A review on 4,4′-Dimethoxydiphenylamines bearing carbazoles as hole transporting materials for highly efficient perovskite solar cell

Abstract

Perovskite solar cells have drawn global attention due to their low cost and comparable efficiency to that of conventional silicon-based solar cells. Moreover, the perovskite solar cells exhibit high efficiencies when spiro-OMeTAD has been used as the hole transport material (HTM). To attain higher PSC efficiency, spiro-OMeTAD must be in its pure form. However, the multistep synthetic protocols and purification methods required to produce high-purity spiro-OMeTAD render it economically unfeasible. Thus, there is a need to develop low-cost new organic HTMs through easy synthetic and purification methods having good solubility, good hole mobility, and thermal stability. Therefore, certain carbazole-based derivatives bearing 4,4′-dimethoxydiphenylamines (DMPA) have been investigated previously as the affordable organic HTMs alternative to the widely used spiro-OMeTAD. Thus, our current review systematically examines the most recent molecular design strategies, hole-transporting properties, power conversion efficiency, and thermal stability of organic HTMs that have been made of various carbazole derivatives bearing two, three, four, six, and eight DMPA units, as reported in the past five years.