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    Effects of PEDOT:PSS and crystal violet interface layers on current-voltage performance of Schottky barrier diodes as a function of temperature and variation of diode capacitance with frequency
    (Elsevier, 2022) Deniz, A. R.; Tas, A. I.; Caldiran, Z.; Incekara, U.; Biber, M.; Aydogan, S.; Turut, A.
    In this study, diode applications of Crystal Violet (CV) and PEDOT materials were studied. The Ni/p-Si/Al, Ni/CV/p-Si/Al and Ni/PEDOT:PSS/CV/p-Si/Al diodes were fabricated. The I-V (current-voltage) characteristics of all diodes were analyzed at room temperature, it was determined that the PEDOT:PSS and CV materials improved the basic diode parameters. Also, I-V characteristics of Ni/PEDOT:PSS/CV/p-Si/Al of diode were investigated for different temperature values. It has been determined that the basic diode parameters are strongly dependent on temperature. It was determined that while the barrier height (Fb) increased with increasing temperature, the ideality factor (n) and the series resistance (Rs) values decreased. Using temperature-dependent measurements, it was determined that the potential barrier and ideality factor values at the contact interface has a double Gaussian distribution. In addition, C-V (capacitance-voltage) measurements of these diodes were analyzed depending on the frequency. It was found that the diode capacitance decreased with increasing frequency.
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    Effects of the PENTACENE as doping material on the power conversion efficiency of P3HT:PCBM based ternary organic solar cells
    (Elsevier, 2021) Caldiran, Z.; Erkem, U.; Baltakesmez, A.; Biber, M.
    In organic solar cells (OSCs), changing the device geometry and the photophysical properties of the active layer is an effective way to change the power conversion efficiency (PCE). For this purpose, both the buffer layer was coated between the active layer and the metal and the organic material was doped to the active layer to obtain the ternary structure. In this study, for the fabrication of bulk-heterojunction (BHJ) organic solar cell, the PEDOT:PSS layer was coated on chemically cleaned ITO coated glass substrates by the spin coating method. Subsequently, the P3HT:PCBM blend as an active layer was coated on top of PEDOT:PSS in the glove box using the same method. Finally, aluminum (Al) was coated using thermal evaporation and ITO/PEDOT:PSS/P3HT: PCBM/Al organic solar cells structure as reference device were obtained. Then, PENTACENE material with an organic semiconductor property was doped into P3HT:PCBM blend and ITO/PEDOT:PSS/P3HT:PCBM:PENTACENE/Al bulk heterojunction organic solar cell structure was obtained using the same method. In addition, the effects of OSC on PCE were investigated by coating the 2 nm lithium fluoride layer between the Al and the active layer. For devices, dark and light current density-voltage (J-V) measurements were performed under 100 mW/ cm2 in the glove box, and device parameters were calculated by the J-V curve. It was observed that the reference device showed photovoltaic properties under light and its PCE was 0.64%. When the experimental findings obtained were examined, both the LiF buffer layer and PENTACENE doping material improved the ternary OSC device performance and increased the PCE from 0.64% to 2.65%, according to the reference device. As a result of the doping, the mobility of the carrier increased with the increase of photon absorption and the presence of the buffer layer increased the carrier injection. Changing device properties can be explained with these results.