Identifying and Eliminating Local Defects in Metal-Halide Perovskite Devices.
Lead Research Organisation:
University of Cambridge
Department Name: Physics
Abstract
Metal-halide perovskites have shown immense promise for optoelectronic applications such as solar cells and LEDs. However, defects
in the material and at interfaces with contact layers limit further improvements to device performance. In this work, we aim to elucidate the origin of defects and losses in metal-halide perovskites and at their interface with organic and inorganic charge extraction/injection layers. We will employ high resolution optical and X-ray based techniques on solution processed thin films and devices to determine the local distributions of defects, with the end goal of improving device performance with rational defect passivation.
in the material and at interfaces with contact layers limit further improvements to device performance. In this work, we aim to elucidate the origin of defects and losses in metal-halide perovskites and at their interface with organic and inorganic charge extraction/injection layers. We will employ high resolution optical and X-ray based techniques on solution processed thin films and devices to determine the local distributions of defects, with the end goal of improving device performance with rational defect passivation.
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509620/1 | 01/10/2016 | 30/09/2022 | |||
| 2127077 | Studentship | EP/N509620/1 | 01/10/2018 | 31/03/2022 | Kyle Frohna |
| EP/R513180/1 | 01/10/2018 | 30/09/2023 | |||
| 2127077 | Studentship | EP/R513180/1 | 01/10/2018 | 31/03/2022 | Kyle Frohna |
| Description | The goal of this project was to help to identify the complicated nanoscale landscape that electrons experience within an exciting new class of materials called halide perovskites. These materials have shown very good performance in applications including solar cells, light emitting diodes and detectors. One reason that they are very exciting is that they can be deposited in very cheap ways, such as by solution processing, printing or thermal evaporation. This means that in principle, high throughput manufacturing of these materials at relatively low capital cost is certainly possible. However, these low cost deposition methodologies mean that you have less control over the formation of the perovskite thin films, and as a result, the resulting perovskite are very heterogeneous by almost every metric. Rather than large single crystals that characterise materials like GaAs and silicon, these films are made up of many tiny grains hundreds of nanometres in size. Different regions of the film exhibit spatially varying chemical composition, crystal structures and crucially for the performance of these materials, trap state densities. Trap states, caused by defects in the material, trap electrons and holes and act as locations where they can lose their energy as heat rather than producing electrical energy. The concentration of trap states in perovskites is much higher than in traditional solar cell materials, however they still perform well (although they could still perform better). Understanding this nanoscale landscape is therefore crucial to improving the performance of these materials. Using state of the art microscopy techniques that we have developed, we have been able to significantly push forward our understanding of defects and the nanoscale landscape that charge carriers have to traverse in these materials. We have shown that alongside the spatially varying presence of nanoscale trap states, there is also a spatially varying chemical landscape. The chemical composition of the material varying creates energetic gradients that charge carriers fall down. We have shown that the chemical landscape funnels carriers away from detrimental trap states and endows the materials with enhanced defect tolerance. We may be able to tune and manipulate and tune this chemical in order to enhance this defect tolerance Furthermore, we have also been able to identify and characterise the different types of defects in these materials ,microscopically, and show which defects are detrimental and which defects are comparatively benign. This discovery will aid in subsequent material fabrication and allow us to pinpoint what are the defects that are still limting efficiency and help us rationally design strategies to overcome and eliminate them. |
| Exploitation Route | I believe that the microscopic insights that we have gained into the behaviour of these materials will enable us and others to rationally design the next generation of materials better. Additionally, the suite of tools that we have developed will be very useful for others in the community to characterise their own materials and better understand the changes they are making in the lab. Furthermore, some of our tools we have developed could certainly be implemented into production lines for the mass manufacture of perovskites or other technologies. |
| Sectors | Energy |
| Description | The work funded by this research has made considerable impact in the sense that it has been well covered in the media. The exciting nature of our findings, particularly in the recent publication on the chemical landscape of perovskites and their defect tolerance has been covered in several media outlets including the Irish Times, the Independent and the Daily Mail. The widespread coverage of these findings I believe will aid in their further development and implementation into policy further down the line. |
| Sector | Energy |
| Impact Types | Cultural |
| Title | Research data supporting "Nanoscale Chemical Heterogeneity Dominates the Optoelectronic Response of Alloyed Perovskite Solar Cells" |
| Description | This dataset is the full set of data to back up our paper published in 2021 in Nature Nanotechnology |
| Type Of Material | Database/Collection of data |
| Year Produced | 2021 |
| Provided To Others? | Yes |
| Impact | The resulting publication has proven impactful in the field thus far even though it was only published in November 2021 |
| URL | https://doi.org/10.17863/CAM.76854 |
| Description | Hard X-Ray Synchrotron Nanoprobe Collaboration with the Diamond Light Source |
| Organisation | Diamond Light Source |
| Country | United Kingdom |
| Sector | Private |
| PI Contribution | The I14 hard X-ray beamline is a relatively new beamline in the diamond light source facility. It provides the ability to probe the structure and chemisty of materials using X-rays with ~50 nanometre spatial resolution. We have brought our expertise on emerging materials for next generation photovoltaics and LEDs. We have been able to perform correlative microscopy between our own optical setups and the nanoprobe synchrotron setup, using this correlative approach that we have developed in partnership with the scientists at the I14 beamline, we have been able to demonstrate the capabilities of the beamline. |
| Collaborator Contribution | The I14 beamline has provided a state of the art X-ray nanoprobe setup for us to use. With back and forth communication between us and the beamline scientists, they have improved the capabilities, functionality and stability of the beamline each time we use it, enabling us to take better, more reliable and quicker measurements with each experimental session. |
| Impact | https://doi.org/10.1038/s41565-021-01019-7 https://www.science.org/doi/full/10.1126/science.abl4890 https://doi.org/10.1039/D1EE02055B https://doi.org/10.1002/adfm.202100293 |
| Start Year | 2018 |
| Description | Interviews for National and International News Outlets |
| Form Of Engagement Activity | A magazine, newsletter or online publication |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Public/other audiences |
| Results and Impact | We were interviewed for several international news outlets including the Irish Times, the Independent, the Daily Mail and UPI. The widespread coverage of the work has definitely increased attention on the area of new materials for renewable energy. |
| Year(s) Of Engagement Activity | 2021 |
| URL | https://www.irishtimes.com/news/science/breakthrough-could-be-key-to-harnessing-the-power-of-the-sun... |
| Description | Spoke to school in Dublin, Ireland |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Schools |
| Results and Impact | 30 pupils aged 10-12 attended the talk, asked questions about renewable energy and about science and being a scientist. School reported that the children were very interested in science in the subsequent weeks. |
| Year(s) Of Engagement Activity | 2022 |