Initial Research And Production Of Large Area CdTe Integrated Solar Cells And Application Contrast Of Different Metal Back Electrode In CdTe Solar Cells

Solar energy photovoltaic technique is one of modern high technical backbones in 21st century, and is one effective approach in solving the conflictions among economy, energy and environment in the world today. Fabrication equipment and corresponding technologies which are fit for cosmical production, for large area CdTe integrated solar cell modules which are capable of action as the independent electrical sources are studied in this paper. In order to find one metal back electrode material which can obtain higher conversion effficiency at obviously lower cost, the effects of different metals on properties of CdTe solar cells are also studied,As initial research and production of large area CdTe integrated solar cell modules, structure designs of vacuum co-operation equipment and annealing equipment for large area ZnTe/ZnTe:Cu complex films, thickness uniformity of and annealing temperature uniformity on the complex films are discussed. New annealing processing is put forward. Integrated modules have been successfully connected from single wafer solar cells by mature fabrication processings of small area CdTe solarcells by use of laser scribing and cover mask. The conversion efficiency of integrated modules can averagely increase 20% by application of ZnTe/ZnTe:Cu complex layers. Up to now, the conversion efficiency of integrated modules has been exceeded 4.5%. But there is still a considerable distance in reaching to the performances of small area CdTe solar cells. Fabrication processings of integrated modules and corresponding physical problems need to be more deeply investigated.Ni could be suitable to the back electrode of CdTe solar cells. Its work function of 5. OeV is a little higher than that of Au(4. 9eV), so it is more easy to form ohmic contact between semiconductor and Ni. It is more improtant that the price of Ni is much lower than that of Au, hence there would be a promising foreground in reducing cost to fit for industrialization.In this paper, the effects and mechanism of Ni and Au back electrode on the performances of CdTe solar cells have been studied experimently. After Ni substituted for Au, junction characteristics of CdTe solar cells without ZnTe/ZnTe:Cu complex layers become bad, diode quality factor A and dark saturation current Jo increases, the shunt resistance Rsh obviously decreases, and the conversion efficiency decreases in different extent. However, for CdTe solar cells with ZnTe/ZnTe:Cu back contact, Ni back electrode only makes the junction characteristics worsen slightly. The copper concentrations and annealing temperatures in complex back contact can match Ni back electrode in a wide range. The conversion efficiency increases, the biggest extent is 30.57%. Because whether there are ZnTe/ZnTe:Cu complex layers or not, the short current of CdTe solar cells with Ni back electrode is higher than that of Au, and the biggest extent is 40. 31%. Our analysis shows that the main cause of short current increasing is the increasing of the light-generated current (JL).As shown from the above, it is not only probable that the conversion efficiencies of cells increase 1% at least, but also it is rather promising to reduce cost in cosmical production.