具有高短路电流特性的D-A共聚物给体材料的理论研究

发布时间：2018-03-30 17:15

本文选题：聚合物太阳能电池　切入点：第一性原理　出处：《郑州大学》2017年硕士论文

【摘要】：高效本体异质结太阳能电池研究的重要方面之一是D-A共聚物给体材料的合理设计。本论文分别选取10种供体D单元和10种受体A单元,采用密度泛函理论,模拟了D、A单元及其相应共聚物的结构和带隙变化。在此基础上,研究了三种高短路电流给体材料P1(PDTG-PT)、P2(PNTz4T)、P3(DPPTT-T)的电子结构特性。通过分析其分子链构象、Bader电荷转移等性质,表明他们是高短路电流有机太阳能电池D-A型给体材料的理想选择。具体结果如下:(1)本文首先讨论了稠合噻吩环个数(1至6个噻吩环)对带隙值的影响。结果显示,并二噻吩的带隙值最小,随着噻吩环数目的增加,其带隙值有增大趋势。同时,这种趋势随着噻吩环个数的增多逐渐减弱。其次,苯环稠合噻吩环结构中苯环的个数对带隙值也有较大影响。本文计算的D7、D9、D10的带隙值依次为1.34eV、1.24eV、0.97eV。能够看出,随着苯环数目的增多,它们的带隙值依次减小。(2)对噻吩并噻吩和苯并二噻吩同分异构体带隙值的计算结果显示:S原子分布在分子链两侧,链间空间位阻较小,相应结构的带隙值较小;S原子分布在分子链同侧,链间空间位阻较大,相应结构的带隙值较大。本文计算的D3、D4结构带隙值依次为0.89eV、1.94eV,D7、D8结构带隙值依次为1.34eV、1.55eV。另外,桥原子替代对带隙值产生较大影响。(3)含有噻唑单元和噻二唑单元的结构具有较强的得电子能力,原因是噻唑环和噻二唑环中都含有碳氮双键,碳氮双键上的未成对电子使得这两类结构更容易得到电子。本文的计算结果显示,在同等情况下,含有噻二唑环的结构比含有噻唑环的结构具有更强的得电子能力。另外,结构中含有内酰胺基团时也具有较强的得电子能力。(4)本文对P1、P2、P3三种材料的计算表明:基于P1、P2、P3光伏器件出现高短路电流的原因一方面是因为构成聚合物本身的供体单元或受体单元的带隙值较小,另一方面是因为材料自身具有优良的晶化性能与较好的立构规整性。另外,分子链构象的结果表明:P1的二级结构为螺旋型构象,P2和P3的二级结构为直链型构象;差分电荷密度的结果表明:螺旋型构象的P1结构D、A单元之间的电荷转移较少,直链型构象的P2和P3结构的D、A单元之间电荷转移量较多。(5)模拟DPPX-T系列聚合物的带隙发现,其带隙值随着O、S、Se、Te原子半径的增加逐渐减小。另外,差分电荷密度的结果表明,单噻吩π桥在D-A共聚物内充当更多受体单元的作用,与此相反,P3结构的并噻吩π桥充当更多供体单元的作用。本研究期望为设计高短路电流D-A型给体材料提供有价值的指导。
[Abstract]:One of the important aspects in the study of high efficiency bulk heterojunction solar cells is the reasonable design of D-A copolymers. In this paper, 10 donor D units and 10 receptor A units are selected, respectively, and density functional theory (DFT) is used. The structure and band gap changes of DU A unit and its corresponding copolymers were simulated. On the basis of this, the electronic structure characteristics of three kinds of high short circuit current donor materials, P1OPDTG-PTG, P2PNTz4TP3DPPTT-T), were studied. By analyzing their molecular chain conformation, Bader charge transfer, etc. The results are as follows: (1) in this paper, the effect of the number of thiophene rings on the band gap is discussed. The band gap value of dithiophene is the smallest, and the band gap value increases with the increase of thiophene ring number, and decreases with the increase of thiophene ring number. Secondly, the band gap value increases with the increase of thiophene ring number. The band gap value is also influenced by the number of benzene rings in the dense thiophene ring structure. The calculated band gap values of D7 / D9 / D10 are 1.34 EV / 1.24 EV / 0.97 EV respectively. It can be seen that the number of benzene rings increases with the increase of the number of benzene rings. The band gap values of thiophenothiophene and benzodithiophene isomers were calculated. The results show that the atom of S is distributed on the two sides of the molecular chain, and the steric hindrance between the chains is small. The band gap value of the corresponding structure is smaller than that of the corresponding structure. The band gap value of the corresponding structure is 0.89 EV ~ 1.94 eV ~ (7) V ~ (8) and 1.34 EV ~ (1.55) EV, respectively, and the band gap value of the corresponding structure is larger in the same side of the molecular chain, and the band gap value of the corresponding structure is larger than that of the corresponding structure, and the calculated band gap value of the D _ 3 / D _ 4 structure is 0.89 EV ~ 1.94 eV ~ (7) D _ (8). The structure of thiazole unit and thiadiazole unit has strong electron ability because both thiazole ring and thiadiazole ring contain carbon and nitrogen double bonds. The unpaired electrons on the carbon-nitrogen double bond make it easier for these two kinds of structures to get electrons. The results show that, under the same conditions, the structures containing thiadiazoles have a stronger ability to obtain electrons than those containing thiazoles. In this paper, the calculation of three kinds of P1P2P2P3materials shows that the reason for the high short-circuit current of P1P2P2P3 photovoltaic device is partly because of the donor of the polymer itself. The band gap of unit or receptor unit is smaller, The results of molecular chain conformation show that the secondary structure of 1 / P1 is a helical conformation, and that of P2 and P3 is a straight chain conformation. The results of differential charge density show that there is less charge transfer between P1 units with helical conformation, and the charge transfer amount between P2 unit of linear conformation and DKA unit of P3 structure is more. 5) the band gap of DPPX-T series polymers is simulated. The band gap value decreases gradually with the increase of the atomic radius of OFS-Se Te. In addition, the differential charge density shows that the thiophene 蟺 bridge acts as more receptor units in D-A copolymers, and the difference charge density shows that the thiophene 蟺 bridge acts as more receptor units in the D-A copolymers. On the contrary, the thiophene 蟺 bridge with P3 structure acts as more donor units. This study is expected to provide valuable guidance for the design of D-A type donor materials with high short-circuit current.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM914.4

【相似文献】