Role of Ultrathin Electron Transport Layers in Performance of Dye-Sensitized and Perovskite Solar Cells

Dye-sensitized solar cells (DSCs) and perovskite solar cells (PSCs), are emerging and promising technologies amongst third-generation solar cells. Recent breakthroughs in achieving a record efficiency of 11.7% in solid DSCs at 1 sun and 32% at 1,000 lx surpass even the performance of conventional crystalline solar cells. In the context of PSCs, recent developments of new methodologies and materials are promising for achieving high efficiency as well as stability. Charge extraction layers, viz. electron (ETLs) and hole transport (HTLs) layers are important constituents of high efficient DSCs and PSCs. These layers aid in the transport of charges selectively whilst block their counterparts for an efficient solar cell. In general, 100-nm-thick TiO2 is employed to fabricate DSCs and PSCs using conventional methods, such as spin cast, spray pyrolysis and chemical bath deposition. A thinner and compact charge extraction layer (<50 nm) is desirable to reduce the series resistance and improve the transmittance and thereby the device efficiency. This chapter describes basic concepts underlying the role of ETLs in the device DSCs/PSCs. The basic principle and merits of deposition processes to prepare ultrathin films for PSCs/DSCs are discussed in detail in this chapter. Further, ultrathin ETLs prepared by different methods have been reviewed. Future directions to explore unconventional scalable and simpler technologies in the emerging field of DSCs/PSCs are discussed from the point of view of commercialization and fundamental research.