Description
The proposed project, N-IBCell, aims to fabricate high efficiency intermediate band solar cells (IBSCs). These are solar cells designed to absorb below bandgap energy photons by means of an electronic energy band that is located within the host semiconductor bandgap. They thereby produce enhanced photocurrent while ideally maintaining the photovoltage given by the host photovoltaic material bandgap. IBSCs have a theoretical efficiency limit of 63.2%, 50% higher than the limit for standard solar cells. Another advantage of IBSCs is their simplicity, and hence their reduced production costs, as they require a single p-n junction only. The Romanian and Norwegian partners will merge in this project their respective and complementary competences through opened discussions and exchanges on results and planning, in order to promote an efficient synergy to meet the objectives of this collaborative work. This project opens up a new collaboration between Romanian and Norwegian laboratories and this is regarded as very exciting and promising.
Summary of project results
High efficiency solar energy conversion is crucial. Solar cells, also called photovoltaic (PV) cells, are devices that convert sunlight energy directly into electricity by photovoltaic effect. The major obstacle to widespread use of PV systems is still the high cost of PV electricity, which is still greater than the cost of energy produced from fossil fuels, the production and installation cost of these systems having nearly fixed costs. The proposed project addressed both problems by focusing on intermediate band solar cells (IBSCs) which have a simple design and, hence, simple costs, but, at the same time, showing potential (63.2%) for high conversion efficiency of solar energy. The common project aimed by fundamental and experimental studies to improve the performance of IBSCs, based on compound semiconductors containing nitrides, whose energy levels are generated by either a 3D architecture of quantum dots or using dilute nitride compound semiconductors, whose native energy levels makes them appropriate for realization of IBSCs. Through the prism of the results there was achieved the validation of the initially proposed solutions of the project. Comparing the obtained results to the initially proposed strategies of the project, it has been showed that by an appropriate mediation of the highly compressive strain of the 3D In(N)As quantum dots assemble, part of an intermediate band solar cell, an enhancement of the cell photocurrent and photovoltage can be achieved. A more significant enhancement (reaching even one order of magnitude for certain samples) of photocurrent accompanied by an increase of photovoltage could be observed by using the quaternary compound GaInNAs for replacing the older ternary material GaNAs in intermediate band solar cells. Validation of the initially proposed solutions through the prism of the results has been acted as a strong momentum for both partners to further promote these results also in other materials systems or solar cells heterostructures concepts with potential for high conversion efficiencies.
Summary of bilateral results
The Romanian and Norwegian partners merged in this project their complementary competences through opened discussions and exchanges on results and knowledge, promoting an efficient synergy to meet the objectives of this collaborative work. This project opened up a new collaboration between Romanian and Norwegian laboratories, with promising future perspectives. As a matter of fact, the extensive experience of project investigator in MBE growth and characterization of group III-N alloys, particularly dilute nitride alloys, and the deep knowledge of the Norwegian group leader in designing intermediate band solar cells constituted key collaborative taking into account the intention of the Norwegian partner to grow dilute nitride alloys and the intention of the Romanian partner to develop intermediate solar cells. The project acted as a great opportunity to know better each other in order to envisage further common works, especially on European-funded projects.