• Energy Research

Over the last 10 years, several organic compounds have been used to realize efficient electroluminescent devices, organic light-emitting diodes (OLED), which have now become competitive with the well-known and older inorganic semiconductor diodes, LED. Among these new luminescent compounds, the metallorganic molecule has an efficient emission band in the green region of the electromagnetic spectrum, and is easily handled. However, OLEDs realized with and other organic compounds display a lifetime defined as the time required by the emission to reduce by half its initial value, equal to about 5000 h, which is considered to be too short for practical applications. Several studies have been performed on organic compounds to understand their degradation, which has been ascribed to both intrinsic and extrinsic effects; among the latter, exposition to atmospheric agents is considered to be very important. Simple experiments have been made to verify the oxidation processes and the possibility to halt or retard them by using appropriate chemical compounds. Butylated hydroxytoluene, a molecule belonging to the big family of phenols, proved to be effective in preserving the photoluminescence of films. Our results support the idea that phenols, which are known to be strong antioxidant products, can increase the lifetime of OLEDs realized with small organic molecules and polymers. © 2002 The Electrochemical Society. All rights reserved.

Over the last 10 years, several organic compounds have been used to realize efficient electroluminescent devices, organic light-emitting diodes (OLED), which have now become competitive with the well-known and older inorganic semiconductor diodes, LED. Among these new luminescent compounds, the metallorganic molecule has an efficient emission band in the green region of the electromagnetic spectrum, and is easily handled. However, OLEDs realized with and other organic compounds display a lifetime defined as the time required by the emission to reduce by half its initial value, equal to about 5000 h, which is considered to be too short for practical applications. Several studies have been performed on organic compounds to understand their degradation, which has been ascribed to both intrinsic and extrinsic effects; among the latter, exposition to atmospheric agents is considered to be very important. Simple experiments have been made to verify the oxidation processes and the possibility to halt or retard them by using appropriate chemical compounds. Butylated hydroxytoluene, a molecule belonging to the big family of phenols, proved to be effective in preserving the photoluminescence of films. Our results support the idea that phenols, which are known to be strong antioxidant products, can increase the lifetime of OLEDs realized with small organic molecules and polymers. © 2002 The Electrochemical Society. All rights reserved.

Chemical vapor deposition (CVD) is widely utilized to synthesize graphene with controlled properties for many applications, especially when continuous films over large areas are required. Although hydrocarbons such as methane are quite efficient precursors for CVD at high temperature (similar to 1000 degrees C), finding less explosive and safer carbon sources is considered beneficial for the transition to large-scale production. In this work, we investigated the CVD growth of graphene using ethanol, which is a harmless and readily processable carbon feedstock that is expected to provide favorable kinetics. We tested a wide range of synthesis conditions (i.e., temperature, time, gas ratios), and on the basis of systematic analysis by Raman spectroscopy, we identified the optimal parameters for producing highly crystalline graphene with different numbers of layers. Our results demonstrate the importance of high temperature (1070 degrees C) for ethanol CVD and emphasize the significant effects that hydrogen and water vapor, coming from the thermal decomposition of ethanol, have on the crystal quality of the synthesized graphene.

Chemical vapor deposition (CVD) is widely utilized to synthesize graphene with controlled properties for many applications, especially when continuous films over large areas are required. Although hydrocarbons such as methane are quite efficient precursors for CVD at high temperature (similar to 1000 degrees C), finding less explosive and safer carbon sources is considered beneficial for the transition to large-scale production. In this work, we investigated the CVD growth of graphene using ethanol, which is a harmless and readily processable carbon feedstock that is expected to provide favorable kinetics. We tested a wide range of synthesis conditions (i.e., temperature, time, gas ratios), and on the basis of systematic analysis by Raman spectroscopy, we identified the optimal parameters for producing highly crystalline graphene with different numbers of layers. Our results demonstrate the importance of high temperature (1070 degrees C) for ethanol CVD and emphasize the significant effects that hydrogen and water vapor, coming from the thermal decomposition of ethanol, have on the crystal quality of the synthesized graphene.

Femtosecond coherent Raman techniques have significant diagnostic value for the sensitive and non-intrusive measurement of temperature, pressure, and composition of gas mixtures. Due to the low density of samples, however, such measurements make use of high-energy amplified laser sources, with unwieldy and costly experimental setups. In this paper, we demonstrate an experimental setup equipped with a low-energy and low-average-power femtosecond oscillator allowing measurement of the pure-rotational spectrum of nitrogen down to atmospheric pressure using impulsive stimulated Raman scattering. Using a simplified model to analyze the experimental data we were able to derive the gas temperature with reasonable accuracy.

Femtosecond coherent Raman techniques have significant diagnostic value for the sensitive and non-intrusive measurement of temperature, pressure, and composition of gas mixtures. Due to the low density of samples, however, such measurements make use of high-energy amplified laser sources, with unwieldy and costly experimental setups. In this paper, we demonstrate an experimental setup equipped with a low-energy and low-average-power femtosecond oscillator allowing measurement of the pure-rotational spectrum of nitrogen down to atmospheric pressure using impulsive stimulated Raman scattering. Using a simplified model to analyze the experimental data we were able to derive the gas temperature with reasonable accuracy.