Synthesis And Properties Of Porphyrin Based Organic Small Molecule Photovoltaic Materials

Small molecular organic photovoltaic materials have attracted a large number of researchers,and have made remarkable achievements,because of its easy synthesis and modification in molecular structures,wide source of raw materials,the device has simple manufacture technology,low cost of device fabrications,large-scale production and other advantages.Porphyrin have been a promising unit to construct donor materials for having large conjugation system with 18 electrons,good planarity,fine stability and high hole mobility.In this paper,we designed and synthesized six porphyrin based small molecule donor materials by choosing porphyrin as electron donor unit and diketopyrrolopyrrole as electron acceptor unit.Based on density functional theory calculations,we acquired the optimized molecular structure and electronic cloud distributions.Meanwhile,the optical and electrochemical properties were measured by UV-Vis absorption spectra and cyclic voltammetry.Finally,the synthesized donor materials and the acceptor material PC₆₁BM were blended to fabricate BHJ organic solar cell devices,and the photovoltaic performance of the devices were fully investigated.This paper shows that the introduction of different electronegativity groups on the symmetric porphyrin small molecules not only increases the molecular weight of the molecules,but also reduces the solubility of the materials,so it is not suitable as donor materials.The design of asymmetric porphyrin materials has greatly reduced the relative molecular mass and achieved good solubility.Therefore,it is suitable for organic small molecule solar cells as donor materials.Furthermore the introduction of different electronegativity groups the end-capping unit has a significant effect on the optical absorption and energy level,and thus affects the photovoltaic performance.The devices based on ZnPTDPPCN showed 4.26%high efficiency without adding any additives,and the filling factor reached 0.43.The devices based on ZnPTDPPO obtained 4.24%PCE without any additive,and the short circuit current density reached 15.54 mA·cm^-2 The design idea of molecular structure used in this paper provides important reference value for the molecular design of porphyrin organic small molecule photovoltaic materials.