The Hot Carrier Solar Cell

closed

The aim of this project was to develop a prototype Hot Carrier (HC) solar cell and establish routes toward the development of practical devices. The HC solar cell is a promising advanced photovoltaics or so called “third generation” concept which aims to tackle the major efficiency loss in conventional solar cells.This project builds on earlier UNSW research that identified the most effective materials and design for a Hot Carrier (HC) solar cell. HC solar cells are able to convert more solar energy to electricity than existing solar cells by slowing down the cooling of the ‘carriers’ which hold the energy contained in sunlight, and more effectively harvest that energy. This project involves the further development of the technology and construction of a working model (or prototype) of the HC solar cell. The project researchers are also examining the use of abundant materials and commercially available production methods, both of which would reduce the overall cost of generating solar electricity from this technology.Key resultsThis project has successfully achieved the proposed outcomes including development of a prototype HC Solar Cell and the development of a practical device. There is great scope to improve the performance of the HC solar cell devices. In the short term future, device performance may be significantly improved by: (a) improvement in the quality of thin film absorber, (b) determination of the qualitative and quantitative effects of quantum well and barrier thickness and differences in acoustic impedance, and (c) device integration.Further work focussing on improving quality and reliability is required to develop the model for commercial viability. The development of the HC solar cell will tackle the major loss in conventional solar cells due to the loss of the excess energy of the “hot” carriers (carriers with energy above the fundamental energy level of the solar cell – the ‘band gap energy’) generated by the high energy photons in the solar spectrum. In typical solar cell materials these “hot” carriers lose their excess energy as heat or lattice vibrations in a few trillionths of a second. HC solar cells aims to collect these carriers before they are lost.Project innovationThis project examined the feasibility of third generation solar cell technology, the Hot Carrier (HC) solar cell. The HC solar cell is very efficient in converting solar energy to electricity and inexpensive to manufacture, thereby reducing the overall cost of generating solar electricity.The HC solar cell is able to convert more solar energy to electricity than existing solar cells by slowing down the cooling of the ‘hot carriers’ which hold the energy transferred by sunlight.A range of materials (called HC absorbers) were examined to identify those which best prevented or minimised the cooling of the hot carriers which allowed more time to harvest the energy they contain. This allowed the solar cell to deliver higher voltages.The project also identifed the most effective structures to collect the hot carriers without losing much of the energy they contain through energy selective contacts (ESCs).Computer modelling was used to identify the most effective materials and structures for HC absorbers and ESCs, and the best way to combine them in a complete HC solar cell prototype.BenefitThe identification of effective materials and design for a successful Hot Carrier solar cell will help to significantly reduce the cost of manufacturing and operating solar energy technologies.

High