Solar cells that replace expensive metal electrodes with carbon could halve the cost of perovskite solar panels, but they currently lag behind in efficiency—20 percent versus 26 percent for small devices. This project tackles that efficiency gap. Perovskite solar cells are cheap to print and already match the cost of solar electricity needed across Africa (18–49 dollars per megawatt-hour). But the most efficient versions rely on gold, silver, or copper back electrodes, which account for 98 percent of material cost, 65 percent of carbon footprint, and 45 percent of energy used in manufacturing. Carbon electrodes are far cheaper and more stable, yet the resulting cells consistently underperform. The researchers—a UK–South Africa collaboration—aim to reduce energy losses at the interfaces between layers and improve how light is trapped inside the perovskite material. If successful, the work would demonstrate printable carbon-electrode mini-modules (10 by 10 centimetres) with over 15 percent efficiency. That would make solar manufacturing cheaper, cleaner, and more scalable for off-grid and mini-grid systems in rural Africa, where over 80 percent of people without electricity live. The project also builds research capacity at the University of Pretoria, supporting South Africa’s shift toward affordable clean energy by 2030.
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Affordable energy for all Africans is the immediate and absolute priority in the Sustainable Africa Scenario (SAS) 2030. According to the International Energy Agency (IEA) Africa Energy Outlook 2022 report, solar energy-based mini-grids and stand-alone systems are the most viable solutions to electrify rural areas, where over 80% of the electricity-deprived people live [1]. Though Africa has 60% of the best solar resources globally, it has only 1% of installed solar photovoltaic (PV) capacity. Thus more investment and effective solar PV capacity building is required in the region to make electricity from clean energy sources as the backbone of Africa’s new energy systems. The existing silicon PV technology alone cannot meet this demand as it is an expensive mature technology, with global materials security issues, and enormous quantities of PV waste with poor recycling options [2]. Emerging PV technologies such as halide perovskite solar cells combine the unique properties of high power conversion efficiency (>25 %), low-cost printability, and provision to adopt a circular economy to ensure a sustainable clean energy transition for the region [3,4]. Halide perovskite PV offers the lowest cost of solar PV to date (<32 $ per MW h) and it matches with the levelised cost of electricity by solar PV (18-49 $ per MWh) required in Africa in the Sustainable Africa Scenario, 2020-2030. However, the mainstream highly efficient halide perovskite solar cells (PSCs) use thermally evaporated metals such as gold (Au), silver (Ag), copper (Cu) etc as the back electrode. These metals account for 98 % of the cost, 65 % of the carbon footprint and 45 % of the energetic cost of perovskite solar cells [5]. Replacing these metal electrodes with carbon electrodes enhances the stability, scalability and commercialisation aspect of PSCs along with further reduction in cost and carbon footprint. However, carbon back electrode-based PSCs (c-PSCs) have consistently lower power conversion efficiency (PCE) compared to metal electrode-based PSCs (m-PSCs) (20 % vs 26 % efficiency comparison for 0.1 cm2 area devices) limiting their commercialisation. The proposed project aims to bridge the gap in power conversion efficiency between the carbon-back vs metal electrode-based PSCs and demonstrate low-cost and highly efficient (>15 %) printable carbon electrode-based mini modules (10 x 10 cm2). This aim will be realised by combining the strengths of know-how in the fabrication and device physics of efficient halide perovskite solar cells of UK-based physicists with the defect analysis strengths of African physicists. To bridge this efficiency gap, the challenges to overcome are (i) reducing the interfacial losses and (ii) efficient photon management inside the perovskite active layer and the research objectives are identified accordingly. The proposed aims and objectives will formulate the foundations for achieving the vision for the proposed project: to provide accelerated growth in the scale-up of cheaper and cleaner energy sources in South Africa to achieve Sustainable Africa Scenario 2030 through capacity building in cost-effective and efficient PSCs in the partnering institution (University of Pretoria) in South Africa. References: IEA Africa Energy Outlook 2022 Charles et al Energy Environ. Sci., 2023, 16, 3711 Carneiro et al Energy Reports 2022, 8, 475 Faini et al MRS BULLETIN 2024, 49 Zouhair Sol. RRL 2024, 8, 2300929
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