TCO-free flexible organo metal trihalide perovskite planar-heterojunction solar cells

In this work we present a transparent conductive oxide (TCO)-free flexible perovskite planar heterojunction solar cell made with a semitransparent anode realized with a highly conductive poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) PEDOT:PSS (PH1000 by Clevios) modified with ethylene glycol layer, deposited via spray coating. We investigated several formulations of PEDOT:PSS modified by addition of solvents with high boiling point such as ethylene glycol (EG) and dimethyl sulfoxide (DMSO). Optimized samples show a 65% transmittance at 550 nm and a sheet resistance of 28 Ω/□. On these optimized electrodes we fabricated a TCO-free flexible device, the best of which exhibited a power conversion efficiency of 4.9% under 100 mW/cm2 illumination at AM1.5G. The efficiency of the perovskite planar-heterojunction solar cell, with the modified PEDOT:PSS anode was comparable to the one realized on a PET-ITO anode. Moreover, in the bending test, ITO-free flexible solar cell manifested superior mechanical robustness, showing the high flexibility of the perovskite layer.