o,p-Dimethoxybiphenyl Arylamine Substituted Porphyrins as Hole Transport Materials: Electrochemical, Photophysical and Carrier Mobility Characterization.

Carrier mobility in organic thin films is a key parameter for devices that use molecules as selective contacts such as organic and perovskite solar cells. Herein we describe the synthesis of a free base porphyrin symmetrically substituted with four meso-4-aminophenyl-N,N-bis(2′,4′-dimethoxy[1,1′-biphenyl]-4-yl) units and its metalloporphyrin. The electrochemical and photophysical properties for both porphyrins have been measured. The results show that the HOMO and LUMO energy levels are appropriated for its use as hole transport materials (HTM) in solar cells. Moreover, the measurements of the carrier mobility by using the Space Charge Limited Current (SCLC) method in organic thin films leads to a hole mobility value of 2.4±0.5·10-5 cm2/Vs and 8.0±0.5·10-6 for the zinc porphyrin and the free base, respectively. Upon addition of chemical dopants the mobility values increased to 8.8±0.5·10-4 cm2/Vs, for the zinc porphyrin, and 5.2 ± 0.5·10-4 cm2/Vs for the free base porphyrin. Those values are close to the reference molecule used, the spiro-OMeTAD, which has a mobility value of 2.5±0.5·10-4 cm2/Vs measured using identical conditions.