Research database

CLAIRE - Clean LArge-scale energy harnessing with perovskite/silicon three terminal heterojunction bIpolar tRansistor solar cElls

24 months (2025)
Principal investigator(s):
Project type:
Nationally funded research - PRIN
Funding body:
MINISTERO (Ministero dell'Università e della Ricerca)
Project identification number:
PoliTo role:


Silicon photovoltaics (PV) cover about 90% of today PV market with record efficiency cells close to their theoretical limit of 30%. Perovskite (PVK) / Si tandem extends this limit up to 42% and is one of the more fast advancing and promising technologies to ensure competitiveness and sustainability of PV. High-efficiency and low-cost clean PV energy enabled by PVK/Si technology will be pivotal to reach the zero climate impact goal set by the United Nations and Europe by 2050 and to increase the European energy independence, in particular in countries like Italy with high PV potential owing to its favorable geographical position. Two and four terminal PVK/Si tandems (2T and 4T) are the most investigated, with demonstrated efficiencies up to 29.8% on heterojunction Si cells, but suffer from sub-optimal energy yield due to the series connection (2T) and complex manufacturing at device/module level (4T). The CLAIRE project proposes a novel monolithic architecture for PVK/Si cells based on the heterojunction bipolar transistor (HBT) structure, which brings two striking advantages: 1) It is an inherently 3 terminal (3T) double junction solar cell with efficiency and resilience to spectral variations equal to the 4T one, hence providing the highest possible energy yield in any location. 2) It avoids the use of recombination layers, maximizing the light harvesting and, above all, minimizing shunts when upscaling to large areas. Differently from other 3T solutions proposed so far, the CLAIRE tandem relies on the most common Si PV technologies that will largely dominate the PV market in the next tens of years, hence maximizing the exploitation potential. CLAIRE will prove the feasibility of the HBT PVK/Si architecture with small-area prototypes on planar and textured Si substrates, with a net efficiency gain of at least 5% over the Si baseline cell, and will demonstrate the upscaling of the technology to large areas. In particular, the project will test new deposition techniques on textured Si substrates, developing an innovative close space sublimation process as a scalable deposition method for the perovskite layer. The project brings together two research teams from Politecnico di Torino and Università di Roma Tor Vergata with a strong background on solar cell technology and extensive experience in international projects. CLAIRE enjoys the in-kind participation of ENEA (Italian Agency for new technologies, energy, and sustainable development) and ENEL-3SUN. ENEA will provide customized Si-homojunctions for the development of small-area demonstrators, and ENEL-3SUN will provide bifacial Si HTJ cells for demonstrating the technology over large area commercial cells. With its simplicity and cost-effectiveness, the CLAIRE 3T HBT PVK/Si tandem can make a high impact in the PV field providing a new architecture to go well beyond the 30% limit of single gap solar cells and building upon the existing industrial PV chain for rapid exploitation.





ERC sectors

PE7_5 - (Micro and nano) electronic, optoelectronic and photonic components

Sustainable Development Goals

Obiettivo 7. Assicurare a tutti l’accesso a sistemi di energia economici, affidabili, sostenibili e moderni


Total cost: € 219,213.00
Total contribution: € 199,911.00
PoliTo total cost: € 90,193.00
PoliTo contribution: € 70,891.00