LOVETandemSolar · Local Optoelectronic Visualisation for Enhancing Tandem Perovskite/Silicon Solar Cells

Local Optoelectronic Visualisation for Enhancing Tandem Perovskite/Silicon Solar Cells

Standard Silicon (Si) solar cells achieve stable and high efficiencies, however, this photovoltaic (PV) technology faces challenges ahead, as the demand for renewable energy solutions continues to rise amidst the global energy transition. The world requires a large roll out of PV to meet development and energy goals, and a boost in power-conversion efficiency (η) of these devices enables more power output per area. Importantly, this means less materials will be needed to meet the equivalent energy demand, which leads to an ease of pressure on land use, industry manufacturing, and supply chains. To achieve higher efficiency PV technologies that are still based on low-cost Si, cutting-edge researchers are adding an additional, microscopic layer of a semiconductor material, perovskite, on top of the Si device. The perovskite layer conformally coats the Si and absorbs portions of the sun’s light (specifically, bluer light or higher energy light) that enables an increase in η. The perovskite absorber on top of the Si is what researchers call a monolithic perovskite/Si tandem device, or a multi-junction solar cell. However, the coating process of the microscopic perovskite layer is difficult, particularly because the surface of Si-based PV devices is often not flat. Rougher surfaces are used in PV technology because this supports the scattering of light and enables reabsorption, yet it makes it difficult to coat on. State-of-the-art PV technology shows that coating perovskite on rough Si surfaces is possible and can be done in a conformal manner – but the optimal texturing for balancing both device performance and ease-of-fabrication remained undetermined. As such, the goal of this project was to interrogate the textured nature of perovskite/Si tandem solar cells and its influence on the device performance at a microscopic level. The primary research questions were: “How do the distinct micro- and nanoscale constructs effect device performance locally?”, “What happens to the optical properties of both the perovskite and Si materials when they are fabricated as a stack, rather than independently?”, and “Will fabricators need to re-tune the texturing pattern on this device stack to achieve enhanced solar harvesting efficiency?” To answer these questions, and subsequently build upon their learnings, the follow objectives were designed for this project: • Objective 1: Develop and implement advanced metrology and microscopy techniques for textured perovskite/Si tandem solar cells • Objective 2: Macroscopic characterisation and modelling of the optical properties of multi-junction solar cells • Objective 3: Use data analytics to correlate complex and/or difficult-to-find scientific findings • Objective 4: Boost the power-conversion efficiency of textured perovskite/Si tandems In conclusion, we have successfully implemented the first three objectives during the project, all of which were presented in a paper published in ACS Energy Letters (DOI: 10.1021acsenergylett.1c00568). The contributions of this research project then informed our collaborators of the potential texturing pattern that could enable a boost in efficiency (Objective 4). I am delighted to remark that earlier this year (2022) our collaborators indeed were able to obtain the new record η for perovskite/Si tandem textured (and non-textured) devices, and fabricate the first of such kind that broke through the 30% efficiency barrier: https://www.csem.ch/page.aspx?pid=172296.

Data: CORDIS, © European Union