The Study Of SCNTs And PPDIF In Polymer Solar Cells

Solar cells have been paid more and more attention because of energy shortage in modern society. This thesis has mainly studied the performance of single walled nanotubes(SCNTs) and PPDIF in bulk heterojunction (BHJ) solar cells.It contains four aspects as follows.1. SCNTs has excellent charge carrier transporting ability, which is used as carrier transport layer in the BHJ polymer solar cells. Experimental results show that there is a strong energy transfer between SCNTs and the polymer chain at the SCNTs/P3HT:PCBM interface. Free electrons and holes are transported respectively to corresponding electrode through the SCNTs layer, avoiding gathering again in the active layer. In this way, the fill factor, short-circuit current and power conversion efficiency can be effectively increased by 13.58%,6.45% and 42.19%.2. The influence of doping SCNTs in P3HT:PCBM active layer of the device performance of BHJ solar cells was studied. In case of the doping lwt% SCNTs, the short-circuit current and fill factor increased by 15.73% and 67.57%. However,the open-circuit voltage decreases and the device stability drops, which may due to abated built-in electric field intensity by SCNTs doping between active layer/electrode interface. In case of doping concentration is higher than lwt%, SCNTs doping can damage the interpenetrating network structure, resulting in a bad device performance.3.In order to investigate the potentialities of the copolymers as electron acceptor materials for photovoltaic application, we prepare four different doping ratios of MEH-PPV and PPDIF. It can be observed that the device with a doping ratio of 1:1 shows the best performance. Then to further improve device performance, device are annealing at 150℃for 10mins,and results show that the power conversion efficiency increases to nearly 5 times of the original. Through the AFM representation can be observed that the film roughness increase obviously, which helps to form ohmic contact. It increases the active layer and electrode contact area and fill factor.4.The best doping ratio of P3HT and PPDIF is 1:1,while the best annealing temperature is 120℃.The efficiency of P3HT:PPDIF device reaches about 1.25 times of MEH-PPV:PPDIF device, and the open-circuit voltages are almost equal. But the photoelectric conversion efficiency is too low for mass production. This red crystalline material PPDIF requires improving charge carriers transporting efficiency and spectral response range, otherwise has no further research value.