Squaraine dyes for dye-sensitized solar cells: Recent advances and future challenges

In the past few years, squaraine dyes have received increasing attention as a sensitizer for application in dye-sensitized solar cells. This class of dyes not only leaves open a good opportunity to afford conventional high performance dyes but also holds great promise for applications in transparent solar cells due to its low absorption intensity in the eye-sensitive region. This review provides a summary of the developments on squaraine dyes in the field of dye-sensitized solar cells and the opportunities used to improve their overall energy conversion efficiency. In particular, the main factors responsible for the low values of open-circuit voltage, short-circuit photocurrent and fill factor are discussed in detail. Future directions in research and development of near-infrared (NIR) organic materials and their applications are proposed from a personal perspective. Toward NIR response: Recent progress in squaraine dyes has led to a rapid increase in the energy conversion efficiency of dye-sensitized solar cells. Squaraine dyes are also a promising candidate as near-infrared (NIR) co-sensitizers in co-sensitized solar cells. In this Focus Review, we highlight some recent advances of squaraine sensitizers and their applications in dye-sensitized solar cells.