Vertical orientation of copper phthalocyanine in organic solar cells using a small molecular weight organic templating layer

Ultrathin film material templating layers that force the morphology of subsequently grown electrically active thin films have been found to increase the performance of small molecule organic photovoltaic (OPV) cells. Here, we show that the electron-transporting material, hexaazatriphenylene-hexacarbonitrile (HAT-CN) can be used as a templating material that forces the copper phthalocyanine (CuPc) donor molecule to assume a vertical-standing morphology when deposited onto its surface on an indium tin oxide (ITO) electrode. For a device with HAT-CN as the templating buffer layer, the fill factor and short circuit current of CuPc:C60 OPVs were both significantly increased compared with cells lacking the HAT-CN template. This is explained by the reduction of the series resistance due to the improved crystallinity of CuPc grown onto the ITO surface.