The impact of TiO2 nanostructures on the physical properties and electrical performance of organic solar cells based on PTB7:PC71BM bulk heterojunctions

Abstract

Hybrid organic solar cells based on pairs of donor and acceptor materials offer enhanced light absorption width and surface morphology. In order to investigate the role of introducing metal oxide nanoparticles (NPs) and thermal annealing on the optical, structural and morphological behaviours of the active layer polymers’ [poly([4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}):[6,6]-Phenyl-C71-butyric acid methyl ester (PTB7:PC71BM), thin films with and without the addition of 10% TiO2 nanoparticles (NP) were prepared and characterized. Ultraviolet–Visible- Near-infrared (UV–Vis-NIR) Spectrophotometry, Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) techniques were used to characterize the thin films. Results show that incorporation of the TiO2 (NPs) with annealing treatment of the thin films enhanced the optical absorption and crystallinity of the PTB7:PC71BM blend. The device based on PTB7:PC71BM showed power conversion efficiency (PCE) of 5.6%. The incorporation of 10%-TiO2 into the PTB7:PC71BM blend leads to a sharp drop in PCE (0.08%).