The quest for very high efficiency in Photovoltaic energy conversion

Abstract

ike any conversion system of energy, a photovoltaic generator has its performances limited by the laws of thermodynamics. In a first approach, one can regard the sun as a hot source with T = 6000 K, the cold source being the environment (T e~3 00 K). e Carnot efficiency of the solar energy conversion is 95 % in theory! However, today's best photovoltaic devices, semiconductor photodiodes, achieve efficiencies of only 20-25 %. e difficulty lies with the optimal conversion of a whole range of photons whose energy goes from the infrared to the ultraviolet, with only one active material whose optical properties can be optimally adapted only to a given photon energy (the

Photovoltaic Conversion: Outlook at the Crossroads Between Technological Challenges and Eco-Strategic Issues

“…The multi-junctions, equipped with solar concentrators with a factor of up to 1000, are by far the most performing, with a record performance of 35.8% announced in 2009. However, the applications remain limited since they are confined to the space and military fields (Chataing, 2009;Guillemoles, 2010). While the performances of the organic cells are lower, from 8% to 12%, interest in such cells and particularly the Grätzel cells is growing since the production costs are constantly declining with an interesting price outlook estimated at $0.73 dollars US (0.5 Euros) per Wc in 2020 (Chabreuil, 2010;EPIA/Greenpeace, 2011).…”