Enhanced performances of hybrid polymer solar cells with p-methoxybenzoic acid modified zinc oxide nanoparticles as an electron acceptor

Enhanced performances of hybrid polymer solar cells based on a blend of poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and p-methoxybenzoic acid (MBA) modified zinc oxide (ZnO) nanoparticles were reported. Both the short-circuit current and open-circuit voltage of solar cells were improved by using MBA modified ZnO nanoparticles as electron acceptor. The overall power conversion efficiency was increased from 1.09% to 1.52% under AM 1.5 G 100 mW/cm2 illumination after ZnO was modified with MBA at 0.1 wt.%. It was found that modification of ZnO with 0.1 wt.% of MBA did not affect electron and hole transport properties of the active layer. However, a fine phase separation between MEH-PPV donor and MBA-modified ZnO acceptor was obtained. The fine phase separation enhanced the exciton dissociation efficiency and hence the power conversion efficiency of solar cells.

The challenge for ZnO nanocrystal-based hybrid polymer solar cells lies in large phase separation between polymer and ZnO due to the high surface polarity of ZnO which results its poor compatibility with conjugated polymer. It is well solved by surface modification of ZnO nanocrystals with p-methoxybenzoic acid (MBA). The methoxyl group in MBA molecule renders the ZnO surface more hydrophobic which favors well dispersion of ZnO in MEH-PPV matrix. Consequently, a nanoscale phase separation is realized in MEH-PPV:ZnO blend film by using MBA-modified ZnO nanocrystals as an electron acceptor and the power conversion efficiency of the resulted hybrid polymer solar cell is increased up to 50% compared to the solar cell based on as-prepared ZnO nanocrystals.Figure optionsDownload as PowerPoint slideResearch highlights
► The ZnO surface becomes more hydrophobic by MBA surface modification.
► A fine phase separation between MEH-PPV and MBA-modified ZnO is obtained.
► Electron transport between ZnO aggregates is not influenced by MBA modification.
► Hole transport in MEH-PPV domains is reduced with high content of MBA.