Fengyan Zhang

GaN light-emitting diodes with an Al-coated graphene layer as a transparent electrode

We fabricated GaN light-emitting diodes with a layer of graphene as a transparent electrode. A 3-nm-thick Al layer was deposited on the graphene layer by electron-beam evaporation. This Al layer plays an important role in protecting the graphene layer during the device fabrication process. Moreover, this Al layer can also enhance the light emission of GaN light-emitting diodes through the investigation of electroluminescence spectra. The significantly improved light emission is attributed to the current expansion, the enhanced plasmonic density of states, and the decreased non-radiative recombination rate.

Enhanced Carrier Collection in Silver Nanoparticle Embedded Zinc Oxide Nanorod Top Electrodes for Thin-Film Photovoltaic Devices

Cu(In, Ga)Se2 solar cells are the representative of high efficient thin-film solar cell with energy conversion efficiency of over 22%. However, nowadays, top electrodes of solar cells gradually become the performance limitation for optimized devices. The Al-doped ZnO thin film is widely used as a transparent top electrode in Cu(In, Ga)Se2, but there are still some techniques and electrical property issues. In this letter, we establish a ZnO/Ag/ZnO:Al multilayer top electrode, composed of ZnO nanorod arrays, Ag nanoparticles, and ZnO:Al thin films. Such multilayer top electrode was applied on Cu(In, Ga)Se2 thin-film solar cells and the devices yield a higher efficiency from 6.79% to 8.52%. Importantly, we also propose that the enhanced electronic carrier concentration in such ZnO/Ag/ZnO:Al top electrode aids the performance of solar cells. Therefore, well-designed ZnO-based top electrodes offer the opportunity to remove the bottleneck of improving the solar cell efficiency.

The applied research and solar simulation spectral design based on pulse xenon lamp with coating film

In the paper the spectrum of realistic sunlight and pulse xenon lamp were compared to each other, the result shows that the infrared part of luminescence spectrum of xenon lamp without coating film occupies the total spectrum’s 57.4%, but the infrared part of the standard solar spectrum only reaches to 28.3%. The transmittance curve of pulse xenon lamp is got by fitting. Using appropriate method and coating film parameter, the film is done to pulse xenon lamp, and the negative film coefficient transmittance is 16% is got at 935nm central wavelength. At the range of 400-760nm wavelength the average transmittance is more than 86%, and the average transmittance is more than 96% at the range of 400-760nm wavelength. A portion of infrared light can be filtered after coating film. By the spectral testing of two coating film xenon lamp, it can be found that the spectral matching rate is from 0.792 to 1.176 and it is satisfied to A grade standard request. By using A and C grade pulse xenon lamp electric performance of 40.5W thin film cell is tested and the power value by C grade simulative light source is lower than real power for 11.2W. The result indicates the spectral matching rate of solar simulator is very important for cell electric performance.