencies. Here, we adopt high-gap materials to increase the energy of CT states. This blend shows a fill factor of 70% and an internal quantum efficiency of 83% upon solar illumination, comparable to well performing OCSs. Meanwhile, its non-radiative voltage loss is reduced to 0.10 V and EQEEL reaches 1.5%. This work therefore shows that efficient photogeneration of free carriers and a high electroluminescence quantum yield do not necessarily need to be mutually exclusive in organic semiconductors.