Preparation And Characterization Of Multilayer Transparent Conductive Films

Flexible transparent organic optoelectronic devices have a good prospect of application in our life. One of the key components is excellent performance of the flexible bottom electrode(low resistance, high transmittance, flexible) and top electrode which does not destroy the organic layer as cathode and anode of the device, respectively. So far, Indium tin oxide(ITO) is the most widely used tansparent conductive film. However, ITO is the most commonly used material for transparent electrodes,4 but its brittleness and high-temperature processing limit its utility for flexible devices.5 Furthermore, the growing cost of indium has led to increasing costs of devices based on ITO electrodes. Therefore, the study of alternatives to ITO is meaningful and valuable. In recent years, the dielectric-metal-dielectric(DMD) structure transparent conductive film has aroused great concerns as electrode with room-temperature fabrication, low cost, widely optional material, good optical and electrical properties. At present, high flexiblility, good thermal stability, and adjustable work function of DMD electrodes for transparent flexible photoelectric devices are lack. Considering the nature of the dielectric materials for DMD electrode have important influence on transmittance, work function, and interface characteristics. We prepared DMD electrodes with several dielectric materials(Ni O, Sn Ox, Bi2O3) and Ag film. By optimizing the thickness of each layer, we obtain high performance anode and cathode, and use them as electrode in organic solar cells(OPVs). The key research work and results are as follows: 1. Ni O dielectric layer is first employed to construct multilayer transparentconductive films. The indium-free Ni O/Ag/Ni O(NAN) transparent electrodeexhibits a high transmittance of ~82%(590 nm), and a low sheet resistance of~7.6 Ω·sq-1. The work function of NAN is 4.7 e V, and the surface roughness is1.73 nm. The NAN electrode not only has excellent surface morphology, goodtransmittance and conductivity, but also shows good thermal, humidity, andenvironmental stabilities. The power conversion efficiencies of OPVs withNAN/PEDOT are competitive with those of ITO/PEDOT-based devices(5.20%vs. 5.76 %). 2. The NAN film is prepared on PET. The PET/NAN shows high flexibility andgood stability. The work function of NAN was raised to 5.3 e V after UV ozone(UVO) treatment. The power conversion efficiency of flexible OPVs with NANelectrode without PEDOT is 5.55%, which is competitive withPET/ITO/PEDOT-based device(4.42%). The PET/NAN-based device showsexcellent stability to bending-induced tension stress. The efficiency of deviceremain above 70% after bending 1000 times.3. The Sn Ox/Ag/Sn Ox(SAS) tansparent electrode is first prepared by e-beamevaporation with End-Hall ion assisted deposited(EHIAD). The SAStransparent electrode exhibits a high transmittance of ~88%(600 nm), and a lowsheet resistance of ~9.3 Ω·sq-1. The work function of SAS is 4.7 e V, and thesurface roughness is 1.00 nm. The power conversion efficiencies of OPVs withSAS/Zn O are competitive with those of ITO/Zn O-based devices(5.95% vs.6.39%). 4. We use the ultra-thin Bi2O3 to modify SAS for preparing Sn Ox/Ag/Sn Ox/Bi2O3(SASB) transparent conductive film. We found the thickness of 1 nm Bi2O3didn’t affect the transmittance and conductivity of SAS, but could significantlyreduce the work function of SAS electrode(from 4.7 e V to 4.2 e V). The powerconversion efficiencies of OPVs with SASB electrodes without Zn O is 6.21%,which are competitive with those of ITO/Zn O-based device(6.58%).