Prime objective of the Sharc25 project is to develop super-high efficiency Cu(In,Ga)Se2 (CIGS) solar cells for next generation of cost-efficient solar module technology with the world leading expertise establishing the new benchmarks of global excellence. Both CIGS developers such as Empa (low temperature CIGS) and ZSW (high temperature CIGS) have developed new processing concepts which open new prospects for further breakthroughs leading to paradigm shift for increased performance of solar cells approaching to the practically achievable theoretical limits. In this way the costs for industrial solar module production < 0.35€/Wp and installed systems < 0.60€/Wp can be achieved, along with a reduced Capex < 0.75€/Wp for factories of > 100 MW production capacity, with further scopes for cost reductions through production ramp-up.
In this project the performance of single junction CIGS solar cells will be pushed from ~21% towards 25% by a consortium with multidisciplinary expertise. The key limiting factors in state-of-the-art CIGS solar cells are the non-radiative recombination and light absorption losses. Novel concepts are studied to overcome major recombination losses: combinations of increased carrier life time in CIGS with emitter point contacts, engineered grain boundaries for active carrier collection, shift of absorber energy bandgap, and bandgap grading for increased tolerance of potential fluctuations. Innovative approaches are applied for light management to increase the optical path length in the CIGS absorber and combine novel emitter, front contact, and anti-reflection concepts for higher photon injection into the absorber
Both CIGS developers (Empa and ZSW) could increase their solar cell efficiencies significantly, mainly by improved processes for CIGS absorber fabrication and advanced interface design. The best result of a small-area CIGS thin-film solar cells was 22.6%. In addition, parasitic absorption of the CdS buffer layer could be significantly reduced due to implementation of novel materials as subsequent high resistive layer. Further, a reflector was successfully introduced at the molybdenum back contact to increase the optical path length in the CIGS absorber. The Sharc25 project has provided deep insights into highly efficient CIGS thin-film solar cells using advanced characterization methods, analytical tools, device simulation, and density functional modeling.
