Organic photovoltaic devices from discotic materials

Disk-shaped molecules can be self-assembled into columns, which may exhibit one-dimensional charge transporting properties within well-oriented domains. They are promising materials to choose in fabrication of organic photovoltaic device and to improve photovoltaic responses. In this work, a discotic triphenylene derivative 2,3,6,7,10,11-hexapentyloxytriphenylene (HAT5) was investigated and used in fabrication of organic photovoltaic devices. The device have a double-layered structure of ITO/HAT5/PTCDI-C13/Al, in which HAT5 acts as an acceptor and hole transporting layer and N,N'-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13) acts as a donor and electron transporting layer. The device demonstrated an open circuit voltage up to 0.7V, which depended strongly on the thickness of the PTCDI-C13 layer. Function of organic/organic interface to the generation of photovoltaic effect was observed experimentally through a comparison of device made with HAT5 layers of different molecular arrangement. A higher ordered morphology obtained through annealing led to a substantial improvement in the fill factor of the device. A distinct change in open circuit voltage was also observed upon the molecular orientation though it was not what we anticipated. This work demonstrated a useful route to tune the performance of photovoltaic response of organic devices through manipulating molecular orientation and organization in the device.