Effective light trapping enhanced near-UV/blue light absorption in inverted polymer solar cells via sol–gel textured Al-doped ZnO buffer layer

• Sol–gel derived AZO films with flat and textured morphologies were used as cathode buffer layers for inverted polymer solar cells.
• The textured-AZO together with reflective back electrode provides efficient light-trapping inducing further light absorption in active layer at the near-UV/blue light region.
• The textured-AZO devices show 18.7% and 17.6% enhancement in short circuit current density and efficiency, respectively, compared with the flat-AZO devices.

The effects of sol–gel textured Al-doped ZnO (AZO) cathode buffer layer on the performance of the inverted polymer solar cells have been investigated in this work. Textured AZO, together with a reflective back electrode provides efficient light-trapping, inducing further light absorption in the active layer. The AZO films were characterized with respect to their morphology, optical and electrical properties. Due to the enhanced absorption at near-UV/blue light region (300–500 nm), the short current density of the textured-AZO device is increased from 9.52 to 11.30 mA/cm2 compared with the reference cell based on the flat-AZO. Power conversion efficiency is increased substantially from 2.44% to 2.87% since without loss in the fill factor and open circuit voltage.

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