A study of ZnO nanorods/Cu2O heterojunction applications to solar cells and to photodetectors with a poly-(N-vinylcarbazole) intermediate layer

  • 洪 敏皓

Student thesis: Doctoral Thesis


In solar cell this study reports the achievement of a high short-circuit current density (Jsc) of 9 53 mA/cm2 for low cost electrodeposited (ED) semi-transparent Cu2O/ZnO nanorod (NR) solar cells High-quality chemicalbath-deposited ZnO NRs that align with the carrier collection path were used to replace the traditionalsputtered ZnO film An almost four-fold increase (from 1 63 to 6 41 mA/cm2) in Jsc was obtained with the NRs compared to the level obtained with a sputtered ZnO thin film cell Decreased the ED Cu2O absorber film thickness is able to compensate for the recombination loss that results from Cu2O's short minority carrier drift and diffusion length (both on the order of 100 nm) further boosting Jsc to 7 77 mA/cm2 Additional photo-generated carriers were created for the semi-transparent solar cells when a silver mirror was deposited on the backside of the glass; this further enhanced absorption and improved Jsc to 9 53 mA/cm2 This is the highest Jsc value reported to date for a low-cost ED Cu2O/ZnO solar cell In photodetector this study reports a high-performance hybrid ultraviolet (UV) photodetector with visible-blind sensitivity fabricated by inserting a poly-(N-vinylcarbazole) (PVK) intermediate layer between lowcost processed Cu2O film and ZnO nanorods (NRs) The PVK layer acts as an electron-blocking/ hole-transporting layer between the n-ZnO and p-Cu2O films The Cu2O/PVK/ZnO NR photodetecto exhibited a responsivity of 13 28 A/W at 360 nm a high detectivity of 1 03×1013 Jones at a low bias of -0 1V under a low UV light intensity of 24 9 μW/cm2 The photo-to-dark current ratios of the photodetector with and without the PVK intermediate layer at a bias of -0 5V are 1 34×102 and 3 99 respectively The UV-to-visible rejection ratios (R360 nm/R450 nm) are 350 and 1 735 respectively Several features are demonstrated: (a) UV photo-generated holes at the ZnO NRs can effectively be transported through the PVK layer to the p-Cu2O layer; (b) the insertion of a PVK buffer layer significantly minimizes the reverse-bias leakage current which leads to a larger amplification of the photocurrent; and (c) the PVK buffer layer greatly improves the UV-to-visible responsivity ratio allowing the device to achieve high UV detection sensitivity at a low bias voltage using a very low light intensity
Date of Award2018 Jul 5
Original languageEnglish
SupervisorDung-Ching Perng (Supervisor)

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