Organic sensitizers for dye-sensitized solar cell (DSSC): Properties from computation, progress and future perspectives

The advent of the dye-sensitized solar cells (DSSCs) came at a time when the quest for alternative energy was high, replacing p-n junction photovoltaic devices. Its uniqueness arises from the fact that unlike the conventional systems where the semiconductor assumes the task of light absorption and charge transport, the two functions are separated in DSSC. Organic sensitizers have been used to harvest a large fraction of sunlight ranging from the UV region to the near infrared region of the spectrum leading to power conversion efficiencies of up to ∼ 10.65 % for metal-free organic sensitizers. Currently, experimental analysis of photo sensitizers utilized in DSSCs is often a trial and error process, often laborious and require extensive and expensive chemical synthesis. In most cases, disappointing results from late-stage of the dye synthesis indicate an urgent need to understand the properties of the dyes at a molecular level, before experiments take place. Fortunately, the use of quantum chemical calculations especially Density Functional Theory (DFT) to screen potential dyes has helped in developing efficient sensitizers and to reduce cost. In the present review article, we discuss the current state of the field, new concepts, design strategies, challenges facing the theoretical design and development of organic sensitizers for DSSCs and future perspectives.