Investigation of Triple Symmetric Non-halogen Benzene Derivative Solvent for Spray-Coated Polymer Solar Cells

Abstract

The performance of spray-coated polymer solar cells could be largely improved via morphologies and phase optimization by solvent engineering. However, there is still a lack of fundamental knowledge and know-how in controlling blend morphology by using various solvents. Here, the effect of adding low polar benzene and non-halogen benzene derivatives with triple symmetric molecular has been systematically investigated and discussed. It is found that the triple symmetric non-halogen benzene could promote the formation of preferential face-on molecule orientation for PBDB-T-2Cl:IT4F films by grazing incidence wide-angle X-ray scattering. The X-ray photoelectron spectroscopy shows that PBDB-T-2Cl could be transported to the surface of the blend film during drying process. A 3D opt-digital microscope shows that triple symmetric non-halogen benzene could also improve the morphologies of active layers by reducing the coffee ring or other micro-defects. Due to the appropriate vapor pressures, devices with mixing 20% benzene or the triple symmetric non-halogen in spray solution could significantly improve the device performance. Device prepared using 20% 1,3,5-trimethylbenzene (TMB) and 80% chlorobenzene (CB) mixture solvent has the best morphology and phase structure, and the power conversion efficiency (PCE) of the device was increased nearly 60 to 10.21% compared with the device using CB as the only solvent.

Improving Performance of Organic Photovoltaic Devices under Low Illuminations

“…To minimize the presence of trap states, it is necessary to reduce the density of structural defects in the active layer of OPV devices. This requires a careful optimization of the stacking properties of organic molecules in the active layer. , Existing studies have demonstrated that the use of high-boiling-point solvents with a lower evaporation rate is an effective approach to achieve a more desired molecular stacking structure, thereby reducing the density of structural defects. − For instance, Hu et al reported that compared to low-boiling-point carbon disulfide solvents, the utilization of high-boiling-point ortho-dichlorobenzene as a processing solvent for P3HT:PCBM active layers allows sufficient time for self-organization during a gradual drying process, resulting in less structural defects and the formation of the optimal active layer morphology . Therefore, to mitigate the influence of trap-assisted recombination, limiting the performance of OPV devices under low illumination intensities, we intend to employ a commonly used high-boiling-point solvent for device fabrication.…”