Well-designed poly(3-hexylthiophene) as hole transporting material: A new opportunity for solid-state dye-sensitized solar cells

- Power conversion efficiency of 4.78% was reached with P3HT vs. 3.99% with spiro-OMeTAD after annealing.
- Annealing reduces the intrinsic trap-limited charge transport occurring in neat P3HT.
- Well-defined P3HTs (high regioregularity, medium-range molecular weight, narrow dispersity) are alternatives to spiro-OMeTAD.

All solid-state dye-sensitized solar cells (ss-DSSCs) based on the reference D102 organic dye and using poly(3-hexylthiophene) (P3HT) as hole transporting material were fabricated and compared to the most used 2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). Power conversion efficiency of 4.78% was reached with P3HT vs. 3.99% with spiro-OMeTAD, which emphasizes that polythiophene derivatives remain serious alternatives to spiro-OMeTAD for efficient and low-cost photovoltaic energy conversion. Here, P3HT combining high regioregularity, medium-range molecular weight and narrow dispersity was targeted. The ability of those P3HT chains to form semicrystalline domains upon annealing leads to improved hole mobility, photocurrent collection and thus, device performance.

Highly regioregular P3HT with narrow dispersity allow achieving high PCEs up to 4.78% (vs. 3.99% for Spiro-OMeTAD) after annealing.76