COMPARATIVE CHARACTERISTICS OF MOCVD ZNO AND SPUTTERED ZNO FILMS AND THEIR APPLICATIONS IN N-I-P FLEXIBLE THIN FILM SILICON SOLAR CELLS

摘要

We have prepared zinc oxide (ZnO) films by using two techniques, metalorganic chemical vapor deposition (MOCVD) and DC magnetron sputtering, and comparatively investigated properties of the films. Electrical resistivity of the ZnO films deposited by both techniques was found to be nearly the same, i.e. 1.0~6.0 × 10~(-3) ohm cm. Bandgap of the MOCVD ZnO was estimated to be about 3.3 eV while that of the sputtered ZnO was 3.6 eV. The sputtered ZnO films had relatively smooth surface, whereas the MOCVD ZnO films showed tetrapodlike morphology and their gain size varied with B_2H_6 flow rate. We applied the MOCVD ZnO as a back reflector and the sputtered ZnO as a front electrode of n-i-p amorphous silicon solar cells using polyimide substrate. Quantum efficiency (QE) results indicated that the thickness of the MOCVD ZnO back reflector affected light scattering at the back side, leading to a change in cell performance. Our flexible silicon solar cell showed initial conversion efficiency of 4.3% (active area 2.5 cm~2).