Ni-etioporphyrin-III: Solid-state properties and photovoltaic performance
Ekaterina D. Rychikhina, Vlad V. Travkin, Andrey I. Koptyaev, K. M. Gordeev, Alexey A. Nazarov, M. R. Yakubov, N. A. Mironov, Georgy L. Pakhomov
Abstract
Nickel complexes with porphyrin-type ligands are the second most abundant in crude oil after vanadium complexes; in certain fossils, their relative concentration may be even higher. In this work, nickel(II) etioporphyrin-III, Ni-EtioP-III, a member of the etio-type family of oil porphyrins, was synthesized and investigated with a particular interest in its solid-state properties. A single-crystal X-ray analysis determined the molecular and crystal structure of Ni-EtioP-III. The electronic absorption spectra, morphology and photoelectrical parameters of vacuum-sublimed Ni-EtioP-III films were compared to those of kindred etioporphyrins compounds having a different positional isomery and central metal ions. Variations in the microscopic film morphology and crystal arrangement are poorly reflected in the absorption spectra. Archetypal thin-film photovoltaic cells with a planar donor/acceptor heterojunction where the Ni-EtioP-III donor is paired with the Cl 6 SubPc acceptor show a moderate photovoltage of 0.58 V and a short-circuit current density of 1.8 mA/cm 2 . This results in a low efficiency of no more than 1%, which is typical for planar metallo-etioporphyrins. The best photovoltaic performance with a 2.3% efficiency was measured in the cells with a non-planar vanadyl complex, VO-EtioP-III as the donor, along with a very high photosensitivity and rectification ratio of 8⋅10 5 .