Examinando por Autor "Vergaz, Ricardo"

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High-bandwidth organic photodetector analyzed by impedance spectroscopy
(IEEE, 2012) Arredondo, Belén; Dios, Cristina de; Vergaz, Ricardo; Pozo, Gonzalo del; Romero, Beatriz
An organic bulk heterojunction photodetector (OPD) is fabricated on the basis of a blend of poly(3-hexyl thiophene):1-(3-methoxycarbonyl)-propyl-1-1-phenyl-(6,6) C61. The OPD responsivity is calculated from current density-voltage characteristic (J-V) under green-LED illumination obtaining 1 A/W. Frequency response at different biases is measured, which shows a high ¿3-dB cutoff frequency of 343 kHz at ¿3 V. Impedance measurements are carried out at different reverse biases, and the results are fitted with a small signal equivalent circuit. The device cutoff frequency (fc) can be estimated with the parameters extracted from this circuit obtaining good agreement between measured and calculated fc.
Performance of ITO-free inverted organic bulk heterojunction photodetectors: Comparison with standard device architecture
(Elsevier, 2013) Arredondo, Belén; Dios, Cristina de; Vergaz, Ricardo; Romero, Beatriz; Zimmermann, Birger; Wurfel, Uli
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) [1]. 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. (C) 2013 Elsevier B.V. All rights reserved.
Visible Light Communication System using an organic bulk heterojunction photodetector
(MDPI AG, 2013) Arredondo, Belén; Romero, Beatriz; Sánchez-Pena, José Manuel; Fernández-Pacheco, Agustin; Alonso, Eduardo; Vergaz, Ricardo; Dios, Cristina de
A visible light communication (VLC) system using an organic bulk heterojunction photodetector (OPD) is presented. The system has been successfully proven indoors with an audio signal. The emitter consists of three commercial high-power white LEDs connected in parallel. The receiver is based on an organic photodetector having as active layer a blend of poly(3-hexylthiophene) (P3HT) and phenyl C61-butyric acid methyl ester (PCBM). The OPD is opto-electrically characterized, showing a responsivity of 0.18 A/W and a modulation response of 790 kHz at -6 V.