Binary Nonchlorinated and Nonaromatic Solvent -Processed PTB7:PC71BM and PTB7-Th:PC71BM Active Layers Showing Efficiency Comparable to that of Chlorobenzene in Organic Solar Cells

For the eventual commercialization of solution processed organic solar cells (OSCs), using a nonaromatic and nonchlorinated solvent of low toxicity is highly desirable. In this work, 1,4-dioxane (DIOX) as a new nonaromatic and non chlorinated solvent and its mixing with terpinolene (TPO) to form a binary nonaromatic and nonchlorinated mixture were introduced to process PTB7:PC71BM and PTB7-Th:PC71BM bulk-heterojunction (BHJ) active layers for conventional and inverted OSCs, and compared with chlorobenzene (CB). Despite the poor film forming with DIOX as the solvent, a DIOX/TPO (58:42) mixture as the solvent is optimal to afford high-quality BHJ blend films. As a result, the DIOX/TPO (58:42) mixture-processed PTB7:PC71BM and PTB7-Th:PC71BM active layers showed power conversion efficiencies of 7.6 and 8.3%, respectively, in the conventional OSCs and the efficiency could be elevated to 8.30 and 9.39% in inverted OSCs, respectively. All of the photovoltaic performances are comparable to those of the CB cases. Our results suggest that the mixing of some nonchlorinated and nonaromatic solvents is an attractive strategy to expand valuable solvents toward the environment-friendly fabrication of OSCs.