Strategic Design of Three-Dimensional (3D) Urchin-Like Pt-Ni Nanoalloys: How This Unique Nanostructure Boosts the Bulk Heterojunction Polymer Solar Cells Efficiency to 8.48%

In this study, a simple and systematic shape-controlled synthetic protocol for tailoring nanoscale structures to generate large and monodispersed of three-dimensional (3D) urchin-like Pt-Ni multipods (MPs) and spherical nanoparticles (NPs) is reported, for which the mechanism of production is elaborated in detail. We then demonstrate, for the first time, that the 3D urchin-like Pt-Ni MPs possess good solution processability and substantially enhance both short-circuit current density (Jsc) and fill factor (FF) and consequently increase the overall power conversion efficiencies (PCEs), because of the combination of multiple scattering processes of incident light, improved conductivity, and facilitating the charge transport in the active layer. PSC fabricated using 5% Pt-Ni MPs embedded in a blend of poly{[4,8-bis(2-ethyl-hexyl-thiophene-5-yl)-benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-alt-[2-(2'-ethyl-hexanoyl)-thieno[3,4-b]thiophen-4,6-diyl]} (PBDTTT-C-T) and [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) leads to compelling device PCEs of 8.48%, in comparison to 7.38% of the reference device (PBDTTT-C-T:PC71BM, fabricated and tested under the same conditions). This study thus demonstrates a novel approach to enhance the photovoltaic performance, in combination with 3D urchin-like nanoalloys.