Nature‐inspired light‐harvesting liquid crystalline porphyrins for organic photovoltaics

Abstract

A new class of nanoscale light‐harvesting discotic liquid crystalline porphyrins, with the same basic structure of the best photoreceptor in nature (chlorophyll), was synthesized. These materials can be exceptionally aligned into a highly ordered architecture in which the columns formed by intermolecular π–π stacking are spontaneously perpendicular to the substrate. The homeotropic alignment, well confirmed by synchrotron X‐ray diffraction, could not only provide the most efficient pathway for hole conduction along the columnar axis crossing the device thickness, but also offer the largest area to the incident light for optimized light harvesting. Their preliminary photocurrent generation and photovoltaic performances were also demonstrated. The results provide new and efficient pathways to the development of organic photovoltaics by using homeotropically aligned liquid crystal thin films.

Keywords:

• nature‐inspired liquid crystals
• light‐harvesting porphyrin
• hexagonal phase
• homeotropic alignment
• photovoltaics

Acknowledgements

This work was supported, in part, by LCI, an Ohio Board of Regents’ Research Challenge award, AFOSR (FA9550‐06‐1‐0384) and National Science Foundation grant DMR‐0637221. Use of the Advanced Photon Source (APS) was supported by the US Department of Energy (DOE), Basic Energy Sciences (BES), Office of Science, under Contract No. W‐31‐109‐Eng‐38. The Midwestern Universities Collaborative Access Team’s (MUCAT) sector at the APS is supported by the US DOE, BES, Office of Science, through the Ames Laboratory under Contract No. W‐7405‐Eng‐82.