Influence Of Composite Interfacial Layer On The Photovoltaic Performance Of Organic Solar Cells

With the continuous development of the entire human economy and society,the over-exploitation of fossil energy is gradually depleting,accompanied by environmental pollution formed in the process of production and development.Therefore,it is urgent to seek a kind of clean energy with large reserves and environmental friendliness.Solar energy has many advantages such as simple source,abundant reserves and almost no chemical pollution,and has become a research hotspot in the field of new energy in recent years.Among them,organic solar cells（OSCs）have the advantages of wide material sources,wide spectrum adaptation range,and simple preparation process.How to improve or even eliminate defects in OSCs has become one of the main research directions.In the classical structure,the electron transport layer（ETL）plays an important role in selectively transporting electrons and effectively blocking holes.A single interface layer has various defects.Therefore,by designing some composite interface layers,the interface energy barrier can be reduced,the ohmic contact between the electrode and the absorber layer can be improved,and the transport and collection of photogenerated electrons and holes can be promoted.In this paper,two kinds of composite ETL were designed by doping method and the use of interface modification materials,and the performance of OSCs based on this thin film was successfully improved.The main work is divided into two parts:（1）A composite film doped with trace iron oxide（Fe₂O₃）in zinc oxide（ZnO）was prepared.The incorporation of a trace amount of Fe₂O₃ passivates the surface defects,and the composite material can obtain higher electrical conductivity and more matched energy levels,reducing the recombination rate of photogenerated electrons and holes,thereby enhancing the electron transport efficiency of the composite ETL,and finally improving the photoelectric conversion efficiency of the device.The experimental results show that the as-prepared ZnO@Fe₂O₃ composite films have more uniform and smooth surface morphology and smaller pores on the microscopic scale compared with single ZnO films.These advantages are beneficial to reduce the interface resistance and increase the photo-generated current.The highest PCE of the devices based on a single ZnO layer prepared in the PM6:IT-4F active layer system was 11.55%,and the corresponding highest PCE of the devices based on the composite interface layer was increased to12.21%.（2）A thin layer of PC₇₁BM was introduced on the cathode interface layer ZnO to explore the effect on the photoelectric performance of OSCs.The reasons for improving device performance after modification of ZnO/PC₇₁BM composite interface layer.Due to the introduction of the PC₇₁BM layer,the interface defects are reduced,and the composite film has a stronger absorption capacity for the spectrum and a faster electron transfer rate.The composite organic solar cell device prepared based on this achieves has the highest PCE of 14.43%in the PM6:Y6 active layer system,which is higher than that of the device based on a single ZnO layer.In summary,the two composite interface layers designed in the work improve the ohmic contact between the electrode and the absorber layer,reduce the interface resistance,increase the photogenerated current density,and improve the overall performance of OSCs.It has reference value for further research in the field of interface modification.