Photovoltaic generation has stepped up within the last decade from outsider status to one of the important contributors of the ongoing energy transition, with about 1.7% of world electricity provided by solar cells. Progress in materials and production processes has played an important part in this development. Yet, there are many challenges before photovoltaics could provide clean, abundant, and cheap energy. Here, we review this research direction, with a focus on the results obtained within a Japan–French cooperation program, NextPV, working on promising solar cell technologies. The cooperation was focused on efficient photovoltaic devices, such as multijunction, ultrathin, intermediate band, and hot-carrier solar cells, and on printable solar cell materials such as colloidal quantum dots.

This paper presents the low cost electrodeposition of a transparent and conductive chlorine doped ZnO layer with performances comparable to that produced by standard vacuum processes. First, an in-depth study of the defect physics by ab-initio calculation shows that chlorine is one of the best candidates to dope the ZnO. This result is experimentally confirmed by a complete optical analysis of the ZnO layer deposited in a chloride rich solution. We demonstrate that high doping levels (>1020 cm−3) and mobilities (up to 20 cm2 V−1 s−1) can be reached by insertion of chlorine in the lattice. The process developed in this study has been applied on a CdS/Cu(In,Ga)(Se,S)2 p-n junction produced in a pilot line by a non vacuum process, to be tested as solar cell front contact deposition method. As a result efficiency of 14.3% has been reached opening the way of atmospheric production of Cu(In,Ga)(Se,S)2 solar cell.

We develop a model to predict the performances of microscale Cu͑In, Ga͒Se 2 ͑CIGS͒ solar cells under concentrated sunlight, based on the study of the influence of the window spread sheet resistance, which is the first limiting factor for concentration on CIGS solar cells. This model can be used to extract the value of the sheet resistance from simple current-voltage or electroluminescence measurements. The scaling benefits associated with the operation of microscale CIGS solar cells are studied. The optimum concentration ratio, linked to the best efficiency, is calculated for different cell sizes. It is predicted that an increase from 20% efficiency, for current CIGS solar cells under 1 sun illumination, up to 30% efficiency can be expected for microscale cells under concentrated sunlight.