Inexpensive, efficient solar cells
PV solar cells create electricity from light. Although greatly improved, today's materials still suffer from relatively low efficiency and high cost. The EU-funded NANOCIS (Development of a new generation of CIGS-based solar cells) project established a researcher exchange network to address the issue. Study goals included development of new, low-cost materials promising high efficiencies around 63 %. Research focused on copper indium gallium selenide (CIGS) cells, manufactured by depositing a layer of the semiconductor materials onto either glass or plastic. Such cells offer numerous advantages, including a relatively thin, flexible, yet highly light-absorbing semiconductor film. The project studied the design, manufacture and properties of CIGS and other candidate materials, while testing new concepts in PV conversion to electricity. Using quantum modelling, the team assessed and determined the structure of various new materials sensitive to an intermediate light band. Work also resulted in calculation of the materials' backscatter and other optical properties. Research yielded lists of suitable candidates, and methods of depositing the required layers onto a surface. The consortium experimented with various combinations. The team chose the electrodeposition (ED) method. Superior in many ways, ED promises the ability to manufacture high-quality components at costs 50 % lower than alternatives. The process also yields rapid, reliable production of an efficient PV layer. Researchers also adapted the ED method to other materials, including absorbers, and considered the synthesis of buffer layers. A zinc compound (ZnO:CL) was chosen for the optical window layer. The material can be simply applied and, when combined with an organic solvent, has sufficient transparency and stability. Using the tested materials and methods, the consortium produced a lab-scale PV cell. The device had very poor conversion efficiency, yet the team determined the limiting factor to be the annealing temperature during manufacture. The group also tested and characterised promising nanophosphor-based materials. Based on the testing, the NANOCIS project was able to optimise the architecture design for future PV devices. The work promises a new generation of cheaper, highly efficient solar cells.
Keywords
Solar cells, photovoltaic, deposition methods, NANOCIS, CIGS, semiconductor
