Shape control of plasmonic gold nanoparticles and its application to vacuum-free bulk hetero-junction solar cells

The plasmonic gold (Au) nanoparticles (NPs) with different shapes were synthesized and characterized. The Au nanospheres (NSPs) had a size of ~ 7 nm, while the Au nanorods (NRs) had a size of ~ 7 nm of width and ~ 23 nm of length, which were measured from electron transmission spectroscopy (TEM) technique. The Au NPs with different shapes were incorporated into the hole transport layer (HTL) of solar cell device, which led to improving light absorption and scattering of photoactive layer, eventually leading to the increase of device performance. The surface morphology of device’s active layer was optimized by deposition of 20 nm thin ZnO buffer layer between the active layer and the electrode. Finally, the device with the structure of glass/indium tin oxide (ITO)/(polyethylene dioxy thiophene doped with polystyrene-sulfonic acid (PEDOT:PSS) + Au NRs)/active layer/zinc oxide (ZnO)/E-GaIn showed a power conversion efficiency (PCE) of ~ 6%.