Optical and Electrical Characterization of a ZnO/Coronene-Based Hybrid Heterojunction Photodiode

Metal oxide hexagonal ZnO thin film with thickness of approximately 509 nm was successfully grown on a glass/ITO substrate by electrochemical deposition. It was observed that Zn and O were homogeneously distributed in the thin film and crystals formed in the (100), (002), (101), (102) and (201) planes. The ZnO surface morphology was characterized by cauliflower-like structures which were composed of nanorods. Coronene organic semiconductor nanowire (similar to 503 nm thick) was deposited on glass/ITO/ZnO by a physical vapor deposition technique. Additionally, UV-Vis spectrometry measurements revealed that the maximum absorption value of the heterojunction was observed at the near-ultraviolet region, and the maximum absorption coefficient (alpha) value was determined to be 3.55 x 10(6) m(-1). Also, the bandgap (E-g) value of the heterojunction was 3.24 eV. After Ag metal contacts were grown on ZnO and coronene surfaces, electrical characterization of the Ag/ZnO/coronene/Ag heterojunction was performed in the dark and under 20 mW cm(-2) light intensity. The electrical analysis indicated that the diode ideality factor (n), series resistance (R-s), and barrier height (empty set(b)) values of the Ag/ZnO/coronene/Ag hybrid heterojunction decreased under illumination, while the reverse saturation current (I-0) value increased. The photocurrent (I-ph), photoresponsivity (R) and photosensitivity (S) of the heterojunction were determined at 20 mW cm(-2) light intensity under reverse and forward bias, and values of 3.73 x 10(-5) A, 0.23 A W-1 and 5.47 x 10(-8) S m W-1 were obtained, respectively. In addition, the photovoltaic parameters of the heterojunction were examined, and short-circuit current (I-sc), maximum power point current (I-m(pp)), open-circuit voltage (V-oc), maximum power point voltage (V-mpp) and fill factor (FF%) values of 1.41 x 10(-6) A, 8.76 x 10(-7) A, 0.06 V, 0.03 V and 31% were observed, respectively. These findings indicate that the fabricated heterojunction is highly photoresponsive and shows photodiode and photovoltaic properties.