Regensburg 2022 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 1: Organic Electronics and Photovoltaics 1

CPP 1.12: Talk

Monday, September 5, 2022, 12:45–13:00, H38

Effect of trap states on the performance of organic photodetectors — •Jakob Wolansky¹, Sebastian Hutsch², Felix Talnack¹, Michel Panhans², Jonas Kublitski¹, Stefan Mannsfeld¹, Frank Ortmann², Johannes Benduhn¹, and Karl Leo¹ — ¹Technische Universität Dresden, Dresden, Germany — ²Technische Universität München, Garching b. München, Germany

Due to the broad range of modern applications, the demand for photodetectors is drastically increasing, and in particular, organic photodetectors (OPDs) can meet the diverse requirements. However, the specific detectivity of OPDs is significantly below the thermal limit and is currently restricted by the high noise spectral density. Kublitski et al.[1] recently showed that the shot noise and hence the dark current (JD) dominates the noise spectral density at negative bias. Further, the authors suspect that mid-gap trap states cause the high JD.

Here, we study devices with a well-performing absorber layer without an electron acceptor and, therefore, we do not expect any charge-transfer states to form. Nevertheless, we can observe sub-bandgap absorption in ultra-sensitive external quantum efficiency measurements. By utilizing different device processing parameters and employing different interface layers, we identify the origin of these sub-bandgap excitations. Interestingly, we observe a clear correlation between the device performance and the presence and quantity of trap states. The relation between molecular structure and device performance gives a new direction for reducing JD further in OPDs and improving their specific detectivity. [1] Kublitski, J. et al. Nat Commun 12, 551 (2021)