Abstract
In recent years, polymer solar cells have become an important issue, because of attention to alternative and green energy resources. For polymer solar cells, to enhance the photoelectric conversion efficiency is always the goal of all efforts. The invert polymer solar cells with a high work function metal as the anode can have a better durability and operational stability. In order to enhance the open-circuit voltage and reduce the loss of light, tandem cell gradually becomes an important issue. In the literature, usually use metal oxide and nano-particles for interlayer. First, we repeat the experiments, use MoO3, Al, and ZnO from sol-gel process in the article. But the surface of the device cracked after spin-coating of the 2nd active layer. We speculate that the heating process of ZnO-sol may cause damage to the interlayer. In the second part of this thesis, we replaced Al by Ag. Because Ag have better ductility, and it may prevent the surface from cracking. However we can see from the diagram of the optical microscope after the sintering of zinc oxide, some crack lines appears on the diagram, coating of the second active layer will rupture the status. There are no craking lines on the ZnO-sol surface without sintering, but also shows a cracking line on the surface after coating the second active layer. Therefore, we used Ag/ Al/ ZnO-sol as a component the interlayer and discuss the integrity of whether the components of the ZnO-sol in the manufacturing process. We found that no matter we use the ZnO-sol as electron transport layer or not, the surface still broken. Therefore, adjusting the ZnO-sol sintering time, we can see that the most complete film is under the process without sintering. However, the sol-gel method must have sintering for the formation of zinc oxide. Therefore we have the zinc oxide process replaced by butanol solution coating of zinc oxide nanoparticles (ZnO-np) and heated to remove residual solvent. We found that under the same condition and just change ZnO-sol into ZnO-np, the open-circuit voltage for ZnO-sol device is just 0.86 V. But for ZnO-np, the Voc is 1.15V. We speculate that some tiny cracking may cause the device partly short, and then the voltage cannot show the effect. Due to the initial experiment of the ZnO-np preparation process, there is no silver as a interconnection layer, some tiny holes appeared occasionally on the film. So we compare the silver connection layer in the device that interlayers are PEDOT/ Ag/ ZnO-np and PEDOT/ ZnO-np component efficiency and component performance. The results shows that, the device without silver layer in the interconnection layer has a higher efficiency (3.34%), when add 1nm silver as the interconnection layer the efficiency is only 2.32%, suggesting that the light penetrated through silver caused the second active layer, which resulted in the second active layer can absorb less light, resulting in lower current density of components, therefore reducing efficiency. At last, we used Ca metal to replace the zinc oxide as the electron transport layer, and hope that when the zinc oxide is replaced by Ca can reduce the damage of the coating and heating process. But the open-loop voltage only about 0.6 volts, presumably after the deposition of calcium metal difficult to scrape, and may result in the intermediate layer and the electrode contact to produce single-layer short-circuit conditions.