PP3.2f Light Trapping in Organic Photovoltaics
A range of advanced techniques and tools for characterisation of photovoltaic materials is underway, in four main strands.
- Excitonic Binding Energy Measurement
The effect of excitonic binding energy on absorption spectra is subtle, but important for material and cell optimisation. Theoretical values for silicon, copper-zinc-tin-sulphur (CZTS) and perovskites need to be experimentally verified. Standard reflection-transmission (R/T) spectroscopy techniques are not sufficiently sensitive to measure this. UNSW is building a customised system that is three orders of magnitude more sensitive to these spectral changes compared to standard systems. The technique measures differential changes of the R/T spectrum by forming a lock-in signal between two wavelengths instead of measuring absolute intensities.
- Time-Resolved Photoluminescence Model - from Silicon Wafers and Bricks
Time-resolved photoluminescence measurement data contain information about surface- and bulk lifetimes. Current mathematical models are not sufficient to extract all lifetime data from measurements. In order to use measurement data more efficiently, a sophisticated mathematical model and realistic algorithms are required.
- Advanced System for Time-Resolved Photoluminescence Measurements
Time and spectral resolved photoluminescence spectroscopy are two of the most powerful characterisation techniques for photovoltaic materials. For a better understanding of complex material characteristics it is necessary to combine both techniques into one system. This would allow seamless parameter sweeps to study better electronic- and optical-band structures, various carrier lifetimes, defect characteristics and transport phenomena. Relatively new materials such as perovskite and copper-zinc-tinsulphur (CZTS) would benefit most from such a system
- Injection Dependent Short Lifetime Measurement
Injection dependent carrier lifetimes are one of the most important material characteristics in PV research. Materials, such as GaAs, CZTS, perovskite and quantum dots, have very short lifetimes in the low ns range. Existing measurement instruments can measure their lifetimes, but not injection dependence. Due to the stronger focus on such materials, our school has decided to build a system with such capabilities.