Large Area DC Sputtered Zinc Oxide Front TCO for a-Si / µc-Si Tandem Modules

25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain; 3174-3176
We report on Sunfilm’s recent development of ZnO:Al layers for front contact TCO in a-Si/μc-Si tandem modules. Our new process allows to produce ZnO:Al layers of excellent optical and electrical properties on 1.78 m2 float glass substrates in an industrial DC sputter line. After etching in diluted hydrochloride acid, the TCO exhibits haze values > 60 % at 700 nm and a surface texture tailored for a-Si/μc-Si tandem modules. TCO with such properties is usually obtained using lab scale RF sputter processes only, which, however, have too low deposition rates and are difficult to scale to large areas for industrial application. On the new TCO substrates a-Si/μc-Si tandem modules with a stabilized total area efficiency of 8.3 % have been produced at Sunfilm. This is comparable to our typical module performance on commercial SnO2:F based TCO substrates.