Theoretical Investigation And Molecular Design On Organic Solar Cells

In this paper, Density Functional Theory (DFT) and Time-dependent DFT (TD-DFT) were applied to investigate the photoelectric properties of a series of organic compounds. We designed some new compounds and discussed their potential application to be the donor material or acceptor material of organic solar cell, and the relationship between the newly introducted moiety and the moelecular properties after calculation of their monomer, oligomer and stacking structure.In Chapter1, we gave a brief account about the research status and the working principles of organic solar cells. Besiedes, the dornor/acceptor section and the property requirements of organic solar cells were briefly introducted. Furthermore; we gave an outlook to the development trend of organic solar cells and the importance of our work was pointed out.In Chapter2, a thorough introduction for the calculational methods applied in our paper Density Functional Theory (DFT) and Time-dependent DFT (TD-DFT) were included. In addition, we also introduced some other theoretical methods and measures, such as nature bond orbital (NBO).In Chapter3, based on the structure and properties of Poly[[l,2,5]thiadiazolo [3,4-c]pyridine-4,7-diyl(4,4-didodecyl-4H-cyclopenta[2,1-b:3,4-b’]dithiophene-2,6-diyl)](PT-CDT), cyano moiety was introduced to the pyridine and designed a new compound named PCNT-CDT via density function theory (DFT) and Time-dependent DFT (TD-DFT). The electronic, optical and photovoltaic properties and charge transport properties of monomer, dimer and trimer for the2compounds were investigated. The results reveal the newly designed PCNT-CDT equipped a lower HOMO energy level which can lead a higher open circuit voltage and smaller reorganization energies for holes and electrons compared with PT-CDT. Besides, the absorption spectrum of PCNT-CDT is broader than PT-CDT which indicates the propertiesof PCNT-CDT is better than PT-CDT. By analyzing the transport properties of2compounds, PCNT-CDT shows a suprerior behavior than PT-CDT. Hence, the newly designed polymer PCNT-CDT has the protential to become the doner material for organic solar cells.In Chapter4, density function theory (DFT) and Time-dependent DFT (TD-DFT) were adopted to analyze the properties of2,1,3-benzothiadiazole-4,7-diyl(4,9-dihydro-4,4,9,9-tetraoctylthieno[2’,3’:4,5] silolo[3,2-b]thieno[2",3":4’,5’]silolo[2’,3’:4,5]thieno[2,3-d]thiophene-2,7-diyl) D1under PBEO/6-31G(d) basis level. After an elaborate study on the electronic, optical and photovoltaic properties and transport properties, we introduced pyridine moiety and fused cyclic moiety and designed3new compounds: pyridine based dimer [1,2,5]thiadiazolo[3,4-c]pyridine-4,7-diyl(4,9-dihydro-4,4,9,9-tetraoctylthieno[2’,3’:4,5]silolo[3,2-b]thieno[2",3":4’,5’]silolo[2’,3’:4,5]thieno[2,3-d] thiophene-2,7-diyl) D2, fused cyclic based naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole-4,7-diyl(4,9-dihydro-4,4,9,9-tetraoctylthieno[2’,3’:4,5]silolo[3,2-b]thieno[2",3":4’,5’] silolo[2’,3’:4,5]thieno[2,3-d]thiophene-2,7-diyl) D3and bis[1,2,5]thiadiazolo [3,4-c:3’,4’-h][1,5]naphthyridine-4,7-diyl(4,9-dihydro-4,4,9,9-tetraoctylthieno[2’,3’:4,5] silolo[3,2-b]thieno[2",3":4’,5’] silolo[2’,3’:4,5]thieno[2,3-d]thiophene-2,7-diyl) D4. The electronic, optical and photovoltaic properties and transport properties of these four compounds were calculated and analyzed, and the impact of new introduced moiety on the properties for these compounds was studied via comparing and analyzing the calculation results.In Chapter5, we employed density function theory (DFT) and Time-dependent DFT (TD-DFT) under HSEH1PBE/6-311++G**level to investigate the properties of the wiedely used acceptor for organic solar cells,6,6-phenyl-C61-butyric acid methyl ester (PC61BM). The electronic, optical and photovoltaic properties and transport properties of PC61BM were studied. Besieds, the optical property was analyzed after combining with the typical donor material P3HT, and the distance between P3HT moiety and acceptor unit was scanned and predicted under functional HSELIPBE via Gaussian09software. Based on the structure of PC61BM, we decorate the configuration and designed a new acceptor PCPOM. The electronic, optical and photovoltaic properties and transport properties of PC61BM and PCPOM were compared and studied; the results show that the reformed acceptor PCPOM has a shallower energy level and a better absorption property than PC61BM. According to the research, the newly designed acceptor PCPOM has the protential to the acceptor material for organic solar cells.