A transparent poly(3,4-ethylenedioxylenethiophene):poly(styrene sulfonate) cathode for low temperature processed, metal-oxide free perovskite solar cells
Low temperature processed, metal-oxide free planar perovskite solar cells (PSCs) were fabricated on glass and polyethylene terephthalate (PET) substrates using polyetherimide (PEI) modified poly(3,4-ethylenedioxylenethiophene):poly(styrene sulfonate) (PEDOT:PSS) as the cathode. The modification by PEI significantly changed the work function of PEDOT:PSS from −5.06 to −4.08 eV, yielding better electron transportation. The rigid cell on the glass substrate exhibited a high power conversion efficiency (PCE) of 12.42% without significant hysteresis and comparable to the PCE of PSCs with metal oxide cathodes. Moreover, the stability in air was higher by 32% than that of the devices with metal-oxide cathodes. The flexible device on the PET substrate exhibited a PCE of 9.73% and good bendability. Our results indicate that the flexibility of the PEDOT:PSS/PEI cathode is promising for use in large-scale roll-to-roll production of PSCs.