EPSRC-FNR Collaborative Proposal: Radiative Efficiency in Advanced Sulfide Chalcopyrites for Solar Cells (REACh)
Lead Research Organisation:
University of Cambridge
Department Name: Materials Science & Metallurgy
Abstract
The renewable and carbon free energy system of the future will rely heavily on electricity generated by solar cells. Solar modules have decreased in price so much in the last few years, that now the cost related to the rest of the system has becomes the main expense. These cost are related to the area of the solar cell. Therefore it remains essential to increase the efficiency of solar cells, because then we need less area to produce the same amount of electricity.
Conventional solar cells have been refined over several decades and their efficiencies are now approaching theoretical limits. A new way forward is provided by tandem solar cells, where we stack two different solar cells on top of each other, so that each can make better use of the solar spectrum and the efficiency becomes higher. We are working on a new material, sulfide chalcopyrite, which can be used in a thin film (using only small amounts of raw materials), is stable and has already shown promising efficiencies. We want to use this material as the top cell, combining it with well-known solar cell materials like silicon to produce a tandem cell. These thin films are not single crystals but consist of tiny crystals - on the micrometre scale - known as "grains", which are butt up against one another at "grain boundaries". These grain boundaries can be problematic because they differ from the perfect crystal, and are hence places where we can lose the electrons generated by the incoming sunlight at a rapid rate. Also, grain boundaries can block the current moving through the solar cell. Usually, there are many different grain boundaries in a thin film, some are detrimental for the solar cell and some are benign.
In this project we want to understand the role of grain boundaries in sulfide chalcopyrite solar cells. We will study luminescence, which is the light that is emitted by a solar cell material when it is excited by a laser or an electron beam, thereby generating electrons. We use this light to check the quality of the thin films. A good solar cell material will also emit a lot of luminescence, because the electrons that lead to light emission are also those that would carry the current in the solar cell - and if they are able to emit light they are not lost at defects like grain boundaries. For the best films we will use an electron microscope, which allows us to study the luminescence with a very high spatial resolution. Thus, in the electron microscope, we can examine each individual grain boundary and see how much it affects the luminescence. We can then check with the electron microscope what is special about those grain boundaries that do not lead to loss of electrons. This information will help us adapt the growth process of our thin films to make them into better solar cells, by avoiding growth of the more damaging types of grain boundary.
Conventional solar cells have been refined over several decades and their efficiencies are now approaching theoretical limits. A new way forward is provided by tandem solar cells, where we stack two different solar cells on top of each other, so that each can make better use of the solar spectrum and the efficiency becomes higher. We are working on a new material, sulfide chalcopyrite, which can be used in a thin film (using only small amounts of raw materials), is stable and has already shown promising efficiencies. We want to use this material as the top cell, combining it with well-known solar cell materials like silicon to produce a tandem cell. These thin films are not single crystals but consist of tiny crystals - on the micrometre scale - known as "grains", which are butt up against one another at "grain boundaries". These grain boundaries can be problematic because they differ from the perfect crystal, and are hence places where we can lose the electrons generated by the incoming sunlight at a rapid rate. Also, grain boundaries can block the current moving through the solar cell. Usually, there are many different grain boundaries in a thin film, some are detrimental for the solar cell and some are benign.
In this project we want to understand the role of grain boundaries in sulfide chalcopyrite solar cells. We will study luminescence, which is the light that is emitted by a solar cell material when it is excited by a laser or an electron beam, thereby generating electrons. We use this light to check the quality of the thin films. A good solar cell material will also emit a lot of luminescence, because the electrons that lead to light emission are also those that would carry the current in the solar cell - and if they are able to emit light they are not lost at defects like grain boundaries. For the best films we will use an electron microscope, which allows us to study the luminescence with a very high spatial resolution. Thus, in the electron microscope, we can examine each individual grain boundary and see how much it affects the luminescence. We can then check with the electron microscope what is special about those grain boundaries that do not lead to loss of electrons. This information will help us adapt the growth process of our thin films to make them into better solar cells, by avoiding growth of the more damaging types of grain boundary.
Publications


Peedle S
(2023)
Role of nanoscale compositional inhomogeneities in limiting the open circuit voltage in Cu(In,Ga)S2 solar cells
in APL Energy

Prot A
(2023)
Composition variations in Cu(In,Ga)(S,Se)2 solar cells: Not a gradient, but an interlaced network of two phases
in APL Materials


Prot A
(2024)
Improved Sequentially Processed Cu(In,Ga)(S,Se) 2 by Ag Alloying
in Solar RRL
Description | We have developed new methods to understand how the small scale structure of solar cells can be linked to the solar cell's performance. We have applied these methods to new solar cell materials. |
Exploitation Route | Our findings are being used in the development of new solar cell materials. |
Sectors | Electronics Energy |
Description | We have an ongoing collaboration with Avancis which is contributing to industrial optimisation of solar cell materials. |
First Year Of Impact | 2023 |
Sector | Electronics,Energy |
Impact Types | Societal Economic |
Description | EPSRC-Innovate UK Semiconductor Technology Roundtable |
Geographic Reach | National |
Policy Influence Type | Participation in a guidance/advisory committee |
Description | EPSRC/Innovate UK Semiconductor Roundtable |
Geographic Reach | National |
Policy Influence Type | Contribution to a national consultation/review |
Description | FCDO UK Semiconductor Sector Visit to Washington DC |
Geographic Reach | Multiple continents/international |
Policy Influence Type | Contribution to a national consultation/review |
Description | FCDO/DSIT Semiconductor Delegation to Washington |
Geographic Reach | Multiple continents/international |
Policy Influence Type | Contribution to a national consultation/review |
Description | Institute of Physics / Royal Academy of Engineering Roundtable: UK Semiconductor Challenges and Solutions |
Geographic Reach | National |
Policy Influence Type | Contribution to a national consultation/review |
URL | https://raeng.org.uk/media/2hmbvzke/0402_semi-conductor-report_v2.pdf |
Description | RAEng - Quantum Infrastructure Review - Working Group |
Geographic Reach | National |
Policy Influence Type | Contribution to a national consultation/review |
Description | eFutures DSIT Semiconductors Project Advisory Group |
Geographic Reach | National |
Policy Influence Type | Contribution to a national consultation/review |
Title | Research data supporting "Role of Nanoscale Compositional Inhomogeneities in Limiting The Open Circuit Voltage in Cu(In,Ga)S2 Solar Cells" |
Description | Datasets associated with the Publication "Role of Nanoscale Compositional Inhomogeneities in Limiting The Open Circuit Voltage in Cu(In,Ga)S2 Solar Cells" . All data was acquired in an Attolight Allalin 4027 Chronos dedicated CL-SEM with a 150 l/mm and 500 nm blazed grating. All measurements were taken at room temperature with an electron beam acceleration voltage of 6.0 kV and a current of 3.0 nA with 90% of the beam energy being deposited within a depth of ~ 150 nm according to Monte Carlo CASINO simulations. Initial CL images were observed to suffer from significant drift due to charging, so the samples were carbon-coated to improve the conduction of the beam electrons away from the surface. All data treatment was performed using the Python hyperspy library. |
Type Of Material | Database/Collection of data |
Year Produced | 2023 |
Provided To Others? | Yes |
URL | https://www.repository.cam.ac.uk/handle/1810/354473 |
Description | Royal Academy of Engineering Critical Conversation |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | In March 2023, semiconductors were listed as the one of 'five technologies that are most critical to the UK' in the government's UK Science and Technology Framework. This online discussion event, hosted by the CEO of the Royal Acdemy of Engineering, explored the latest challenges, and opportunities, with engineers at the forefront of semiconductor research and industry, including Rachel Oliver. A live audience of over 100 watched and it has since been viewed about 300 times on Youtube. As a result of t6his engagement, Rachel was asked to join the eFutures DSIT Semiconductors Project Advisory Group. |
Year(s) Of Engagement Activity | 2023 |
URL | https://raeng.org.uk/events/2023/september/semiconductors-a-critical-technology-for-a-critical-time |
Description | The Context - interview |
Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | I was interviewed on "The Context" on the BBC News Channel about the UK Semiconductor Strategy shortly after its publication. |
Year(s) Of Engagement Activity | 2023 |