Low Temperature Solution Processing Of ZnO Thin Films And Their Applications For Optoelectronics

Low temperature solution processing technologies have the advantage of low cost and capable of massive production. This work successfully prepared ZnO thin films by low temperature solution processing technologies and applied them in optoelectronic devices.The results are described as following:1. Low-voltage DC electrophoretic deposited ZnO nanocrystal Films:we synthesized ZnO nanocrystals by controllable hydrolysis of zinc acetate in alcobolic solutions at60℃. The colloidal stability and electrophoretic properties of the resulting nanocrystal solutions, with or without additional ligands, were analyzed. The results show that the ZnO nanocrystals with ligands exhibit excellent dispersibility and colloidal stability and are positively charged when dissolved in the mixed solution of methanol and chloroform with a volume ration of4:1. We fabricated ZnO thin films with different thickness by controlling the deposition voltage and deposition time. Raman and XRD characterizations indicated that the thin films had wurtzite structure. SEM and AFM analyses showed that the condensed thin films exhibited smooth surface features. Uv-Vis-NIR measurements suggested that the resulting thin films were highly transparent in the visible range. We fabricated inverted organic solar cell using P3HT:PCBM blends based on the electrophoretic deposited ZnO nanocrystal films. The inverted cells showed a decent power conversion efficiency of4.19%, among which flexibility cells had a power conversion efficiency of3.88%, as good as the cells based on spin coating.2. ZnO thin films prepared from Zn(OH)2(NH3)x ammonia complex precursor: we synthesized Zn(OH)2(NH3)x ammonia complex precursor by low temperature chemical reactions. It has a concentration of0.11M and good stability since the solution are stable at ambient conditions for more than three months. TGA analyses indicated that the Zn(OH)2(NH3)x ammonia complex were converted to ZnO at low temperature(≤150℃). Raman and XRD characterizations indicated that the thin films had wurtzite structure. SEM and AFM analyses showed that the condensed thin films exhibited smooth surface features. Uv-Vis-NIR measurements suggested that the resulting thin films were highly transparent in the visible range. We fabricated inverted organic solar cell using P3HT:PCBM blends based on the ZnO thin films from the Zn(OH)2(NH3)x ammonia complex precursor. The inverted cells showed a decent power conversion efficiency of4.17%. We also fabricated thin film transistors based on ZnO thin films from the Zn(OH)2(NH3)x ammonia complex precursor. The thin film transistor devices exhibit decent performance of a field effect mobility of0.5cm2V-1s-1and an on-off ratio of106.