Interfacial Modification And Performance Optimization Of Polymer Solar Cells

Polymer solar cells（PSCs）have been attracting the attention to researchers due to their light weight,low cost,preparation of easy,and environmental friendliness.The high power conversion efficiency（PCE）and the stability of the devices will be essential to the commercialization and industrialization of PSCs.In addition to the development of new active layer materials and the optimization of device fabrication methods,the improvement of effective device structure and the interface modulation between electrode and active layer have also been the focus of research.In this thesis,for interface problems of PSCs,three different interfacial modification materials have been chosen to study the effects of interfacial engineering on photovoltaic devices.The study is summarized as follows:Firstly,V₂O₅ nanoparticles have been doped into the classical anode interface transport layer material PEDOT:PSS.In the preparation of PSCs,PCE was significantly increased to9.44%,and filling factor（FF）was significantly increased.Because with the addition of V₂O₅nanoparticles,the pores of PEDOT:PSS have been filled,and more PEDOT chains have been exposed on the surface,which have made PEDOT:PSS with poor electrical conductivity get a good enhancement.Grazing incident wide-angle X-ray scattering（GIWAXS）atomic force microscopy（AFM）and water contact Angle（WCA）results showed that the hole transport layer of organic-inorganic heterocomposite can improved the morphology of the active layer the spin coating of the active layer on the composite anode interface transport layer enhanced the ordered molecular accumulation and improved the charge transport which have good ohmic contact and result in a more favorable transport holes.Secondly,traditional photovoltaic devices were prepared by using iminodisuccinate tetrasodium（IDS）organic molecule with simple structure as electron transfer layer（ETL）of PSC_S cathode.The results showed that the PCE of the devices reached 9.33%with IDS as ETL and PTB7-Th:PC₇₁BM as the active layer.Through AFM,exciton dissociation,WCA,and impedance spectroscopy（IS）,we found that the use of IDS as ETL not only improved the good contact between the electrode and the active layer and increased the carrier mobility but also beneficial to exciton dissociation and transport,and more effective in decreasing exciton complexation.Finally,L-cysteine,a natural and biologically existing small molecular material,was selected as the ETL material for PSCs.The performance of the photovoltaic devices was substantially improved,which mainly showed a PCE to 9.44%.The insertion of L-cystine can significantly increased the carrier mobility of photovoltaic devices and made the migration within the devices more balanced.The excellent film-forming performance of L-cystine improved the ohmic contact between the cathode and the active layer,promoted charge transfer,thus improving the photovoltaic performance of the device.It provided a reference for the adoption of high quality,low cost and green ETL in organic photovoltaics,which will also facilitated the commercialization of organic photovoltaics.