About this Research Topic
Renewable energy represents the only feasible solution to remediate global warming and its devastating effects on human life and ecosystems. Solar energy is one of the main opportunities to reach the zero-carbon horizon, providing 296 GW of the global renewable power generation. In this context, photovoltaic technology (PVs) represents the major contributor, mostly managed (90%) by crystalline silicon semiconductors solar cells. However, silicon devices are not enough to achieve the strict requirements of efficient deployment of PVs on a global scale, low manufacturing costs and enhanced power conversion efficiency (PCE). Fortunately, semiconductors devices based on perovskite-type structures have been revolutionizing the filed. The stunning optoelectronic properties of these materials allow the tuning of its bandgap over an extensive range. This allows perovskites to be layered in all-perovskite multi-junction cells (narrow bandgap), and used also as top device assembled in hybrid tandem architectures (wide-bandgap) with silicon bottom cells, pushing the crystalline silicon market beyond its theoretical limits.
The tandem assembling could be done in both monolithic two-terminal (2T) and mechanically stacked four-terminal (4T) configurations. The 4T are easier to prototype, but suffer from parasitic absorption and reflections. This fact represents just an example of the multiple requirements and challenges that governs the fabrication of reliable tandem solar cells. That is, fabrication process should be scalable enough to maintain the costs, matching as well silicon's 25 years lifetime.
The scalability of the process should take into account: transparent conducting electrodes, thermally and chemically robust perovskite materials, a recombination layer to allow current to flow, compatible processing of the two cells and a maximized light harvesting. Regarding the stability enhancement, there are two fundamentals aspects to consider: a scientific one, concerning the physical-chemical robustness of the perovskite cell itself and its interfacial interactions with the bottom silicon device, and a technological one, which addresses mainly the encapsulation processing and the materials used for that. Recent studies have demonstrated the possibility to directly grow perovskite materials onto the silicon cell. This possibility brings us one step closer to the commercialization of tandem cells. In this regards, two examples of the developments recently achieved are: a solution processing onto textured crystalline silicon using passivation additives; a dry two-step conversion process that incorporates lead oxide sputtering and direct contact with methyl ammonium iodide.
The purpose of this Research Topic is to call for further research exploring in depth reliable scalable technologies for efficient perovskite/Si tandem solar cells. The latest developments in encapsulation process and material engineering to ensure the stability of the devices are also called.
Subjects covered in this Research Topic include, but are not limited to:
• 2T versus 4T
• All inorganic perovskite materials for high stability.
• Silicon surface passivation methods to facilitate perovskite growing.
• Alternatives for direct contact maintaining efficiencies.
• Tandems for solar fuel production.
• Optoelectronic characterization of perovskite/silicon solar cells.
• All-tandem perovskite onto flexible substrates.
• Novel encapsulation methods for PSCs/Si tandem solar cells.
Keywords: Perovskite, Silicon, Tandem, Photovoltaic, Energy
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