Sensitizers with rigidified-aromatics as the conjugated spacers for dye-sensitized solar cells

Abstract

Metal-free dye sensitized solar cells emerged as an important source of a renewable energy resource because of low production, a simple fabrication process and a wide availablility of organic dyes. This review mainly focuses on metal-free sensitizers having rigidifed-aromatics as the conjugated spacers for application in DSSCs. Based on their structures dyes have been divided into three major subsegments: (i) ladder type polyphenylenes with or without heteroatoms; (ii) rigidified-aromatics as donor segments; (iii) fused polyaromatics. Planarization of organic molecules through rigidification of aromatics allows effective communication and their smaller reorganization energy is beneficial to photoinduced charge transfer. Dyes having rigidified aromatics as conjugated spacers emerged as promising candidates and a maximum efficiency of 12.5% has been achieved with DSSCs without a coadsorbate or co-sensitizer.