Enhanced performance of organic photovoltaic devices by incorporation of tetrapod-shaped CdSe nanocrystals in polymer-fullerene systems

Tetrapod (TP)-shaped colloidal CdSe nanocrystals (NCs) were synthesized by a hot injection method in inert atmosphere using standard Schlenk line techniques and characterized by UVVis absorption, photoluminescence (PL), X-ray diffraction (XRD), and transmission electron microscopy. NCs with an average diameter of 4nm and an average length of 23nm have been obtained with a wurtzite crystal structure. Hybrid organic photovoltaic (OPV) devices were fabricated from ternary blends of poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl C71 butyric acid methyl ester (P3HT:PC71BM) and TP-shaped CdSe NCs at 02wt.% concentration range. The hybrid OPV devices with CdSe NCs at an optimum concentration of 1.5wt.% exhibited higher short-circuit current density (JSC) and power conversion efficiency (PCE) than the devices without NCs. This improvement has been attributed to enhanced electron transport through the TPs in the direction perpendicular to the plane of substrate.