Effect of Gold Nanospheres and Nanodots on the Performance of PEDOT:PSS Solar Cells.

Abstract

Gold nanospheres were synthesized using a modified Turkevich method (d = 14±4 nm, λmax = 531 nm), while gold nanodots made of spheres (5±2 nm) and non-spherical nanodots (aspect ratio of 1.7±0.4) were synthesized using a modified seed mediated method. The spherical gold nanodots exhibited a transverse excitation mode at 525 nm while the non-spherical gold nanodots showed an additional longitudinal excitation mode observed in the UV-vis spectrum at 794 nm. The gold nanodots also exhibited a surface enhanced Raman effect which significantly influenced the electronic properties of the photovoltaic device. The incorporation of Au nanospheres in a PEDOT:PSS hole transport layer increased the photovoltaic device efficiency by 51%. This was attributed to a decrease in the series resistance which improved the hole transport pathways in the PEDOT:PSS and enhanced the current density of the photovoltaic device. In contrast, incorporation of spherical and non-spherical gold nanodots into the PEDOT:PSS hole transport layer resulted in a decrease in current density and a consequent decrease in efficiency. This can be attributed to the electron-hole recombination and accumulation of space charges by the non-spherical gold nanodots in PEDOT:PSS resulting in an increased series resistance and leakage currents and hence a reduced device performance. Thus, the morphological, structural and opto-electrical properties of the gold nanospheres and nanodots influenced the device performance of the PEDOT:PSS solar cells.