BEST4U Project

The BEST4U project, acronym of "Bifacial, high efficiency 4-terminals solar cell technology for utility scale", is a PON Research and Innovation 2014-2020 project. The coordinator of the project is ENEL GREEN POWER. It started on 01/04/2020 and ended on 01/04/2023.

The objective of the BEST-4U project was the fabrication of a 4-terminal cell/module, having a bifacial Si heterojunction cell as the bottom cell and a broadband semiconductor cell as the top cell. The double-sided lower cell collects and converts into electrical energy the red and infrared sunlight passed through the upper cell and, on the back, the light reflected and scattered by the ground. The other goal is to achieve an efficiency above 25% under standard conditions. Different approaches have been studied and compared with this goal, identifying the most promising ones. A double-sided photovoltaic field demonstrator has been created, optimized for the exploitation of the ground albedo with a productivity kWh / kWp greater than 20% compared to the single-sided system.

To obtain the improvement of efficiency and productivity it is proposed to use photovoltaic modules with 4 terminals. 4T cells and modules can be considered an alternative to tandem photovoltaic cells, with some advantages. In fact, the conventional monolithic tandem cell, with 2 cells connected in series, has the limitation of lattice parameter matching, as well as current matching. Conversely, the 4-terminal structure is not affected by these limitations and allows many degrees of freedom.

The personnel of the Solar Collectors Laboratory participated in the small-scale field test campaign, optimized for the exploitation of sunlight reflected from the ground.