The Study On “Indacenodithiopheneisatin-rhodanine” Based Non-fullerene Acceptor Photovoltaics

With the development of human society,the demand of people for fossil energy has increased day by day.Consequently,the global environmental pollution problem has increased day by day.Therefore,most countries are looking for clean and pollution-free new energy to replace fossil energy to alleviate the current global warming problem.Solar energy shows its huge development potential with its wide-ranging sources,clean energy,high energy,renewable,and easy large-scale adoption.Photovoltaic devices which can convert solar energy into electrical energy directly facilitates the use of solar energy greatly.This has brought extensive attention from the scientific fields.In addition to the commercialized silicon solar cells,many new solar cell technologies have become research hotspots,such as organic solar cells.Acceptor materials for fullerenes and their derivatives play an important role in the development of organic solar cells.Nowadays,they are still the most widely used and classic acceptor materials.However,their development have been greatly restricted due to its narrow absorption range,difficult energy level control,easy selfaggregation in the film,and poor mechanical flexibility.Therefore,the development of new acceptors that can overcome these shortcomings of fullerenes with their derivatives and maintain their excellent performance has become a research direction in the field of organic solar cells recent years.At present,non-fullerene small molecule acceptors have achieved wide attention because of their advantages of easy modification of structure,easy synthesis and purification,wide absorption range and adjustable energy level.Currently,the efficiency of bulk heterojunction organic photovoltaic devices reported in the literature has exceeded 18%,which is considered to be the most promising direction to promote the industrialization of organic photovoltaics.Therefore,designing and synthesizing non-fullerene small molecule acceptors with low-cost,high-efficiency and stability,and studying the internal mechanism of its molecular structure affecting the energy conversion efficiency of the device are several key scientific issues in the field of organic solar cells.Based on the preparation and mechanism of organic solar cell devices,this thesis explores the effects of molecular structure,energy level,and film formation process on device performance.The main contents are as follows:(1)The newly synthesized near-infrared polymer donor materials are matched with different acceptor materials to prepare near-infrared semi-transparent organic solar cell devices,and conduct performance testing and mechanism analysis on them.They are also tested by different test methods to be determined whether they can be applied to the field of organic photodetectors.These might provide certain experience for the industry.(2)By using the new A-D-A structure the " Indacenodithiophene-Isatin-Rhodanine" nonfullerene small molecule acceptor materials WH1 and WH7.Their main structural differences are the end groups.These two materials are used as electron acceptors for the preparation of organic solar cell devices.The devices are prepared by adjusting the matching degree of different donor materials and their energy levels,the ratio of D/A,and the film forming process.The methods are adjusted to optimize the photovoltaic performance parameters of the device and improve the efficiency of the organic solar cell device.Later,through the physical characterization of the device,the working mechanism of the device was discussed in depth.And the reason was analyzed for the differences in the performance of organic solar devices resulted from the differences structure of the acceptors.Therefore,the conclusions of device mechanism analysis can provide design directions for the synthesis of new organic semiconductor acceptor materials.(3)Finally,the optimization approaches for organic solar cell devices are explored through the use of enhanced optical absorption of the active layer,flexible selection of donors and acceptors combinations with complementary absorption spectra and energy level matching,D/A ratio,annealing treatment and additive process.These five methods are used to optimize device performance for different organic semiconductor material systems.We hope these explorations could provide empirical guidance for improving the efficiency of organic solar cells.