Bithiophene Derivatives As Hole-transporting Materials For Perovskite Solar Cells

In recent years, the power conversion efficiency(PCE) of perovskite solar cells has developped rapidly in the field of photovoltaic devices. So far, the latest efficiency reported in literatures has exceeded 20%, becoming the research hot spot. However, the performance in stability of the device shoule be improved to achieve the commercial application. As we know, hole-transporting materials and additives are all factors that affect the efficiency and stability in perovskite solar cells. In order to reduce production costs and improve the stability of the device, promote the large-scale application of perovskite solar cells, the following two aspects are mainly studied in this thesis:First of all, in the absence of additives, a class materials of quasi-three dimensional structure which α,α’-bithiophene as the nuclear were used into the perovskite solar cells as hole-transporting materials, to avoid using the material of Spiro-OMeTAD which the synthesis process is complex and expensive. The experimental evidence suggests that the device with DEPT-SC as hole-transporting layer showed the best performance of 9.73%. Carrier mobility and static fluorescence spectrum confirmed the material of DEPT-SC has a better hole-transporting abilities.What’s more, p-type organic additive of F4 TCNQ was introduced into the material of DEPT-SC to further improve the efficiency of the device. Compared with the pure device performance, the efficiency of the device doped with 1wt% F4 TCNQ was large improved. The best photovoltaic performance is as large as 11.52%. Compared with the pure device, Mainly displays in the dark current decreased, the open circuit voltage was improved about 60 mV and the fill factor was optimized to 0.724.Last, in the same environment, we test the performance of the device, the decline curve shows that the stability of the device are better when using the bithiophene materials. Moreover, we can see that the additive of F4 TCNQ have little impact on the stability of the device. The water contact angle is about the same after doping the additive F4 TCNQ into DEPT-SC. As we can see, solid F4 TCNQ is a p-type additive with excellent properties.