Regensburg 2022 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 28: Organic Semiconductors 1

HL 28.8: Talk

Thursday, September 8, 2022, 11:30–11:45, H34

Exploring the Device Physics of Photomultiplication in Organic Photodetectors — •Louis Conrad Winkler, Jonas Kublitski, Johannes Benduhn, and Karl Leo — TU Dresden, Germany

Recently, photomultiplication (PM) in organic photodetectors has been achieved, but working mechanism and physics are not fully understood. Contrary to inorganic photodiodes, impact ionization and avalanche breakdown cannot be achieved in organic semiconductors. Instead, the accumulation of one charge carrier type close to an electrode leads to a strong energy level bending, which increases the tunnelling probability of the opposite charge carrier type under reverse bias from the metal contact into the device. In this contribution, we investigate the well-known donor-acceptor system ZnPc:C60, using the acceptor as an electron trapping state to inject holes into the donor phase. Since the effective electron mobility is strongly decreased, we investigate whether shifting the generation location influences the device operation, e.g. the response speed and external quantum efficiency. Furthermore, a gradient donor-acceptor mixing ratio is introduced to increase both response speed and free charge carrier generation efficiency via an enlarged donor-acceptor interface. We also investigate the effect of trapping time being larger than the carrier transit time, leading to reduced cut-off frequencies.