AC module based on stacked a-Si-alloy and c-Si solar cells: design, technology and performance evaluation

Multibandgap photovoltaic conversion is applied to PV modules: the proposed device consists of a semitransparent a-Si module and a c-Si module in a stacked configuration. Solar cells in every layer of the stack are series connected according to the commonly used integration techniques giving rise to two independent circuits, driving specific peak power trackers. A two-stage module inverter provides a single AC output line. The whole structure glass/TCO/p-i-n(a-Si alloy)/TCO/sealing polymer/n-p(c-Si)/Ag is simulated taking into account experimental optical and transport parameters of a-Si alloys in a wide range of compositions. It is shown that a proper design of the device should allow efficiency improvements larger than 20% with respect to c-Si solar cells used in the bottom layer. Cost-benefits analysis is also performed, pointing out that no cost increase is expected (in $/W) for the stacked modules, with respect to common c-Si modules