Perovksite-silicon tandem solar cells
Increasing solar cell efficiency is one of the most promising strategies for further reducing the cost of solar energy generation, but commercial silicon solar cells are fast approaching practical and theoretical efficiency limits. Combining industrial silicon PV technology with the latest perovskite materials in perovskite-silicon tandems will allow us to make more efficient use of the solar spectrum, and achieve efficiencies beyond that possible with either technology on its own.
Our group is working to develop both 2-terminal monolithic and 4-terminal mechanically-stacked tandem cells that take advantage of ANU’s world-class silicon solar and perovskite fabrication capabilities. We aim to develop stable and scalable perovskite-silicon tandem solar cell technology with efficiencies of 30% and beyond.
We are also applying our expertise to other tandem material systems including perovskite-CIGS.
Schematic illustration of an innovative interconnect-free monolithic, two-terminal Si/perovskite on commercialised Si technologies
Schematic illustration of a single-junction perovskite solar cell, consisted of multiple interfaces
Interfaces between the perovskite active layer, carrier transport layers, and electrodes play a crucial role in perovskite solar cells. Carrier recombination, charge extraction and transport, and hysteresis are all highly sensitive to interface properties and these can only be controlled through careful selection and optimization of materials and fabrication processes.
Our research covers both theoretical and experimental studies of interface properties, and the development of interface passivation, protective barrier layers and other strategies to improve cell performance and reliability.
One of the most fascinating, but also one of the most challenging, characteristics of perovskite solar cells is their dynamic response, which can span more than 12 orders of magnitude in timescale, from picoseconds to several days.
Over the last few years, our group has developed significant expertise in modelling the dynamic response of perovskite solar cells using numerical drift-diffusion models that can include one or more mobile ionic species. These models have provided valuable insights into the origins of hysteretic phenomena and have demonstrated that ion-recombination interactions are fundamental to explaining current-voltage hysteresis, transient photovoltage, photoluminescence and photocurrent responses, and even high-frequency electrical impedance. We are using these techniques to develop new experimental characterization methods to extract key cell parameters, and to better understand the performance of different cell materials and architectures.
PL intensity, spectral peak location, and extracted A maps of a perovskite solar cell versus exposure time in a room atmospheric environment. Column a-f correspond to different exposure times. The first row (1) is the PL intensity map. The second row (2) is the spectral peak location map. The third row (3) is the scaling factor SF map. The next row (4-7) are the extracted A maps at different wavelengths. In row 6, the white circles denote the localized features.
Comparisons of normalized luminescence spectra from a working perovskite solar cell (a) Schematic of the micro-PL mapping system. (b) PL spectra at various excitation powers. (c) EL spectra at various applied voltages, along with a PL spectrum. (d) Fitting to extrac the sample temperature.
We are developing and applying advanced spatial, spectral and temporal characterization tools and techniques to gain new insights into the material and device properties of perovskite solar cells and tandems. These include a number of advanced luminescence-based methods including photoluminescence and electroluminescence imaging, photoluminescence spectroscopy, and cathodoluminescence. Combining these methods with dynamic electrical analysis and numerical models allows us to probe the internal interaction of ions and charge carriers within the cells, and identify potential sources of instability and efficiency loss.
Improving Cell Stability
Achieving long-term reliability under realistic operating conditions is one of the most pressing challenges facing perovskite photovoltaic technology. We are developing new perovskite compositions, more stable carrier transport layers, and effective barrier materials to improve the stability of perovskite solar cells exposed to heat, humidity, UV light and other environmental stresses. We are also studying degradation processes that may not be apparent under standard IEC testing protocols, such as those induced by day/night cycling, and simultaneous application of light and heat.
Currently funded projects
1. Monolithic Si/Perovskite Tandem Solar Cell: Towards High-Efficiency at Low-Cost
Australian Renewable Energy Agency (ARENA) R&D Project (2020 - 2022)
Industry Partner: Risen Energy
Other Partners: University of Melbourne (UoM), Swiss Federal Institute of Technology Lausanne (EPFL), King Abdullah University of Science and Technology (KAUST)