Effect of ZnO deposition condition for back reflector on the performance of nano-crystalline silicon solar cell

We have deposited ZnO at different substrate temperatures in a range of 120 ∼ 350 °C for back reflector (BR) with a structure of ZnO/Ag/Al/SS used in nano-crystalline silicon solar cells. AFM, XRD, SEM and optical transmittance have been employed to analyze the structure of ZnO films. It is found that the nano-crystalline solar cells on the back reflector with ZnO film deposited at 120 °C have a lower fill factor (FF) and a lower short-circuit current density (Jsc), but a higher open-circuit voltage (Voc). This may be caused by the high fraction of amorphous phase in the nano-crystalline silicon film, which grows on the low temperature deposited ZnO film. But when the ZnO deposition temperature is increased to 280 °C, the nano-crystalline silicon solar cells have a lower yield. The reason for this is the formation of a large amount of ZnO nano-crystalline rods on ZnO surface. The optimized BR has contributed to the development of high efficient a-Si:H/a-SiGe:H/nc-Si:H n-i-p triple solar cells with an efficiency of 12.5%.