Efficiency Trends in Metal-Free Heterocyclic Sensitizers in Dye-Sensitized Solar Cell Application

The dye-sensitized solar cell (DSSC) is classified as one of the most impressive technological advancements in the solar energy conversion sector. Metal-free organic sensitizers have received more attention due to their inexpensive approaches for production, being easily obtained, outstanding ability to capture light, ease of purification, biodegradability, high structural modification flexibility, and extensive absorption range in UV–visible and near-IR regions, aside from the ruthenium(II) complex. The structural modifications of sensitizers are essential for modulating photophysical, electrochemical, and photovoltaic properties. In this review, we systematically illustrate heterocyclic moiety-based photosensitizers with distinct frameworks, namely, D-π-A, 2D-π-A, D-D-π-A, D-(-π-A)2, and A-D-π-A, based on their power conversion efficiency. This article will substantially support researchers in designing and developing more efficient sensitizers with superior power conversion efficiency.