Achieving an Efficient and Stable Morphology in Organic Solar Cells Via Fine-Tuning the Side Chains of Small-Molecule Acceptors

Abstract

Both the efficiency and stability of low-cost organic solar cells are central components for meeting the requirements of commercialization for organic photovoltaics (OPV). Furthermore, the relationship between the chemical structure of an active material and morphology and its effects on efficiency and stability is still largely undetermined. Additionally, both the kinetic and thermodynamic morphology states of an active layer can have a huge impact on efficiency and stability, even when the chemical structures of materials applied in the active layer are especially the same or similar. Here, using two series of acceptor–donor–acceptor (A–D–A)-type small-molecule acceptors (SMAs) with similar backbone structures, we demonstrate the relevance of fine-tuned chemical structures with their solution and solid-state properties, further leading to significantly different behavior in terms of both device efficiency and stability. This is also partially due to the different morphology states caused by such fine chemical structure tuning. Our results indicate that a delicate balance of molecular aggregation and ordered stacking morphology is required to achieve and lead to high efficiency and stability. Thus, among the two series of molecules, UF-EH-2F, with both optimal length and steric hindrance of side chains, achieves the preponderant morphology in its corresponding device, where its morphologies “efficient state” and “stable state” are almost overlapped, and thus lead to both the highest efficiency (power conversion efficiency, PCE = 13.56%) and the best stability. Our results indicate that it is highly possible to achieve the morphology state required for both high efficiency and stability simultaneously by fine-tuning the chemical structure of active materials for organic solar cells.

Enhancing Long‐Term Thermal Stability of Non‐Fullerene Organic Solar Cells Using Self‐Assembly Amphiphilic Dendritic Block Copolymer Interlayers

“…According to the previous results, the morphological change of BHJ layer might be the main reason because the thermal‐induced micro‐phase separation will deteriorate the charge transport and dissociation efficiency. [ 24 ] Notably, we also measured the ambient and thermal stability of the devices based on the PTB7‐Th:ITIC blend system. As presented in Figure S9, Supporting Information, the DBC@AuNPs device still showed the highest ambient and thermal stability among the studied devices.…”

Progress in Materials, Solution Processes, and Long‐Term Stability for Large‐Area Organic Photovoltaics

“…Spin coating is the most representative method employed to form constituent layers in an OPV device, including the photoactive layers, [67][68][69] hole-and electron-transport layers, and the electrodes. [70,71] In detail, the spin coating process involves four steps: i) solution casting onto the substrate; ii) solution thinning by radially outward flow due to centrifugal force; iii) ejection of the solution from the perimeter of the substrate; and iv) further thinning and drying of the film by solvent evaporation.…”

Achieving Efficient Ternary Organic Solar Cells Using Structurally Similar Non‐Fullerene Acceptors with Varying Flanking Side Chains

“…Organic solar cells (OSCs) have attracted considerable attention and widespread research interest due to the unique advantages such as light weight, flexibility, semi‐transparency, and low‐cost fabrication by solution processing methods. [ 1–15 ] Recently, non‐fullerene OSCs have been developing rapidly with power conversion efficiencies (PCEs) of over 17% achieved by single‐junction devices. [ 16–22 ] These advances can be largely attributed to the emergence of high‐performance non‐fullerene acceptors (NFAs).…”