Development of Carbazole Dyes for Efficient Molecular Photovoltaics

Abstract

Dye–Sensitized Solar Cells (DSSCs), which are one of the promising molecular photovoltaics, have been attracting considerable attention because the unconventional solar cells exhibit high performance and have the potential for low–cost production. The photosensitizer is one of the most important components influencing solar–cell performance, because the choice of sensitizer determines the photoresponse range of the DSSC and initiates the primary steps of photon absorption and the subsequent electron transfer process. Generally, Ru–polypyridyl–complex sensitizers, developed by Prof. Gratzel and co–workers, have been employed for efficient DSSCs. In addition to conventional Ru–complex sensitizers, metal–free organic dyes have also been utilized as sensitizers in DSSCs, and the photovoltaic performance of DSSCs based on organic–dye sensitizers has been improved relative to earlier studies of DSSCs with organic dyes. We have designed and synthesized alkyl–functionalized carbazole dyes to improve both solar–cell performance and long–term stability of the solar cells. Here, we report detailed synthesis of carbazole dyes, photovoltaic performance and long–term stability of DSSCs based on these carbazole dyes.