Enhanced performance and stability of polymer BHJ photovoltaic devices from dry transfer of PEDOT:PSS

Polymer solar cells with enhanced initial cell performances and long-term stability were fabricated by performing a simple dry transfer of a hole extraction layer [poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)] onto an indium tin oxide (ITO) substrate. Due to the very flat surface of the polyurethane acrylate/polycarbonate (PUA/PC) film, which was used as a mold and resembled the surface of the original substrate (silicon wafer), the transferred layer had a very smooth surface morphology, resulting in enhancement of the interfacial characteristics. The work function of the PEDOT:PSS layer and the morphology of bulk hetero junction (BHJ) layer were tuned by controlling the position of PSS enrichment in the PEDOT:PSS layer using the dry transfer. The power conversion efficiency of PTB7:PC₇₁BM BHJ device prepared by the dry transfer was 8.06 %, which was significantly higher than that of the spin-cast device (7.32 %). By avoiding direct contact between the ITO substrate and the PEDOT:PSS solution in the dry transfer system, etching and diffusion of indium in the ITO substrate were greatly reduced, thereby improving the stability. Smoothing it over with a stamp: Bulk-heterojunction polymer solar cells with enhanced device performances and a long-term stability are fabricated using a simple dry transfer method. Due to the reverse poly(styrenesulfonate) (PSS)-enriched region in the transferred poly(3,4-ethylenedioxythiophene (PEDOT):PSS layer, its work function and morphology can be tuned. Furthermore, by avoiding direct contact between substrate and PEDOT:PSS solution, the stability is improved.