Abstract
The quest for photovoltaic technologies that harmonize high efficiency with low cost and sustainable materials has been a central driving force in the evolution of third-generation solar cells. Among these, dye-sensitized solar cells (DSSCs) have emerged as a particularly promising candidate, renowned for their potential for low-cost fabrication and remarkable performance under both ambient and indoor lighting conditions . The general principle of DSSCs operation is based on a light absorption with dye-sensitizer, excitation and charge separation, followed by injection of an excited photoelectron into the conduction band of nanocrystalline TiO2 . Therefore, the dye plays a key role in a device performance. Metal-free organic dyes have several advantages in comparison with Ru(II)-based dyes and metal-porphyrin complexes to use in DSSCs, like high molar extinction coefficients, tunable optical and electrochemical properties, low cost of their synthesis due to the use of easy-to-follow procedures, and inexpensive chemicals. In general, the most effective organic dyes contain at least a donor (D) and acceptor (A) unit linked through a π-linker. The donor part plays a pivotal role in this system. In this regard,5,11-Dihydroindolo[3,2-b]carbazole (indolo[3,2-b]carbazole, ICZ) has attracted increasing attention as a donor building block for organic optoelectronic materials and DSSC sensitizers . Structurally, ICZ can be viewed as a ladder-type π-system formed by fusion of an indole unit with a carbazole core. This fusion significantly extends the π-conjugated system relative to carbazole, increasing electron density and enhancing the electron-donating strength of the core. Herein, we report the synthesis of dyes with an A-π-D-π-A structure containing an indolo[3,2-b]carbazole fragment as the electron-donating moiety. Their physicochemical and photovoltaic properties were investigated. For the most efficient compounds, the temperature dependence of their photovoltaic performance was additionally examined.