Highly conductive and transparent carbon nanotube-based electrodes for ultrathin and stretchable organic solar cells**Project supported by the National Basic Research Program of China (Grant No. 2012CB932302), the National Natural Science Foundation of China (Grant Nos. 11634014, 51172271, 51372269, and 51472264), and the “Strategic Priority Research Program” of the Chinese Academy of Sciences (Grant No. XDA09040202).

Abstract

In this work, we have presented a freestanding and flexible CNT-based film with sheet resistance of 60 Ω/□ and transmittance of 82% treated by nitric acid and chloroauric acid in sequence. Based on modified CNT film as a transparent electrode, we have demonstrated an ultrathin, flexible organic solar cell (OSC) fabricated on 2.5-μm PET substrate. The efficiency of OSC, combined with a composite film of poly (3-hexylthiophene) (P3HT) and phenyl-C61 butyric acid methyl ester (PCBM) as an active layer and with a thin layer of methanol soluble biuret inserted between the photoactive layer and the cathode, can be up to 2.74% which is approximate to that of the reference solar cell fabricated with ITO-coated glass (2.93%). Incorporating the as-fabricated ITO-free OSC with pre-stretched elastomer, 50% compressive deformation can apply to the solar cells. The results show that the as-prepared CNT-based hybrid film with outstanding electrical and optical properties could serve as a promising transparent electrode for low cost, flexible and stretchable OSCs, which will broaden the applications of OSC and generate more solar power than it now does.