| Author: | Lang, Yongwen |
| Title: | Photoactive layer manipulation toward highly efficient and stable organic solar cells |
| Advisors: | Li, Gang (EEE) |
| Degree: | Ph.D. |
| Year: | 2025 |
| Department: | Department of Electrical and Electronic Engineering |
| Pages: | 189 pages : color illustrations |
| Language: | English |
| Abstract: | Organic solar cells (OSCs) possess promising merits of transparency, flexibility, low pollution, and roll-to-roll processability, making them a dynamic research area. Currently, the power conversion efficiencies (PCEs) of OSCs have surpassed 20%. However, there are many issues to be addressed for practically used long-term stable high-performance OSCs, for example, the crystallization kinetics and morphological controlling in large-area production, the lagged PCEs for eco-friendly solvent-processed OSCs, and the inferior material and device stability. Therefore, the thesis proposed corresponding strategies to address these issues. The first work proposed a solubility-tuning strategy by the multi-component approach to address the hard-controllable film aggregation kinetics and morphology issue in upscaling manufacturing (doctor-blade coating). The solubility tuning by incorporating a twisted third component (BTP-4Cl) can induce rapid crystallization behavior and promote fine phase separation in blade-coated blends. As a result, a PCE of 19.67% is obtained in OSCs (0. 04 cm²), which is one of the state-of-the-art efficiencies among the reported blade-coated OSCs. This work offered novel insights into the effectiveness of solubility-tuning approaches for achieving highly efficient and stable OSCs under open-air coating conditions and provided a deeper understanding and appraisal of film formation kinetics influenced by coating methods. The second work synthesized two highly crystalline 2D acceptors ATIC-C11 and ATIC-BO to construct highly efficient and stable halogen-free solvent-processed OSCs. The difference in side chains induces ATIC-C11's crystal structure to be an elliptical framework, and ATIC-BO a rectangular framework. ATIC-BO's strong self-aggregation and immiscibility induce large aggregates and severely impede charge transfer (CT) and dissociation. Conversely, ATIC-C11's suitable crystallinity and compatibility positively regulate the crystalline kinetics during film formation, thus forming much-ordered molecular packing and favorable phase separation size in blend films. As a result, ATIC-C11-based ternary devices achieve a high efficiency of 19.28% with potential in scalability and stability, which is the top-ranking efficiency among nonhalogenated solvent-processed OSCs. This work not only displays highly efficient and stable halogen-free solvent-processed OSCs but also offers a new thought for material design and selection rule on the third component in highly efficient ternary OSCs. The third work synthesized two central core-extended acceptors, PhIC-BO and AnIC-BO, regarding synergistic enhancement in efficiency and stability. The improvement in efficiency was ascribed to the suppressed recombination loss, optimized molecular packing, facilitated exciton generation, and higher charge and energy transfer efficiency. The increment in stability was attributed to the suppressed material oxidation degradation, improved domain purity, and impeded molecular interdiffusion. Additionally, the two acceptors’ difference in electron-deficient central cores affords their different crystal structures, carrier dynamics, and morphological microstructures. As a result, a high PCE of 19.44% was achieved in the PhIC-BO-based OSCs, along with outstanding operational stability. Therefore, this work not only established a high-performance and long-term stable OSC but also provided deep insight into understanding the correlation between structures and properties. In summary, these works mainly focus on addressing the problems in achieving highly efficient and stable OSCs towards commercialization and industrialization. We expected that these works would provide valuable guidance for further research. |
| Rights: | All rights reserved |
| Access: | open access |
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