Vertically Aligned Carbon Nanotubes for Organic Photovoltaic Devices

Abstract

As promising thin-film photovoltaic (PV) devices, organic solar cells offer many advantages, including low-cost, lightweight, large-area processability, and versatility for applications. Recently developed heterojunction device structure can support a highly efficient photoinduced charge transfer (exciton dissociation) at the junction between electron-donating and -accepting materials, leading to a high photocurrent quantum efficiency (QE) up to 70%. The device performance, however, is currently limited by the low light absorption, poor carrier transport, and degradation of the materials. As reviewed in this chapter, dispersed heterojunction devices containing vertically aligned carbon nanotubes (VA-CNTs) can show improved carrier transport properties, as each of constituent aligned CNT is connected directly onto an electrode to maximize the electron mobility. The hole transportation can also be improved by electrochemical or chemical vapor deposition of appropriate conjugated polymers onto the individual VA-CNT to provide a well-controlled conjugation path and phase morphology. The recent advances in the synthesis of VA-CNTs and new photovoltaic-active polymers for the fabrication of conjugated polymer/CNT dispersed hetero-junction solar cells, will be summarized in this chapter to provide a blueprint for the development of high efficiency organic solar cells with the new heterojunction architecture containing VA-CNTs.