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The objective of the BEST-4U project is the fabrication of a photovoltaic cell/module with 4 terminals, having a bifacial Si heterojunction cell as bottom cell and a wide bandgap semiconductor cell as top cell. The bifacial bottom cell collects and converts into electrical energy the red and infrared sunlight, passed through the top cell and, on the backside, the albedo light reflected/scattered from the ground. The top cell collects the blue region of the incident solar spectrum. The objective is an efficiency larger than 25% in standard conditions. Several approaches will be studied and compared with this aim, identifying the more promising. A demonstrator of bifacial photovoltaic field will be also realised, optimized for the ground albedo exploitation with a kWh/kWp productivity larger than 20% compared to the monofacial system. 

To obtain the improvement in the efficiency and productivity we propose the concept of 4 terminals photovoltaic modules. The cells and the 4T modules can be considered as an alternative to the tandem photovoltaic cells, with some advantages. Indeed, the conventional monolithic tandem cell, with 2 cells connected in series, has the limitation of the lattice parameter matching, as well as the current matching. On the contrary, the 4 terminals structure is not affected by these limitations, and  it allows many degrees of freedom.

The BEST-4U Project consortium is coordinated by ENEL GREEN POWER. The other partners are CONSIGLIO NAZIONALE DELLE RICERCHE (CNR), Università  di PERUGIA, Università  di PADOVA, Università  di CATANIA, APPLIED MATERIALS ITALIA SRL, Distretto Tecnologico Sicilia Micro e Nano Sistemi S.c.a.r.l, DTS (with actuators Università  di PALERMO and Italtel S.p.A.), Università  di MILANO-BICOCCA,  Università  di TORINO.

The Project is co-financed by PON Ricerca e Innovazione 2014-2020, under Decreto Direttoriale di concessione dell’agevolazione del 21-05-2019 prot. n. 991, contract code ARS01_00519.

For more information please contact Dr. Salvatore Lombardo


2020-10-15 to 2023-06-30