Preparation of efficient oligomer-based bulk-heterojunction solar cells from eco-friendly solvents

The field of solution-processable oligomer-based organic solar cells is progressing rapidly. However, common halogenated solvents used in the fabrication of solar cell devices stand out as a growing problem concerning industrial applications. Here, we report on the fabrication and post-treatment of solution-processed bulk heterojunction solar cells exclusively from non-halogenated solvents o-xylene for processing and tetrahydrofuran for solvent vapor annealing (SVA). As donors, we incorporated a series of three different dithieno[ 3,2-b:2',3'-d] pyrrole (DTP) containing A-D-A co-oligomers and [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) as acceptor. The resulting devices exhibited power conversion efficiencies (PCEs) of up to 7.04%. The photoactive layers were probed using absorption spectroscopy, grazing incident X-ray diffraction (GIXRD), and atomic force microscopy (AFM) to clarify the effect of the solvent vapor treatment.