Organic solar cells using few-walled carbon nanotubes electrode controlled by the balance between sheet resistance and the transparency

Organic photovoltaic devices (OPD) using high conductive transparent few-walled carbon nanotubes (FWNT) film prepared by spraying was fabricated as a selective hole collection. Photovoltaic response with different sheet resistance $(Rs)$ and the transparency $(T)$ of FWNT film was investigated. Maximum efficiency of OPD up to 0.61% with the structure of FWNT (⁠$T=70%$⁠, $Rs=86Ω/◻$⁠)/poly(3-hexylthiophene): [6-6]phenyl-$C61$-butyric acid methyl ester/Al demonstrates a promising alternative of ITO (0.68%) with almost identical operation. The performance improvement results from the optimal balance between sheet resistance and transparency with three-dimensional network interface between nanotubes and polymers.