Indium-free flexible perovskite solar cells with AZO/Cu/Ag/AZO multilayer transparent electrodes

Flexible perovskite solar cells (PSCs) fabricated on plastic substrates have great potential applications in numerous emerging fields such as portable/wearable electronics, automobiles, and flying objects due to their high efficiency, low cost, and light weight. However, most of the reported flexible PSCs based on plastic substrate use expensive and fragile ITO as transparent electrodes, resulting in significant performance degradation after continuous bending. Here, we develop an indium-free AZO/Cu/Ag/AZO multilayer transparent electrode deposited on PET by magnetron sputtering technique and utilize it to fabricate of flexible PSCs. It is demonstrated that predepositing an ultrathin Cu layer on the AZO layer can significantly reduce the permeation threshold of the subsequent grown Ag layer, thereby improving the optoelectronic properties of the deposited multilayer transparent electrode. The highest figure of merit value of 3.8 × 10−2 Ω−1 was obtained for the AZO(40 nm)/Cu(0.1 nm)/Ag(7 nm)/AZO (40 nm) electrode, which has an average relative optical transmittance in the visible light range (400–800 nm) of 90.77 % and sheet resistance of 9.9 Ω/sq. The flexible PSCs based on the optimized AZO/Cu/Ag/AZO electrode achieve power conversion efficiency (PCE) of 14.68 %. Moreover, they can maintain 90 % of the initial PCE even after 5000 bending cycles at a bending radius of 8 mm.