Preparation Of Fluorine Doped ZnO Transpaent Conductive Thin Films And Their Application In Solar Cells

Zinc oxide (ZnO) transparent conductive thin films, with unique electrical and optical properties, have been used extensively in thin film solar cells, light-emitting diodes, flat panel displays and various optoelectronic devices. Most of the previous studies were carried out with metallic cation dopants such as B, Al, Mn, Ga, and In, however, fluorine can be a promising n-type anion doping candidate. In this paper, we prepared F-doped ZnO thin films to carry out some investigation. Besides, the films were applied as the front contact for single junction amorphous silicon p-i-n solar cells to verificate the properties. The main work contains:1. F-doped ZnO thin films were prepared on PC substrates by RF magnetron sputtering at room temperature to investigate the effect of different sputtering parameters on these films. Lowest resistivity of 7.66×10-2 Ωcm, with carrier concentration of 1.31×1020 cm-3 and Hall mobility of 0.62 cm2V-1s-1, was achieved at 0.3Pa. Importantly, an average optical transmittance of above 80% was achieved for all doped films in the spectrum range of 300～2000 nm. With a ZnO buffer layer, the electrical resistivity of FZO/ZnO/PC films reduced to 5.82×10-3Ωcm with hall mobility improved from 0.618 cm2 V-1s-1 to 8.08 cm2 V-1s-1, as the crystal quality was significantly improved.2. A chemical solution etching combined A1/H2 plasma etching method is used to fabricate the textured surface of RF-sputtered ZnO:F (FZO) transparent conductive films. To achieve good cell performance, the surface morphology varies adequately by this two-etching method. The crystalline quality improved slightly with the increase of H2. A minimum resistivity value of 1.135×10-3 Ωcm with carrier concentration of 2.854×1020 cm-3 and Hall mobility of 19.29 cm2V-1s-1 are obtained.The enhanced optical scattering reflectance of the textured surface presents a best haze value of 52.14% at the wavelength of 550 nm. Using the optimized plasma-etched FZO film as the front contact layer of the preliminary amorphous silicon solar cells, conversion efficiency up to 4.0% is achieved, which is much higher than that of the none-plasma-etched FZO film based device (1.0%).