Chapter 6 - Solution-processed quantum dot-sensitized solar cell based on “green” materials

Abstract

Nanosized semiconductors have been used as active sensitizers for the application of quantum dot-sensitized solar cells (QDSSCs). This type of solar cell has gained much research interest in the past few years due to the excellent optical properties of the semiconductor sensitizers and high efficiency of the solar cells. Generally, QDSSCs work on the same principle as the dye-sensitized solar cell where quantum dot (QD) sensitizers such as semicondutor CdS or CdSe are used instead of the usual inorganic dye sensitizers. To date, QDSSCs have reached a power conversion efficiency of over 13%. However, most of the reported high-efficiency QDSSCs are Cd or Pb based. To elevate the application of emerging solar cell technologies in the mainstream photovoltaic market, a low-cost, stable, and nontoxic material is crucial for the development of solar cell modules. Nontoxic QD sensitizers are usually called lead-free or cadmium-free materials. In this chapter, “green” sensitizers are reviewed and discussed. The “green” materials that have been adopted as sensitizers in QDSSCs include Sn- and Bi-based compounds. Although the performance of “green” QDSSCs such as Ag2S and Bi2S3 QDSSCs are not as high as that of CdS- or CdSe-based QDSSCs, their performance can be enhanced with the materials engineering of ternary and quaternary QD compounds and passivation layers, to name a few. The effect of these techniques will be discussed in the context of performance and fabrication techniques.