Novel application of Yttria Stabilized Zirconia as a substrate for thin film CIGS solar cells
Yttria Stabilized Zirconia [YSZ] has a number of qualities that make it attractive as a substrate for fabrication of thin film copper indium gallium diselenide [CIGS] solar cells: these include flexibility, a smooth surface, lack of impurities such as iron and the ability to scale to a roll-to-roll format. As an insulator, YSZ is compatible with monolithic processing and its high temperature capabilities enable high efficiency deposition temperature. Small area [0.41 cm2] CIGS solar cells were fabricated on a YSZ substrate yielding a 17.3% efficient device.
Breaking and Connecting: Highly Hazy and Transparent Regenerated Networked-Nanofibrous Cellulose Films via Combination of Hydrolysis and Crosslinking
High optical transparency combined with high optical haze are essential requirements for optoelectronic substrates. Light scattering caused by haze is responsible for increasing light harvesting in photon-absorbing active materials, hence increasing efficiencies. A trade-off between transparency and haze is common in solar substrates with high transparency (~90%) and low optical haze (~20%), or vice versa. In this study, we report a novel, highly transparent film fabricated from regenerated cellulose after controlled acid-hydrolysis of microcrystalline cellulose (MCC). The developed networked-nanofibrous cellulose was chemically crosslinked with glutaraldehyde (GA) and vacuum-cured to facilitate the fabrication of mechanically stable films. The effects of crosslinker concentration, crosslinking time, and curing temperature were investigated. Optimum conditions for fabrication unveils high optical transparency (~94%) and high haze (~60%), using 25% GA for 24 hr with a curing temperature of 25 °C; therefore, conveying an optimal substrate for optoelectronics applications. The high haze arises primarily from the crystalline, networked crystals of cellulose II structure formed within the regenerated cellulose upon hydrolysis. Moreover, the developed crosslinked film presents high thermal stability, water resistance, and good mechanical resilience. This high-performance crosslinked cellulose film can be considered a potential material for new environmentally-friendly optical substrates.
What Happened to Suicide Bombings in Israel? Insights from a Terror Stock Model
An analysis of three years of suicide bombing data in Israel reveals an increase in such attacks through March 2002 followed by a steep decline through the end of 2003. The authors propose a terror-stock model that treats the suicide bombing attack rate as a function of the number of terrorists available to plan and execute suicide bombings. The intent of Israeli tactics such as targeted killings and preemptive arrests is to reduce the capacity of terror organizations to commit attacks. When fit to the data, this model suggests that the targeted killing of terror suspects sparks estimated recruitment to the terror stock that increases rather than decreases the rate of suicide bombings. Surprisingly, only the deaths of suspected terrorists, and not Palestinian civilians, are associated with such estimated recruitment. Although Israeli actions have reduced the rate of suicide bombings over time, it is preventive arrests rather than targeted killings that seem more responsible for this outcome.