Study On The Photoelectric Properties Of Organic Molecular Systems Containing Four Pyrrole Rings

The rapid development of the global economy is inseparable from the supply of energy,and solar energy is favored by people because of its huge energy.The development of solar cells makes it possible for people to use solar energy efficiently.Dye-sensitized solar cell（DSSC）is a new type of solar cell,which is widely concerned by researchers because of its simple manufacturing,wide source of raw materials,and no pollution.Dye sensitizers are the core components of DSSC devices,and their photoelectric performance can directly affect the photocurrent and photovoltage,thus affecting the efficiency of the solar cell.Therefore,searching for efficient and cheap sensitizers is a hot issue in the field of DSSC.Porphyrin contains four pyrrole rings,which has a high molar extinction coefficient and a characteristic that is easily modified systematically.It has special advantages in photon capture and energy conversion.To explore efficient porphyrin sensitizers,we first explained why the short-circuit current(J_SC)of double fence porphyrin is greater than that of single fence porphyrin in the experiment;Further,based on the double fence porphyrin,two new molecules were designed by adding one or two fluorine atoms to the co-receptors,respectively.The photoelectric properties of the experimental and designed molecules and the complex systems were compared.It has been found that factors such as light absorption ability,intramolecular charge transfer performance,chemical reaction parameters,and electron injection process contribute to the large J_SC in experiment for the double fence porphyrin.Compared to the original molecule,the designed molecules significantly improved various photovoltaic parameters.The strong electron-withdrawing ability of fluorine atoms can improve the photoelectric properties of double fence porphyrin,and the new molecule with two fluorine atoms introducing the co-receptor produced the highest photoelectric conversion efficiency（PCE）.Chlorophyll contains four pyrrole rings,which is one of the most abundant organic pigments on Earth.The photophysical,electrochemical,and photovoltaic properties of organic dye monomers and the chlorophyll derivative（Chl）co-sensitized systems were studied.Firstly,the geometric configuration,optical properties,and other microscopic parameters related to photoelectric properties of monomers were studied.Secondly,the heterodimers were simulated to reveal the electronic structure and intermolecular charge transfer mechanism in the co-sensitized systems.At last,an evaluation model based on D-A-π-A dyes coupled with Chl co-sensitized solar cells was established to evaluate J_SC,open-circuit voltage(V_OC),fill factor（FF）,and PCE performance.It has been found that the energy gap value,light-harvesting efficiency,electron transport ability,chemical reaction parameters,dye aggregation,and dye regeneration process of monomers affect their photoelectric properties;Compared with monomers,there were weak interactions in the co-sensitized systems,and they behaved the improved light-harvesting efficiency and excited state properties.In addition,long-distance charge transfer can occur between Chl and D-A-π-A dyes,and the co-sensitized systems achieved enhanced PCEs.This study provides a valuable reference for understanding the relationship between the structure and photoelectric properties of organic molecular systems containing four pyrrole rings,and proposes a molecular design scheme.In addition,evaluating the overall photovoltaic performance from the microscopic mechanism can provide theoretical guidance for the experimental synthesis of high-efficiency photosensitizers.