Highly transparent vanadium oxide-graded indium zinc oxide electrodes for flexible organic solar cells

• Transparent and flexible V2O5 graded IZO (VGIZO) electrodes.
• High work function of VGIZO electrodes
• The VGIZO film is a promising flexible anode for flexible organic solar cells.

We investigated characteristics of amorphous V2O5-graded InZnO (IZO) films to use as a flexible anode for flexible organic solar cells (FOSCs). Graded sputtering of the V2O5 layer on the IZO layer produced V2O5-graded IZO anodes (VGIZO) with a sheet resistance of 42.14 Ω/square, a resistivity of 6.32 × 10− 4 Ω cm, and an optical transmittance of 82.15%, as well as good mechanical flexibility. In addition, the VGIZO electrode showed a greater work function of 5.2 eV than that (4.9 eV) of an IZO anode, which is beneficial for hole extraction from an organic active layer. Due to the higher work function of the VGIZO electrodes, FOSCs fabricated on the flexible VGIZO anode exhibited a higher power conversion efficiency 2.753% than that of FOSCs on the IZO anode. This indicates that the V2O5 graded sputtering is a promising technique to increase the work function of the IZO anode without change in sheet resistance and transmittance.