Influence of PEDOT:PSS buffer layer on the performance of organic photocoupler

We have fabricated an organic photocoupler with organic light-emitting diodes (OLEDs) with 520 nm emissive wavelength as the input light source and a photodiode (PD) based on poly(3-hexylthiophene) (P3HT):1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)-C₆₁ (PCBM) as the detector. The influences of buffer layer (PEDOT:PSS) on output current (I_out), current transfer ratio (CTR) and time response characteristics of the photocoupler device were studied. Through our experiments, It is found that the output current linearly increases with the input current, the max output current and CTR of the devices with PEDOT:PSS buffer layer are 2 times and 7 times than that of the devices without buffer layer respectively, which show that the existence of buffer layer can enhance the output photocurrent efficiently. Moreover, the existence of PEDOT:PSS eliminates the time delay of the devices.