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HL: Fachverband Halbleiterphysik

HL 25: Focus Session: Young Semiconductor Forum

HL 25.5: Hauptvortrag

Mittwoch, 11. März 2026, 11:45–12:15, POT/0251

How to achieve high gain in organic photodetectors? — •Johannes Benduhn — Institute of Applied Physics, TU Dresden, Germany — German Centre for Astrophysics, Görlitz, Germany

Organic photodetectors (OPDs) match their inorganic counterparts in performance, with additional features like semitransparency, flexibility, and narrowband detection, opening new sensing applications. However, high-gain OPDs are challenging due to disorder. This work discusses two alternative principles to achieve gain.
The first approach uses unbalanced charge-carrier transport. Photo-generated charges accumulated near one of the contacts generate a local field that triggers charge injection of charges from the external circuit into the active layer. Under dark conditions, this injection is absent; therefore, these devices reach impressive EQE values of 1,000-10,000 %. However, the underlying microscopic mechanisms remain unclear. Here, we precisely tune the interface layers via vacuum deposition, enabling us to reveal the injection mechanism.
Another solution is photoactive transistors. We introduce vertical organic-permeable base transistors (OPBTs) that operate at low driving voltages and achieve high switching speeds. We report, for the first time, a photogating effect in OPBTs. By leveraging the unique structure of OPBTs and conducting a detailed investigation into the underlying charge-storing mechanism, we have achieved record responsivity values reaching 10⁹ A/W, specific detectivities of 10¹⁵ Jones (based on noise measurements), and retention times exceeding 10⁵ s. [1]
[1] Schröder, Benduhn et al. Nature Photonics 19, 1088-1098 (2025).

Keywords: organic semiconductors; photodetectors; phototransistors; photogain