Sensitized photocurrents in molecular dispersions of 5′-[4-[bis(4-ethylphenyl)amino]phenyl]-N,N,N′,N′-tetrakis(4-ethylphenyl)-[1,1′:3′,1″-terphenyl]-4,4″-diamine

The photosensitized injection of holes from an adsorbed rhodamine dye into a polycarbonate film, molecularly doped with 5′-[4-[bis(4-ethylphenyl)amino]phenyl]-N,N,N′,N′-tetrakis(4-ethylphenyl)-[1,1′:3′,1″-terphenyl]-4,4″-diamine, has been investigated using photoconductivity. The small quantum yields for sensitized hole injection as well as their dependence upon the applied field are attributed to the competition between the escape of the injected holes and recombination with the reduced molecules at the surface. While in a first approach the experimental results can be explained by extending the Willig–Gerischer model, developed for organic single crystals, to doped polymers, a more accurate description of this system also requires the consideration of the diagonal and non-diagonal disorder of the hole transport material.