Dresden 2020 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 5: Organic semiconductors I (joint session HL/CPP)

HL 5.7: Talk

Monday, March 16, 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 Vandewal^1,2 — 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 (EQE_EL) of up to 16%, while in contrast, D-A systems for state-of-the-art OSCs typically only feature EQE_EL ≈ 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 EQE_EL 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.