Synthesis and Spectroscopic Analysis of Trans-A2B2Metallo-Porphyrin Derivatives as Heterojunction Modulator for Organic Solar Cell

Abstract

The trans-A2B2 porphyrin and Ni-porphyrin derivatives were synthesized by Suzuki coupling of bromoporphyrin with arylborate as a key step. The band gaps of those complexes were measured from their absorption, emission and cyclic voltammetric data. All the LUMO energy level of porphyrin derivatives is lower than that of P3HT, and the HOMO energy level is evaluated higher than the HOMO of PCBM. The organic photovoltaic(OPV) is of great attractive advantages over inorganic based solar cell due to low cost and relatively simple fabrication process in solar energy industry. The low power conversion efficiency (PCE), however, below 10% is remained to be improved for commercial production. 1 The PCE of OPV system is dependent on various components of device: donor-acceptor, size or morphology of the fabricants, and the hole-electron carrier. In the P3HT-PCBM organic photovoltaic, state of the art donor-acceptor matching, the modulator such as porphyrin (PP) has been known to crucial for PCE improve. 2,3 The combination of modulators with donor- acceptor in organic solar cell altered the morphology of P3HT as well as the light harvesting efficiency at the wavelength avoiding overlap with the absorption of donor. In an effort to develop an efficient modulator for PCE improvement of P3HT-PCBM based organic solar cell, we designed PP derivatives as in Figure 1. Bulky tert-butyl group was attached to resist self-interaction of PPs and the Ar group was introduced to modulate the HOMO-LUMO energy level. Here, we report the synthesis of Ni-coordinated PP derivatives and the analysis of HOMO-LUMO energies from their absorption, emission and cyclic voltammetric data