High Efficiency Polymer Solar Cells Based On Metal Oxides As The Interface Materials

As the traditional fossil energy are faced with the crisis of energy depletion,andat the time of the application will cause a great environmental pollution.Therefore, human beings must develop and make use of some other abundantrenewable energy to meet the increasing needs. Among all kinds of renewableenergy, solar energy is the inexhaustible clean energy, so how to efficiently use ofsolar energy become the difficult scientific and technical problem which scientistsaround the world need to solve for a long time. Solar cells are the best solarcomponents, so making high efficiency, cheaper and large area of solar cells isbecoming one of the main goals of all countries clean energy technology research.Compared with traditional inorganic semiconductor solar cells, polymer solar cellshave many special advantages, such as the simple making process, ligh t quality andmaking large area of flexible devices, hence polymer solar cells have been widelyconcerned. At present, the power conversion efficiency of polymer solar cells hasmade some progress, but the stability of the device is not very good, so there is along way to go to meet the requirement of commercial application, and how toimprove the efficiency and stability of poymer solar cells is still a hot spotresearch.This paper investigated the inorganic metal oxides which are used as anelectrode interlayer to make efficient polymer solar cell, Through testing, thestability of this device is also very good. The details of experiment are shown asfollows：First, By means of magnetron sputtering, we deposited one layer of highelectron mobility and high optical transmittance of ZnO indium gallium (IGZO)film on the ITO glass as the cathode interface modification, and then we fabricatedinverted polymer solar cells (PSCs) devices which the structure isITO/IGZO/PCDTBT:PC70BM/MoO3/Al.Second, we systematically optimized the IGZO film from following aspects,including thickness, heat treatment temperature and treatment time, in order to getthe best device performance. Results show that when the thickness of IGZO film isabout20nm, the heat treatment temperature is about200℃, and the time of heattreatment is about30minutes, the device performance was best. Under AM1.5G, 100mW/cm2irradiation, the devices with IGZO interlayer exhibited PCEs of5.63%and the counterpart PCEs of3.68%. The CV testing, AFM and mobility testingindicated that when were IGZO interface layer joined, the surface morphology ofthe interface was optimized, and built-in electric field of device was enhanced, sothe carrier transfer effiency and extraction efficiency were improved.Finally, we investigated the influence of using methanol and ethanol on IGZOfilm for polymer solar cells. Measurement results show that using ethanol andmethanol solvent to treat IGZO interlayer, the performance of PSCs device is betterthan that of no solvent treatment. What’s more, ethanol treatment is better thanmethanol. The main reason of device performance improvement is that the alcoholsolvents can reduce the series resistance of the interface, so the carrier collectionefficiency can be improved.In addition, we also tested the stability of the device. The results show thatusing this method the stability of polymer solar cells can be efficiently improved.We think the main reason of the device lifetime increase is that the active layer wasspin coating between the solid IGZO film and MoO3film, so water oxygen can beefficiently isolated.