Enormous effort worldwide is being put into making organic semiconductors, which could be distinguished with the most advantageous charge-transport stability and processability properties. In the synthesis of organic hole-transporting materials (HTMs) toxic inorganic compounds such as gallium, cadmium are not used. In addition, organic HTMs can be more cost-efficient in comparison with their inorganic counterparts. Therefore, it is important to continue the development of HTMs to increase the overall performance of devices of organic optoelectronics and contribute to the development of renewable power sources.
Recently, many researchers are involved in the synthesis and studies of organic HTMs for perovskite solar cells (PSC). The requirements raised for organic HTMs intended for PSC are: high hole drift mobilities, low ionization potentials, glass forming properties, morphological stability of molecular glasses, good solubility in organic solvents, good processability and reproducibility of the characteristics. HTMs in PSC is crucial for high open circuit voltage and high power conversion efficiency.
Electron rich heterocyclic systems such as carbazoles are widely utilized in the synthesis of HTMs [1]. In this work, to decrease ionization potential, electron-donating p-dimethoxydiphenylamine and p-dimethylthiodiphenylamine groups are introduced into the molecular structures of HTMs. Carbazole derivatives were chosen for the synthesis due to their excellent physical and chemical properties, such as high stability, diverse possibilities of functionalization and appropriate photovoltaic characteristics. The compounds were synthesized using different synthesis methods, primarily Ullman coupling and Buchwald-Hartwig methods.
In this presentation physical, thermal, optical and electrochemical properties of the synthesized derivates will be presented. The properties of methoxyphenyl or methylthiophenyl substituted carbazole derivatives will be compared.