Efficient and ultraviolet durable inverted polymer solar cells using thermal stable GZO-AgTi-GZO multilayers as a transparent electrode

The optical and electrical properties of GZO/AgTi/AZO (GATG) multilayer transparent conducting films fabricated by magnetron sputtering method were investigated. The sheet resistance and maximum optical transmittance of GATG films are 5 Ω/sq and 86%, respectively. The sheet resistance of GATG still retains stable under annealing at 400 °C, which shows better thermal stability compared to GZO/Ag/AZO (GAG) film. The enhanced thermal stability of GATG is attributed to the formation of TiO_X in Ti doped Ag nanostructure film, which can inhibit Ag atom diffusion and aggregation. PTB7-TH:PC₇₁BM based inverted polymer solar cells (PSCs) with GATG electrode gave PCE of 9.20%, which is comparable to PCE (9.23%) of the control PSCs with ITO electrode. The PCE of PSCs with GATG and ITO electrodes respectively remain 59% and 23% of the original PCE values after UV exposure for 20 min with relativize humidity of 68% in air, indicating that PSCs with GATG show better UV durability. Our results suggest that GATG as an alternative to ITO electrode can obtain efficient inverted PSCs and have stronger anti-UV ability due to its low UV transparency.