Fabrication of high-efficiency organic solar cells (OSCs) using nonhalogen green solvents is highly desired for commercialization. However, the morphology control of a nonhalogen solvent-processed active layer remains challenging because of poor solubility of the commonly used photovoltaic materials in nonhalogen solvents. Herein, we propose a two-step heating strategy to optimize the morphology of a photovoltaic active layer based on a low-cost polymer donor X1 and a small-molecule acceptor (SMA) BTP-eC9 processed from a mixed nonhalogen solvent. First, heating the blend solution can robustly enhance the solubility of the SMA and thus processability of the blend, producing a uniform active layer. Second, further elevating the substrate temperature can shorten the film-formation time and tune the size of the polymer aggregates and SMA crystallites, to form bicontinuous networks in the active layer. As a result, this two-step heating strategy endows the film with improved charge generation, transport, and collection and thus a much higher device efficiency (ca. 4.6 times of that for the as-cast device) in comparison to those from nonoptimal solution and/or substrate temperatures. This work emphasizes the crucial role of regulating processing conditions in fabricating the nonhalogen solvent-processed high-efficiency OSCs.
Bibliographical noteFunding Information:
This work was supported by the National Natural Science Foundation of China (51773046 and 51873204), the Science and Technology Program of Shaanxi Province (2021KJXX-13), the Fundamental Research Funds for the Central Universities (GK202103104), and the School of Materials Science and Engineering, Shaanxi Normal University. H.Y.W. acknowledges financial support from the National Research Foundation of Korea (2020M3H4A3081814 and 2016M1A2A2940911).
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ASJC Scopus subject areas
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry