Organic Solar Cells Based On A Triplet Blend

Currently, energy is the most important issue of economic development for countries in the world. Compared with inorganic solar cells, organic polymer solar cells become the focus of attention in recent years because they have advantages of thinness and lightness, wide range of sources, low cost, flexibility and large-scale. This thesis focuses on organic polymer bulk heterojunction solar cells, the main contents and conclusions are listed as following:Firstly, we prepared blends in chloroform solutions with different ratios consisting of three kinds of organic polymers, i.e. MEH-PPV, P3HT and PCBM, and made devices ITO/PEDOT:PSS/MEH-PPV:P3HT:PCBM/Al. When the ratio of mass concentration of these organic polymers are MEH-PPV:P3HT:PCBM=3:3:15 (mg/ml), the device shows best performance, i.e. PCE (Power Conversion Efficiency)= 0.39%, Jsc= 2.89 mA/cm2, Voc= 0.60V and FF= 22.3%. For the ratio of MEH-PPV:P3HT:PCBM=3:3:15 (mg/ml), an optimized interface is formed between them. In this way, the optimized interface improves the separation efficiency of excitons. Furthermore, our experimental data showed that the absorption spectrum of the blends is extended, in this way, it can absorb more incident photons.Secondly, we annealed the fabricated devices in different ways. By comparing these experimental data, the device shows best performance when the aluminum electrode was annealed at 140℃for 15 minutes after its evaporation, with PCE= 0.69%, Jsc= 3.34 mA/cm2, Voc= 0.75 V and FF= 27.5%. The reason is that the polymer interface is optimized at this temperature, and a network throughout the system is formed, which are conductive for electron and hole in their respective transfer layer, reducing the recombination, and increasing the probability of charges to reach each electrode and consequently, the short circuit current increases.Finally, we investigated the effect of LiF interlayer and Ag electrode on the performance of the device. Because LiF interlayer can modify the cathode and block the infiltrating of aluminum atoms into organic active layer, our experimental data showed 0.3-0.6 nm LiF interlayer can further improved the device performance.