| In recent years, solar cells have been developing rapidly because ofabundant resources, environmental protection, renewable and other advantages.So, it is an important means to solve the fossil energy crisis. Compared withinorganic solar cells, organic solar cells with low cost, flexible, simplepreparation process and so on, have unlimited development potential in thefuture of social life and have the hotspot of nowadays research. Over the past tenyears, the energy conversion efficiency of organic solar cells continue toimproving, but there is still a certain distance from the requirements oflarge-scale industrialization. At the same time, the poor stability of organicmaterials is a bottleneck which restricts the application of organic solar cells.Developing new materials and optimizing the structure of the device are themain ways of improving the performance of organic solar cells. Because thecontact between the organic materials and inorganic metal electrode produceenergy level matching and interface defects, the introduction of cathode bufferlayer between the accepting material and metal electrode is a common method tooptimize the device performance. The different cathode buffer layers canoptimize the contact interface, prevent the water oxygen penetration, improvethe carrier transmission, adjust the light field distribution and other aspects ofthe function. But limitation on material property often lead to the limitedimprovement of device performance and even defect in some aspects. In order tooptimize contact interface of the device in the maximum extent, realize maximum function of the cathode buffer layer and further improve theperformance of the device, this paper introduce the compound cathode bufferlayer in the organic device and improve the performance of the device mainlyfrom the optical, electrical two aspects. The specific work is as follows:1. Utilizing the characteristics that chemical properties of Alq3is relativelystable and doping CsF in Alq3is beneficial for electron transmission, Alq3:CsF ismade as cathode buffer layer. The device with A4wt.%CsF at a thickness of5nm exhibits a power conversion efficiency(PCE) of up to0.76%, which is animprovement of49%, compared to0.55%value of the device with single Alq3cathode buffer layer. Meanwhile Alq3:CsF maintains the stability of Alq3andhalf-lifetime of the cells in air without any encapsulation is almost9.8hours,which is6times higher than that of without any buffer layer devices.2.Taking advantage of the property that BCP can block exciton and transportelectron, when another layer BCP is stacked after Alq3:CsF, the efficiency of thedevice has been further improved. The device with Alq3:CsF/BCP with a4wt.%CsF at a thickness of5nm and BCP at5nm exhibits a power conversionefficiency(PCE) of up to0.80%, which is an improvement of5.3%, compared tothe device with Alq3:CsF cathode buffer layer.3. For the purpose of adjusting the light field distribution and increasingoptical absorption of the battery active layer, the device with C60:CsF compoundcathode buffer layer with a3wt.%CsF at a thickness of20nm exhibits a powerconversion efficiency(PCE) of up to0.55%, which is an improvement of34%,compared to the device without cathode buffer layer.4. In order to further improve the efficiency, we evaporate a layer BCPbetween the C60:CsF and metal electrode. Ensuring the overall thickness20nmof cathode buffer layer, adjust the ratio of C60:CsF/BCP thickness. Theexperimental results show that the device with C60:CsF/BCP compound cathodebuffer layer with a3wt.%CsF at a thickness of8nm and BCP at12nm exhibits a power conversion efficiency(PCE) of up to0.68%, which is an improvement of28%, compared to the device with C60:CsF cathode buffer layer. |
PDF Full Text Request