The Structure Design And Performance Optimization Of New Type Organic Ploymer Solar Cells

Organic Solar Cells(OSCs) have attracted significant interest because their flexibility, preparation of large area, and utilizationof earth-abundant materials, especially the advantages that potentially low cost and environment friendly. However, the power conversion efficiency(PCE) of OSCs is still less satisfactory compared with inorganic solar cells, whichis the main bottleneck restricting its industrialization. According to operating principle of OSCs, lots of works focused on three aspects to improve PCE, i.e. light absorption, exciton diffusionand dissociation, as well as carrier transport and extraction. It is an important progress that bulk heterojunction(BHJ) network structure is introduced to OSCs for improving the probability of exciton dissociation by increasing the contact interface between donor and acceptor.However, the transport abilities of electron and hole could be limited in BHJ network structure to hinder the carrier transport and collection because the presence of the cut-off transport paths.If this problem is solved, the efficiency of BHJ photovoltaic devices will have a new breakthrough.In organic thin film transistors(OTFTs),the gateelectrode can form a strong electric field and waste littleconsumption.Thus, we introduce the similar structure intoPTB7:PC70BM polymer solar cells.Our proposed realize the simple and convenient modulation of electric field within the device, and improve carrier transmission, increase the rate of exciton dissociation by strong electric field. In the experiments, power conversion efficiency(PCE) of 8.1% is obtainedat 2.0 V gate bias, significantly higher than the PCE of 6.8% at the case of no gate structure. By calculating the carrier mobility and the rate of exciton dissociation efficiency in details, the role of electric field to the exciton dissociation and carrier transport was investigated, respectively. Meanwhile, the feasibility of the proposed device structure in practical application was discussed. The results suggest that such a gate structure has a great of prospects in achieving high efficiency polymer solar cells.And then, we explored the improvement of OSCs by increasing the light absorption. Three side electrode structureintroducedstrong electric field,and improved device electrical properties. If the light absorption were increased, the devices would have a higher efficiency. Rare-earth ions have fineup-conversion or down-conversion effects. We introduced rare-earth into OSCs toincreasethe light absorption.In the experiments, the performance of P3HT:PCBM polymer solar cells can be improved by incorporating NaYF4:Eu3+ions at the interface between the anode buffer layer and the active layer by optimizing the doping concentration. When the concentration is 0.0025mmol/ml, power conversion efficiency of solar cell increased from 2.43% to 2.70%, increased more than 11%. Further work should be done to optimize organic solar cells combining the three side structure and rare-earth.