Flexible PEDOT: PSS/ITO hybrid transparent conducting electrode for organic photovoltaics

In order to improve the performance and mechanical flexibility of the transparent conducting electrodes (TCEs) for organic photovoltaics, we proposed a flexible PEDOT:PSS/ITO hybrid TCE. A conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was introduced as a buffer layer beneath the ITO film. This PEDOT:PSS/ITO hybrid electrode showed a sheet resistance of 85 Ω/sq, which was much better than that of a single-layer ITO film. The mechanical integrity of the flexible PEDOT:PSS/ITO hybrid electrode was investigated by bending and fragmentation tests. The failure bending radius was lower in bending tests of the PEDOT:PSS/ITO electrode than for the ITO electrode due to buffering effect of PEDOT:PSS film. A fragmentation test showed superior stretchability and better interfacial adhesion strength for the PEDOT:PSS/ITO hybrid electrode on a PET substrate than for the ITO electrode. We have prepared flexible organic photovoltaic (OPV) devices using the PEDOT:PSS/ITO hybrid TCE. The flexible OPV device fabricated using the PEDOT:PSS/ITO hybrid anode exhibited a power conversion efficiency of 3.21% (FF=0.45, Voc=0.72 V), which is comparable with that using an ITO anode. A bending test of the OPV device also showed better mechanical bending and crack-resistance performances for the OPV device with the PEDOT:PSS/ITO hybrid anode than for the ITO anode. The comparable performance and superior flexibility of flexible OPVs with an PEDOT:PSS/ITO hybrid anode indicates that the PEDOT:PSS/ITO hybrid electrode is a promising flexible electrode scheme for next generation flexible photovoltaic devices.