Charge separation at perovskite/singlet fission material interfaces
As solar cells continue to improve, their efficiencies will approach the Shockley- Queisser limit of 33%. To overcome this limit, multiple photovoltaic materials must be combined. The conventional approach of overcoming this limit is to create tandem solar cells, but these are expensive to produce, limiting widespread applications. Down-conversion technologies, which utilise singlet fission, are nascent but hold much promise as their cell architecture is simpler than that of tandem cells, reducing production costs.
The first aim of this project is to demonstrate the potential of down-conversion solar cells by using bilayers of metal halide perovskites and tetracene (a well-known down-converter). This has the potential to increase the efficiency of solar cells to 44%. By tuning the composition of the perovskite, we can tune the perovskite conduction band energy level while maintaining a constant band-gap energy, which should allow for aligning its energy levels with those in tetracene. To date, no singlet fission material has been successfully integrated with a perovskite cell.
A second aim of this project is to address charge transfer at inorganic/organic interfaces. It has been observed that exciton dissociation is enhanced due to the mobility mismatch between organics and inorganics. It is hoped that this will be observed in perovskite/tetracene interfaces. A theoretical approach will also be taken to this problem, modelling charge transfer at the interface, with the aim of quantifying the probability of charge transfer from fissile materials to perovskites. Such a formula would assist with fine-tuning the design of future singlet fission/perovskite solar cells.
Dr. Sam Stranks