Enhancing the performance of polymer solar cells using solution-processed copper doped nickel oxide nanoparticles as...

Polymer solar cells (PSCs) are considered promising energy power suppliers due to their light weight, printability, low-energy fabrication and roll-to-roll processability. Recently, the solution-processed NiO_x nanoparticles have been a desirable interfacial material for hole transport in the PSCs, instead of organic semiconductors. However, pure NiO_x films restrain the high performance of PSCs due to their poor electrical characteristics caused by the localized orbital distribution at the top of valence band. Therefore, metal ion doping has been explored as a method to endow NiO_x nanoparticles with the appropriate electrical characteristics. Herein, we applied solution-processed Cu-doped NiO_x (Cu:NiO_x) nanoparticles as an efficient hole transport layer (HTL) in PSCs. The Cu-doped NiO_x enhanced the electrical conductivity of the material and improved the interface contact with the active layer, which remarkably facilitated the hole extraction and effectively suppressed the carrier recombination at the interface. Thus, a higher power conversion efficiency of 7.05%, corresponding to an approximately 30% efficiency improvement compared with that of a pristine NiO_x interlayer (5.44%) in poly[N- 9''-hepta-decanyl-2,7-carbazolealt-5,5-(4',7'-di-2-thienyl-2',1',3'-ben-zothiadiazole)]:[6,6]-phenyl-C₇₁-butyric acid methyl ester (PCDTBT:PC₇₁BM)-based PSCs, was achieved by the proposed device. The developed solution-processed Cu:NiO_x nanoparticles may be an excellent alternative for interfacial materials in PSCs or other optoelectronic devices requiring HTLs.