Design,Synthesis And Properties Of Topological Thiophene-based Light-harvesting Materials For Organic Solar Cells

The exploitation of high efficiency,cheap,stable,solution-processed active layer material is a key to further promoting the development of organic solar cell devices and its commercialization.In this dissertaion,star-shaped structure,different strong electron-withdraw group and conjugated skeleton method were used to synthesis donor-acceptor-donor?D-A-D?and acceptor-donor-acceptor?A-D-A?type of non-fullerene small molecules active layer materials.Based on these new materials,organic solar cell devices were further prepared to study the relationship between structure and performance of organic solar cell by controllling film morphology,introducing the ternary blend structure.In particular,the main contents were divided into the following chapters:In Chapter 1,the basic principle and device structure of organic solar cells are briefly introduced.This paper elucidated the current research status of active layer materials,and mainly on the development of non-fullerene acceptor materials.Meanwhile,the advantages of developing small molecules donor or acceptor materials are described.At last part of this chapter,the research motivations and main studies of this dissertation were put forward based on these points.In Chapter 2,a series of star-shaped molecular donor materials with different cores structure were designed and synthesized.In addition,their photoelectric property was also studied.It was found that the introduction of the electron donor core structure can broaden the spectral absorption of the star-shaped molecules.The planar core star-shaped structure can enhance the stacking between the star molecules.Then,organic solar cell based on these materials with fullerenes as acceptor were fabricated and the influence between electro-optical properties of different core materials and the performance of solar cell devices was also studied.In Chapter 3,a small molecule acceptor material based on barbiturate as an end-capped was synthesized.Building A-D-A structure of small molecules no-fullerene materials can turn the energy levels,spectral absorption of materials,thus to improve the solar cell open circuit voltage,short circuit current of the devices and the power conversion efficiency of solar cell device.The fabrication of organic solar cell based on this acceptor material of the active layer does not require any pretreatment and aftertreatment,which indicated this small molecule is a promising acceptor material.In Chapter 4,follow the example of crystalline polymer P3HT,crystalline small molecules no-fullerene materials was synthezised by intercepting the segments of P3HT skeleton,which could control the accumulation and stacking of no-fullerene material molecules.The crystalline small molecules can form alloy with polymer which could improve crystallization of active layer film and carriers mobility.In addition,the modification by end-capped also turn the energy levels and absorption of no-fullerene small molecule.This advantages lead to complementary and energy levels matching between the acceptor and the donor.The absorption efficiency of the active layer and the open circuit voltage can be improved.In addition,the crystallization properties of small molecules with different solvent additives were also studied.In Chapter 5,in typical exemple such as PTB7-Th:PC₇₁BM systerm,the electron mobility of active layer is often lower than that of hole in traditional organic solar cell devices.Then,the crystalline non-fullerene small molecule acceptor was introduced to construct the ternary blend solar cells to improve the mobility of the active layer and balanced the carrier mobilities.In addition,the third component of material is used to improve the absorption of active layer and the power conversion efficiency of organic solar cells.In Chapter 6,the facile tunable chemical structures and versatile photoelectric properties of no-fullerene acceptors provide a good opportunity to design novel ternary blend systems with cascade energy levels.The star-shaped molecule material was used to provide additional transport channel to reduce the combination of carier and increase the mobility of active layer.The well designed BTTCN material was introduced as the energy level connection to PTB7-Th:PC₇₁BM host and improved the mobilities of hole and electron,thus improving the power conversion efficiency of solar cells.Introducing this kind of materials as the third component is an effective method to construct high efficient ternary solar cell.