Molecular Design Of Water-soluble Photoelectric Materials And Polymer-based Hybrid Photovoltaic Devices

As the fast development of the human socity, energy issues are becoming seriousas the non-renewable fossil energy is rapidly consumed, and the enviorment issues arealso becoming serious. People have to develop renewable energy such as solar energy.Traditional Si solar cells are high cost due to the complex production processes.Therefore, people are paying more and more attention to cheap, flexibility, and easyprocessed polymer solar cells. However, this kind of photovoltaic devices need hightoxic organic solvent during the preparation process, which causes pollution to theenvironment. We hope that we can prepare the aqueous-processed solar cells withhigh performance water-soluble photoelectric materials. Through combining theadvantages of the polymer and quantum dots and constructing effective interpenetingnetwork, we can realize the clean energy with clean processes, and also the GreenChemistry concept.In chapter2, we fabricate a water-soluble PPV precursor through WesslingPolymerization process. By compositing with the PVA matrix, we can enhance the PLquantum yield. Through introducing different size and different amouts of CdTeCQDs, we can effectively control the emitting color of the hybrid materials includingthe pure white emitting color. Interestingly, we observe the energy transfer from apolymer to CQD, and we expect the energy transfer is in the form of charges transfer.Therefore, we try the planer heterjunction photovoltaic devices, we carry the surfacemodification of the CQDs, and we realize that the energy level controlled by changingthe dipole moment. The conduct band and valence band is elevated after modificating DTAB small molecule. Finally, we obtain the1.4V voltage on average, and1.46V atbest, and the devices performance is the highest voltage of the single layer devices inthe word. At the same time, we prove the charges transfer processes from thewater-soluble polymer to the CQDs.In chapter3, we prepare the aqueous-processed bulk heterjunction solar cellsdevices by employing the water-soluble PPV precursor and CdTe CQDs hybrids. Dueto the PEDOT: PSS is a water-soluble material, we fast process this material after anannealing process. After annealing, we can promote the growth of CQDs in the activelayer, and the grown CQDs can connect each other to form interpenetrating network,which ensure the efficient charge carrier transport. In addition, an annealing processcan reduce the amount of the ligands on the CQDs surface. Finally, we obtain a PCE2.14%. In order to further improve the device performance and increase the near-IRabsorption of the devices, we prepare the CdxHg1-xTe CQDs by introducing Hg intothe CdTe CQDs. As the annealing time goes, the surface ligands of CQDs areremoved and the electron mobility is also improved. We finally obtain a best PCE of1.5%after annealing one hour. The near-IR contribution from800nm to1000nm tothe photocurrent exceeds11.4%, which reaches the internationally advanced level.In chapter4, in order to further enhance the PCE of the devices, we design newlywater-soluble conjugated polymers PBTPV and PWTV by introducing thiopheneunits through Chloromethylation Reaction and Wessling Polymerization processes.The precursors of them present excellent water-soluble property, and the positivecharges on the side chains can be easily eliminated after annealing under nitrogenatmosphere. The charges carrier mobility of them are high, and they presents well inthe OFET application. The S atoms on the thiophene units can effectively coordinatewith the CQDs, this kind of interaction is in the form of secondary bond. It effectivelypromotes the charges transfer from polymers to CQDs, and it can also control thestructure and morphology of active layer. The aqueous-processed solar cells with thetwo polymers present excellent PCE results of3.3%and4.1%.