RESEARCH FOCUSES

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.

Interface engineering

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. 

Numerical modelling

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.

Advanced Characterisation

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

Development of stable electrodes for perovskite solar cells

Australian Renewable Energy Agency (ARENA) R&D Project (2018 - 2021)

Project partner: Monash University

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Monolithic perovskite-silicon tandem cells: towards commercial reality

Australian Renewable Energy Agency (ARENA) R&D Project (2018 - 2021)

Project partner: Jinko Solar

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Engineering Stable, efficient perovskite solar cells

Australian Research Council (ARC) Discovery Project DP180100835 (2018 - 2021)

This project aims to resolve a critical issue facing perovskite solar cells: their instability under actual operating conditions where cells are subjected to diurnal (day-night) cycling. Over the diurnal cycle,changes in the electrochemical potential within the cell result in the movement of mobile ionic species. As these ions move through the perovskite material—and migrate into other layers that make up the solar cell—they can cause the cell to degrade by triggering decomposition of the perovskite material; corroding the contacts; and potentially causing delamination of the cell layers. 

While it is clear that mobile ionic species cause degradation, the link between ion migration and perovskite cell stability has yet to be fully determined. Critically, the most commonly-used testing regimes do not reflect real-world operating conditions and hence do not accurately evaluate stability. This project aims to systematically and rigorously evaluate strategies to prevent cell degradation due to ionic movement and to understand and prevent the instability of perovskite solar cells under operating conditions where cells are subjected to diurnal cycling.

Project partners: University of Maryland, Dr Andreas Fell (Fraunhofer ISE & AF Simulations)

Perovskite Photovoltaic Research at the Australian National University