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Performance of ITO-free inverted organic bulk heterojunction photodetectors: Comparison with standard device architecture

: Arredondo, B.; Dios C. de; Vergaz, R.; Criado, A.R.; Romero, B.; Zimmermann, B.; Würfel, U.


Organic Electronics 14 (2013), Nr.10, S.2484-2490
ISSN: 1566-1199
Fraunhofer ISE ()
Solarzellen - Entwicklung und Charakterisierung; Farbstoff; Organische und Neuartige Solarzellen; Alternative Photovoltaik-Technologien; Organische Solarzellen; Farbstoff- und Organische Solarzellen; Photodetector; Structure; ITO-free

We report on the fabrication of Indium Tin Oxide (ITO)-free inverted organic bulk heterojunction (BHJ) photodetectors of poly(3-hexylthiophene) (P3HT): 1-(3-methoxycarbonyl)-propyl-1-1-phenyl-(6,6) C61 (PCBM). The final inverted device structure is Cr/Al/Cr/P3HT:PCBM/poly-3,4-ethylenedioxythiophene:poly-styrenesulfonate (PEDOT:PSS)/Ag (Zimmermann et al., 2009). The device is top-absorbing with the light entering through the hole contact grid. We have fabricated standard devices with structure ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al in order to carry out a comparison study. Inverted photodetectors show slightly higher quantum efficiency and responsivity compared to standard devices. Frequency responses at different bias voltages were measured showing a maximum -3 dB cut-off frequency of 780 kHz and 700 kHz at -3 V for the standard and inverted structures respectively. Parameters extracted from the fit of a circuital model to the impedance spectroscopy measurements were used to estimate the photodiode cut-off frequency as function of bias.