Carbon nanotube effects on electroluminescence and photovoltaic response in conjugated polymers

This letter reports the experimental results of enhanced electroluminescence (EL) and photovoltaic (PV) response upon doping single-wall carbon nanotubes (SWNTs) into conjugated polymer poly2-methoxy-5-(2′-ethylhexyloxy)-1, 4-phenylenevinylene (MEHPPV) based on single-layer light-emitting diodes. We found that the dispersed SWNTs result in two processes: charge transport and exciton dissociation at the tube-chain interface in the SWNT/polymer composites. The detailed EL and PV studies indicate that low SWNT doping concentrations mainly improve the bipolar charge injection, leading to enhanced both reverse and forward EL with reduced threshold voltage. As the SWNT doping concentration continues to increase, the interfacial exciton dissociation becomes dominated, giving rise to an increased PV response. This SWNT concentration-dependent charge transport and exciton dissociation present a pathway to individually address the dual EL and PV functionalities of SWNT-doped polymer composites by controlling the doping level of the SWNTs.