Synthesis and investigation of charge transport properties in adducts of hole transporting carbazole derivatives and push-pull azobenzenes

Abstract

In order to investigate the viability of a material design for bulk heterojunction (BHJ) organic solar cells, where hole transporting group is bound to the donor moiety, we report the synthesis and charge transport characteristics of 3-(diphenylamino)carbazolyl-functionalized derivatives of 2-(4-((4-(dimethylamino)phenyl)diazenyl)benzylidene)-1H-indene-1,3-dione (DMAAzi) chromophore. Three different bounding configurations were examined in these adducts. Additionally, a trityl-functionalized derivative of DMAAzi was prepared and used for comparison purposes. All of the synthesized materials form thin amorphous films from volatile organic solvents and exhibit glass transition temperatures in the range from 89 °C to 124 °C. The molecular ionization energy and electron affinity energy levels in thin films were measured. Photo-induced time of flight (ToF) method was used in to determine charge carrier drift mobilities. It was found out that the formation of deep charge trap states with local energies at approximately 0.60–0.78 eV takes place and has a considerable negative effect on the hole drift mobility of the investigated compounds.