Non-Halogenated Solvent-Processed High-Efficiency Polymer Solar Cells: the Role of Diphenyl Ether in Morphology, Light-Trapping, Transport Properties

There is an urgent need to use green non-halogenated solvents to prepare polymer solar cells (PSCs) for industrialization. It is time-consuming but necessary to find a suitable non-halogenated solvent/additive combination for a given donor:acceptor materials system. In this research, we report a non-halogenated binary solvent system toluene/diphenyl ether (DPE) for the PBDTT-DTffBT:PC 71 BM and PM6:Y6 blending systems that exhibit comparable power conversion efficiency (PCE) to that of devices prepared with halogenated solvents. The nanoscale morphology indicates that blending film processed solely with toluene has poor phase segregation and a rough surface, which hinders charge separation and interfacial contact. Besides, the total absorption spectra revealed significant light-trapping losses in the toluene-processed solar cells, resulting in low photocurrent generation. DPE incorporation addresses these issues and significantly improves the short-circuit current density and fill factor. Moreover, non-halogen solvent-processed devices exhibit high hole mobility and low transporting impedance properties. The present study enriches the families of eco-friendly, high-efficiency PSCs fabricated using non-halogenated solvents. Graphical Abstract