New silicon thin-film technology associated with original DC-DC converter: An economic alternative way to improve photovoltaic systems efficiencies

In this article, we aim at optimizing an innovative tandem structure based on polymorphous and microcrystalline silicon for the top and bottom elementary cells, respectively, combined with an original DC-DC converter. The studied tandem structure is composed of two cells, each being connected to its own separate electrodes making the structure electrically decoupled but optically coupled. In those conditions, the constraint of current matching usually needed in the classical micromorph structures is avoided. As a result, the robustness against the current variations is enhanced and the efficiency of the structure is improved. Since the top cell plays the main role in the determination of the transmitted part of the incoming flux to the bottom cell, the thickness of the intrinsic layer of the polymorphous cell is tuned so that the output power of the global structure becomes maximal. To implement the electric decoupling of two sub cells, the studied structure needs two static converters. In order to minimize the converters bulk, we design an innovative output electric architecture and its optimized related control signals. -- Highlights: → We optimized an innovative silicon thin film 4-wires tandem solar structure. → The sub-cells are made of polymorphous and microcrystalline silicon. → Electric decoupling of solar sub-cells leads to avoid current matching constraint. Robustness against current variations is enhanced and the efficiency is improved. The studied structure is combined with an original DC-DC converter. → This systemic approach improves efficiency and reduces cost of the global structure.