Research Of Solution-processed V₂O₅as Hole Transport Layer In Polymer Solar Cells

With the continuous progress of human society, energy crisis began to appear, weobviously need more and more energy. As an inexhaustible supply of clean, renewableenergy, solar energy attracts people’s attention. In recent years, as an effective way ofusing solar energy, the research of organic solar cell is becoming hot. In the course ofthe research, the appearance the bulk heterojunction solar cells greatly improved theperformance of organic photovoltaic cells, and the introducing of the electrontransport layer and the hole transport layer make the performance a greater increase.For traditional transition metal oxide materials of hole transport layer, such asWO3, NiO, V2O5, and MoO3, we usually use vacuum thermal deposition method.However, it consumes a lot of energy because of the process of vacuum. So in recentyears, the use of solution-processed transition metal oxide as hole transport layerfor organic solar cell gradually increased.As an inexpensive transition metal oxides，V2O5has a mature application in manyareas, but rarely applies on organic solar cell devices. In this paper, we firstprepared the solution-processed V2O5by a hydrothermal method in our laboratory,and then dissolved V2O5in IPA solution. The V2O5solution was spin coated on theITO substrate, we could get the complete V2O5film after annealing process.After that, we used the solution-processed V2O5as the hole transport layer oforganic polymer solar cell, the device structure is ITO/TiO2/P3HT:PCBM/V2O5/Ag.We also studied the affect of different concentrations of V2O5and various V2O5annealing temperature for the performance of the bulk heterojunction solar cell. In thispaper, the V2O5solution was spin coated on the surface of P3HT: PCBM active layer,we could get the V2O5hole transport layer after the annealing process. Thephotovoltaic device, which using such a preparation process, eliminates the process ofthermally vapor deposition hole transport layer. The process is simplified and the energy is saved, moreover, the production cost is greatly reduced. The results showthat this structure of the photovoltaic cell device, when the annealing temperature ofV2O5is80℃, the V2O5concentration is300μg/ml, the performance of the device ispreferably prepared, the short-circuit current density Jsc is about8.13mA/cm2, openvoltage Vo creaches0.56V, the fill factor FF is about0.53, the power conversionefficiency PCE is up to2.43%.Finally, we also studied the effects of different cathode substrate materials ondevice performance. We use the FTO as the substrate material of the device, thestructure is FTO/TiO2/P3HT: PCBM/V2O5/Ag. The results show that this structure ofthe photovoltaic cell device, when the annealing temperature of V2O5is80℃, theV2O5concentration is300μg/ml, the performance of the device is preferably prepared,the power conversion efficiency is up to2.38%. No matter the choice of ITOor FTO substrate as the cathode material, the optimum concentration of the V2O5solution is300μg/ml. The performance of the devices are almost the same, theperformance of the device using the ITO substrate is slightly better than the deviceusing FTO substrate.Finally, we got the conclusion: ITO substrate is the most suitable cathodesubstrate material for the polymer solar cell using V2O5as hole transport layer. Whenthe V2O5concentration is300μ g/ml, the V2O5annealing temperature is80℃, we gotthe optimum device performance, the power conversion efficiency is up to2.43%.