Optical haze of transparent and conductive silver nanowire films

Contemporary nanostructured transparent electrodes for use in solar cells require high transmittance and high conductivity, dictating nanostructures with high aspect ratios. Optical haze is an equally important yet unstudied parameter in transparent electrodes for solar cells that is also determined by the geometry of the nanostructures that compose the electrode. In this work, the effect of the silver nanowire diameter on the optical haze values in the visible spectrum was investigated using films composed of wires with either small diameters （N60 nm） or large diameters （~150 nm）. Finite difference time domain （FDTD） simulations and experimental transmittance data confirm that smaller diameter nanowires form higher performing transparent conducting electrode （TCE） films according to the current figure of merit. While maintaining near constant transmittance and conductivity for each film, however, it was observed experimentally that films composed of silver nanowires with larger diameters have a higher haze factor than films with smaller diameters. This confirms the FDTD simulations of the haze factor for single nanowires with similarly large and small diameters. This is the first record of haze properties for Ag NWs that have been simulated or experimentally measured, and also the first evidence that the current figure of merit for TCEs is insufficient to evaluate their performance in solar cell devices.

Spatial and temporal variation of haze in China from 1961 to 2012

The purpose of this study is to analyze the climatic characteristics and long-term spatial and temporal variations of haze occurrence in China. The impact factors of haze trends are also discussed. Meteorological data from 1961 to 2012 and daily PM10 concentrations from2003 to 2012 were employed in this study. The results indicate that the annual-average hazy days at all stations have been increasing rapidly from 4 days in 1961 to 18 days in 2012. The maximum number of haze days occur in winter（41.1%） while the minimum occur in summer（10.4%）. During 1961-2012, the high occurrence areas of haze shifted from central to south and east regions of China. The Beijing-Tianjin-Hebei（Jing-Jin-Ji） region, Shanxi,Shaanxi, and Henan Province are the high occurrence areas for haze, while the Yangtze River Delta（YRD） and the Pearl River Delta（PRD） have become regions with high haze occurrences in the last 25 years. Temperature and pressure are positively correlated with the number of haze days. However, wind, relative humidity, precipitation, and sunshine duration are negatively correlated with the number of haze days. The key meteorological factors affecting the formation and dissipation of haze vary for high and low altitudes, and are closely related to anthropogenic activities. In recent years, anthropogenic activities have played a more important role in haze occurrences compared with meteorological factors.

Optical properties of conductive silver-nanowire films with different nanowire lengths

Transparent electrodes made of silver nanowires （Ag NWs） exhibit a higher flexibility than conventional indium tin oxide electrodes.For this reason,Ag NWs may find applications in future flexible electronic and optoelectronic devices.However,different optoelectronic devices have different specific requirements for Ag NWs.For example,the optical transmittance haze is an important but rarely studied aspect of Ag NW films.In this study,the optical transmittance and optical scattering of long （5-50 μm,L-NWs） and short （1-20 μm,S-NWs） Ag NW films were investigated.The L-NWs exhibited better optical transmission than the S-NWs,whereas the S-NWs exhibited better light-scattering properties than the L-NWs.Our results indicate that the L-NWs are suitable for touch-screen displays,whereas the S-NWs are better suited as transparent conductive films for solar cells.We analyzed the scattering ratio of forward-scattered light to backscattered light for both the L-NWs and S-NWs and discovered that the mesh size affected the scattering ratio.For longer wavelengths,a larger mesh yielded a higher backscattering ratio,whereas a smaller mesh yielded a lower backscattering ratio.We formulated an equation for calculating the reflection haze using the total reflection （Ag NWs/glass）,R and the reflection of glass,R0.The reflection haze of the S-NWs and L-NWs exhibited different trends in the visible-near-infrared region.An omnidirectional scattering model for the Ag NWs was used to evaluate the Ag NW scattering properties.The results of this study have great significance for the evaluation of the performance of Ag NWs in optoelectronic devices.