Plasmonic bulk heterojunction photovoltaic devices based on poly (9-vinylcarbazole)/gold nanocomposites: effect of aspect ratio of gold nanorod

A simple seeded growth method was employed to synthesize various aspect ratio gold (Au) nanorods and these nanorods were incorporated into a conducting polymer, poly (9-vinylcarbazole), PVK. A series of bulk heterojunction (BHJ) photovoltaic devices was fabricated using the nanocomposite materials as the active layer. A detailed investigation of device performance shows that the device parameters can be tuned by changing the aspect ratio of nanorods. A longer nanorod, provides larger scattering intensity, leading to a prolonged light transport path, thus increasing light absorption in the BHJ. Again, Au nanorods increase the shunt resistance and decrease the series resistance of the device that can lead to an increased value of open circuit voltage (V_oc = 0.144–0.246 V). With increase in aspect ratio more percolation pathways form inside the active layer thus facilitating the transport of electrons and photocurrent as well. Present study shows that the photo conversion efficiency of a BHJ photovoltaic device was increased from 0.29 to 1.45 % with increasing the aspect ratio of Au nanorods from 2 to 3.5.