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

Abstract

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 nonchlorinated 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.

Eco-Friendly Polymer Solar Cells: Advances in Green-Solvent Processing and Material Design

“…For example, high-performance PTB7-Th:PC 71 BM devices (PCE = 9.39%) were fabricated with the optimal ratio of non-halogenated 1,4-dioxane and terpinolene solvents (58:42 v/v) as predicted by the low R a and RED values. 42 The PSCs not only showed similar performance to the CBprocessed counterparts, but also dramatically improved the efficiency of the PSCs processed from the single 1,4-dioxane solvent (PCE ≈ 0.01%). Similarly, with the help of the HSPs, another system based on PCDTBT:PC 71 BM achieved a PCE of 6.75% using a mixture of CS 2 and acetone (70:30 v/v) which even outperformed the devices processed from CB (PCE = 5.80%).…”

“…The aforementioned empirical evaluation can be significantly strengthened through quantitative prediction of the solubilities using the Hansen solubility parameters (HSPs), as demonstrated in various eco-friendly PSC studies. ,− The HSPs are δ D , δ P , and δ H , which represent dispersive interactions, permanent dipole–dipole interactions, and hydrogen bonding interactions, respectively. The HSPs of a material can be plotted in a 3-dimensional space (Hansen space) where δ D , δ P , and δ H correspond to the x , y , and z axes, respectively.…”

“…Furthermore, the Hansen theory can be applied to find a proper green co-solvent (green solvent–green solvent) pair and its optimal volume ratio to enhance the solvent quality and, thus, the photovoltaic performance. ,,, There are two requirements for the selection of a proper green-solvent combination: (i) the solvents which make up the mixture should be miscible with each other, and (ii) the volume ratio of each solvent should be fine-tuned to optimize the solubility of photoactive materials. Under this principle, there have been several attempts to obtain a suitable green co-solvent by using the HSPs.…”

“…Under this principle, there have been several attempts to obtain a suitable green co-solvent by using the HSPs. For example, high-performance PTB7-Th:PC 71 BM devices (PCE = 9.39%) were fabricated with the optimal ratio of non-halogenated 1,4-dioxane and terpinolene solvents (58:42 v/v) as predicted by the low R a and RED values . The PSCs not only showed similar performance to the CB-processed counterparts, but also dramatically improved the efficiency of the PSCs processed from the single 1,4-dioxane solvent (PCE ≈ 0.01%).…”

Designing Nonfullerene Acceptors with Oligo(Ethylene Glycol) Side Chains: Unraveling the Origin of Increased Open‐Circuit Voltage and Balanced Charge Carrier Mobilities

“…To evaluate the photovoltaic performance of the NIDCS acceptors, OSC devices were fabricated with a configuration of ITO/PEDOT : PSS/PTB7 : NIDCS acceptor/Ca/Al. We chose PTB7 as a donor for the OSC devices in this study because PTB7 had shown higher performance with better morphology formation in high‐boiling point solvents such as chlorobenzene than in non‐aromatic solvents [22,23] . However, in our previous study, [16] due to the low solubility of NIDCS‐HO in the aromatic solvents, we had to fabricate its OSC device with PTB7 using chloroform, which led to a low PCE (∼3.53 %).…”