Enhancing Perovskite Tandem Solar Cells—Comparative Analysis of Alternative Hole Transport Layers for Improved Efficiency and Stability

All perovskite tandem solar cells (APTSC) are garnering substantial attention within the solar cell community due to their remarkable improvement in power conversion efficiency (PCE). Since their initial demonstration, the PCE of APTSCs has surged from less than 5% to over 28% [1,2]. This rapid progress underscores the potential of APTSCs to revolutionize solar energy technology. At present, the highest-performing APTSCs predominantly employ PEDOT: PSS as a hole transport layer. Despite its widespread use, PEDOT: PSS has inherent drawbacks due to its acidic and hygroscopic nature, making it less than ideal for long-term solar cell applications. Its tendency to absorb moisture and degrade over time compromises the stability and efficiency of solar cells [3]. In response to these limitations, our research focused on identifying and testing alternative hole transport layers that could potentially enhance the performance and durability of APTSCs. We explored a variety of materials, including hole-selecting monolayers based on carbazole moieties, those without carbazole moieties, and inorganic hole transport layers such as nickel oxide (NiOx). By examining these alternatives, we aimed to determine their impact on the efficiency, light stability, and thermal stability of APTSCs. Our comparative analysis revealed that some of these alternative hole transport layers exhibit promising improvements in the stability and efficiency of APTSCs. For instance, solar cells utilizing monolayers without carbazole moieties demonstrated significant enhancements in both PCE and light stability. These findings suggest that the selection of appropriate hole transport materials is critical for optimizing the performance of perovskite tandem solar cells. Additionally, we conducted comparative studies on tin-lead (Sn-Pb) solar cells incorporating various hole-selective monolayers. It was observed that conventional PEDOT and 2PACz exhibited substantial declines in performance under prolonged light exposure. Conversely, the monolayers without carbazole moieties, referred to as A and B in our study, significantly improved the PCE and light stability of the solar cells. These improvements highlight the potential of these alternative materials to facilitate more robust and efficient APTSC fabrication processes. This research provides valuable insights into the development of more efficient and stable perovskite tandem solar cells, paving the way for their broader adoption in the renewable energy sector. By advancing the understanding of alternative hole transport layers, we contribute to the ongoing efforts to enhance the viability and longevity of APTSCs. The positive outcomes of our study could accelerate the integration of APTSCs into commercial solar energy solutions, ultimately supporting the global transition to sustainable energy sources.<br/><b>References:</b><br/>1. R. Lin and H. Tan et al, Nature, 2023, 620, 994-1000.<br/>2. J. Marko and S. Albrecht et al, Adv. Energy Mater., 2020, 10, 1904102<br/>3. G. Kapil and S. Hayase et al., ACS Energy Letters, 2022, 7, 966-974.