Uniform growth of a-Si / μc-Si Tandem junction solar cells over 5.7m2 substrates

The cost of photovoltaic (PV) energy generation has been steadily reduced with the increase of solar cell power conversion efficiency and the drop of manufacturing cost. An effective way of lowering the cost of Si thin film solar cells is to increase the solar panel size by growing thin films on large area substrates, where it is important to maintain uniform film properties to ensure efficient and consistent PV performance. In this study, we control the thickness and crystalline volume fraction uniformities of Si films grown on 5.7 m² glass substrates in ratio-frequency (RF) plasma enhanced chemical vapor deposition (PECVD) chambers by balancing the RF power distribution. Crystalline volume fraction uniformity of 3% was obtained in μc-Si:H films. Tandem junction (TJ) solar cells of the structure glass/SnO₂:F/a-Si:H/μc-Si:H/ZnO:Al/Ag were grown with the balanced RF feed. With the uniform film deposition, the 5.7 m² solar panels achieved stabilized aperture efficiency η ≫ 8%.