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Title:	The effect of wet chemical treatment on ZnO nanorod arrays for inverted organic solar cell applications
Authors:	Abdelelah Ali Ghathwan Alshanableh (P64770)
Supervisor:	Yap Chi Chin, Assoc. Prof. Dr.
Keywords:	Wet chemical ZnO nanorod Universiti Kebangsaan Malaysia -- Dissertations
Issue Date:	27-Oct-2017
Description:	The power conversion efficiency (PCE) of inverted organic solar cells (IOSCs) based on ZnO nanorod arrays is limited by relatively small interfacial area between the polymer donor and ZnO acceptor for efficient exciton dissociation. Wet chemical treatment can be applied on ZnO nanorod to produce hollow structure with increased surface area. However, more defects on the ZnO surface might be created as well, which subsequently cause higher charge carrier recombination rate. The main objective of this study is to determine the effects of various wet chemical treatments on the properties of ZnO nanorod arrays and the subsequent photovoltaic performance. Three different wet chemical treatments, namely chemical treatment, internal self-etching, and combination of both chemical treatments were investigated. ZnO nanorod arrays were prepared on ZnO nanoparticles-seeded fluorine tin oxide (FTO) substrates by using a hydrothermal technique. Chemical treatment was applied on the ZnO nanorods using potassium hydroxide (KOH) at concentrations of 1.0 mM and 0.1 M, as well as hydrochloride acid (HCl) at a concentration of 1.0 mM at 75oC for 70 min inside an oven. Meanwhile, internal self-etching was applied at room temperature for different durations of 35, 70, and 105 min. The same chemical treatment was then applied on the sample treated for 35 min. To investigate the photovoltaic performance, the wet chemical-treated ZnO nanorods were applied as acceptor in IOSCs with a configuration of FTO/ZnO/P3HT/Ag. As expected, the chemical treatment was unable to create hollow structure of ZnO nanorods. Surprisingly, the HCl treatment managed to reduce the oxygen defects of ZnO as indicated by the photoluminescence measurement. It is interesting to find that the ZnO nanorods undergoing internal selfetching for 35 min exhibited the highest defects. In addition, the ZnO nanorods underwent deformation twining with longer treatment time (70 and 105 min), resulting in formation of partially hollow twin ZnO nanorods. By applying the chemical treatment on the sample treated for 35 min which had the highest defect, partially hollow ZnO nanorods were successfully obtained by using 0.1 M KOH. The IOSCs based on ZnO treated with chemical treatment using HCl exhibited a PCE of 0.24 %, which is higher than that treated with KOH (0.17 %), due to the efficient passivation of surface defect under HCl treatment. Both IOSCs exhibited significant higher PCE as compared to that based on pristine ZnO (0.09%). The best photovoltaic performance was achieved with a combined chemical treatment (35 min internal self-etching treatment and 0.1 M KOH chemical treatment), in which the device showed a short circuit current density of 1.43 mA.cm-2, an open circuit voltage of 0.47 V, a fill factor of 48.7% and PCE of 0.32%. It is suggested that the improvement is due to the improved interfacial area and reduced surface defect. In conclusion, combination of internal self-etching and chemical treatment has been proven to be a valuable approach in the improving the performance of IOSCs.,Certification of Master's/Doctoral Thesis" is not available
Pages:	122
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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