Solution Processed WO3 and PEDOT:PSS Composite for Hole Transport Layer in ITO-Free Organic Solar Cells

We developed PEDOT:PSS [poly (styrenesulfonate)-doped poly(3,4-ethylenedioxythiophene] and tungsten oxide (WO3) based hybrid thin films by facile hydrothermal method. The solution processed WO3-PEDOT:PSS hybrid thin films are fully characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV-Vis (UV), Raman, X-ray photoelectron spectra (XPS) and Brunauer-Emmett-Teller (BET) surface area analysis. XRD and SEM results suggest that WO3 has crystalline structure with monoclinic phase and spherical shaped nanoparticles (20-25 nm), which is uniformly decorated on the surface of PEDOT:PSS sheets. The value of E-g [calculated by linear extrapolating of (F(R infinity) h nu)(2) and h nu] was evaluated to be 3.11 and 2.85 eV for pure WO3 and WO3/PEDOT:PSS, respectively. The PL intensity of WO3/PEDOT:PSS is maximum lower than the pristine WO3 and PEDOT:PSS, implying an improved interfacial contact quality at the WO3/PEDOT:PSS. Photovoltaic performance of WO3-PEDOT:PSS devices were measured under AM 1.5 G 1 sun light intensity of 100 mW/cm(2). Organic solar cell devices with WO3-PEDOT:PSS layer give rise to a significant increase in J(SC) from 9.35 +/- 0.03 to 16.2 +/- 0.01 mA/cm(2) respectively and in V-OC from 0.28 V to 0.72 V respectively, resulting in a remarkable PCE increase from 0.592 +/- 0.03 to 0.714 +/- 0.02%. The WO3/PEDOT:PSS composite deliver a PCE of 7.81 +/- 0.01%. The superior performance of WO3/PEDOT:PSS composite was attributed to the reduced current leakage, enhanced hole extraction characteristics, and less trap-assisted interfacial recombination via current density-voltage.

Automated summary

PEDOT:PSS and WO3 hybrid thin films were successfully prepared using a hydrothermal method. The films were characterized and used to fabricate photovoltaic devices, which exhibited improved performance.