Benzothiadiazole perovskite solar cell
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Benzothiadiazole Perovskite Solar Cells: Advances and Insights
Introduction to Benzothiadiazole in Perovskite Solar Cells
Benzothiadiazole (BT) has emerged as a significant component in the development of hole transport materials (HTMs) for perovskite solar cells (PSCs). Its unique electron-accepting properties and ability to be modified with various functional groups make it a versatile building block for enhancing the efficiency and stability of PSCs.
Fluorine-Substituted Benzothiadiazole for High Efficiency
Recent studies have shown that incorporating fluorine-substituted benzothiadiazole into HTMs can significantly improve the performance of PSCs. For instance, monofluorinated BT-based HTMs have achieved a power conversion efficiency (PCE) of 18.54% with a fill factor (FF) exceeding 80%. This high efficiency is attributed to the improved hole transport properties and better energy level alignment with the perovskite layer.
Benzothiadiazole Aryl-Amine Based HTMs
Benzothiadiazole aryl-amine based materials have also been explored as efficient hole carriers in PSCs. These materials, synthesized using a push-and-pull approach, have demonstrated a PCE of 18.05% in triple-cation mixed-halide PSCs. The combination of BT as an electron acceptor and diphenyl- and triphenyl-amines as electron donors helps in modulating the highest occupied molecular orbital (HOMO) energy level, enhancing hole mobility, and ensuring thermal stability.
Molecular Engineering for Enhanced Performance
Molecular engineering has been employed to incorporate BT as a core unit in new HTMs, such as JY5, which has shown excellent thermal stability and hole transport ability. PSCs utilizing JY5 have achieved a champion efficiency of 16.87%, outperforming biphenyl-centered analogues. This highlights the potential of BT-based HTMs as cost-effective alternatives to traditional materials like Spiro-OMeTAD.
Dopant-Free Benzothiadiazole-Based HTMs
The development of dopant-free BT-based HTMs has shown promising results in terms of efficiency and stability. For example, a novel HTM derived from BT, CF-BTz-ThR, has achieved a PCE of approximately 15.4% with a short circuit current density (Jsc) of 22.42 mA cm-2 and an open circuit voltage (Voc) of 1.02 V. Additionally, D-A-D typed HTMs with BT acceptor units and fluorine atoms have demonstrated a PCE of 12.1% and significantly improved long-term stability.
Planarity and Hole Mobility
Enhancing the molecular planarity of BT-based HTMs by introducing thiophene bridges has been shown to lower the band gap and increase hole mobility. This approach has led to a significant improvement in the PCE and stability of PSCs, with devices maintaining 83% of their initial efficiency after 15 days.
Polymeric HTMs for Stability
Polymeric HTMs based on BT and benzo[1,2-b:4,5-b']dithiophene have also been developed, achieving a PCE of 17.3% and maintaining efficiency for over 1400 hours at 75% humidity. These materials avoid the use of deliquescent or hygroscopic dopants, further enhancing device stability.
Conclusion
Benzothiadiazole-based HTMs have shown great potential in improving the efficiency and stability of perovskite solar cells. Through various molecular engineering strategies, including fluorine substitution, aryl-amine integration, and the development of dopant-free and polymeric HTMs, researchers have achieved significant advancements in PSC performance. These findings underscore the importance of BT in the ongoing development of high-efficiency, stable, and cost-effective perovskite solar cells.
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