Cyanine dye acting both as donor and acceptor in heterojunction photovoltaic devices

Abstract

The use of cyanine dyes in thin-film heterojunction photovoltaic devices is investigated. It is demonstrated that a carbocyanine dye acts as donor in conjunction with buckminsterfullerene (C60). Due to its high electron affinity, the cyanine can also act as acceptor when using copoly(dicyano-phenylvinylene-triphenylamine) as donor. H and J aggregates of the cyanine dye play a determining role both in the photocurrent spectrum and in the open circuit voltage. Open-circuit voltages ranging from 0.25 to 1.28 V are obtained for devices using the cyanine as donor and acceptor, respectively. When the cyanine layer is sandwiched between the polymer donor and the C60 acceptor, incident photon to current conversion efficiencies greater than 10% are observed. The possibility of using cyanine dyes at the same time as donors and acceptors is a promising strategy to improve conversion efficiency.