Bridging the Efficiency Gap of Metal vs Carbon back Electrode Perovskite Solar Cells to Support the Clean Energy Growth Transition in South Africa

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...