Boucar Diouf

Efficiency Control in Iridium Complex-Based Phosphorescent Light-Emitting Diodes

Key factors to control the efficiency in iridium doped red and green phosphorescent light emitting diodes (PhOLEDs) are discussed in this review: exciton confinement, charge trapping, dopant concentration and dopant molecular structure. They are not independent from each other but we attempt to present each of them in a situation where its specific effects are predominant. A good efficiency in PhOLEDs requires the triplet energy of host molecules to be sufficiently high to confine the triplet excitons within the emitting layer (EML). Furthermore, triplet excitons must be retained within the EML and should not drift into the nonradiative levels of the electron or hole transport layer (resp., ETL or HTL); this is achieved by carefully choosing the EML’s adjacent layers. We prove how reducing charge trapping results in higher efficiency in PhOLEDs. We show that there is an ideal concentration for a maximum efficiency of PhOLEDs. Finally, we present the effects of molecular structure on the efficiency of PhOLEDs using red iridium complex dopant with different modifications on the ligand to tune its highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies.

Solar Photovoltaic Electricity

The importance of green energies is continuously growing in our societies not only due to environmental concerns but also to solve the problem of access to electricity in a number of rural areas in developing countries. Photovoltaic energy is one of the most promising environment friendly sources of electricity. It does not involve any moving mechanical part and is one of the most reliable sources of renewable energies. It is a real opportunity for developed countries to lower their carbon print and for developing countries to grant access of electricity to their populations in remote rural areas.

OLED Lighting Technology

Considering the growing importance of energy savings and environment friendliness, solid-state lighting (SSL) is emerging as a highly competent and viable alternative to existing lighting technologies. White light organic light emitting devices (WOLEDs) are capturing the imagination of manufacturers, product designers, and end users owing to their potential use in SSL. Differentiating attributes of white OLEDs are brightness, high color rendering index (CRI), high contrast ratio, thin and lightweight, cost-effective and ease to deposit on plastic substrates to fabricate flexible light sources of different shapes.

Acceptability of Solar Powered LED Lighting

Rural economic development is a national priority in many developing countries. Consumption of energy is believed to be the hallmark of a modern society. Access to electricity and home lighting are essential for a higher quality of life. However, rural areas frequently lack the safe and uninterrupted electricity supply that is desired for the development of numerous economic activities.

Light Emitting Diodes

Lighting technology is continuously improving for greater comfort, higher power efficiency and due to concerns about health and environment issues. The evolution of lighting technology through conversion of electricity into light led to the revolution in Light Emitting Diodes (LEDs). LEDs are given more importance for both indoor and outdoor lighting due to their long life span compared to any other lighting technology; the very high efficiency they reach equivalent to the fluorescent lamps’ technology of today and will certainly surpass in the future; they are also very environment friendly and their price is continuously dropping making them more and more competitive. The objective of this chapter is to present the fundamentals about LEDs, the technology, operation, evolution and lighting applications. LEDs were among the first commercialized semiconductor devices; this chapter also shows why LEDs technology is the lighting technology of the future and the perfect match when considering the environment and the use of green energies. LEDs save more than 80% of energy compared to incandescent light bulbs with an efficiency comparable to fluorescent lamps of today and continuously increasing, a longer life span and a better environmental impact.

Why Clean Energy

Energy plays the most vital role in the economic growth, progress and development, poverty eradication, and security of any nation. Uninterrupted energy supply is a vital issue for a better life today. Future economic growth crucially depends on the long-term availability of energy from sources that are affordable, accessible , and environmental friendly. Acute energy scarcity is hampering industrial growth and economic progress. Strong dependence on fossil fuels for energy requirements is contributing significantly to greenhouse gases emissions. It is proposed that the introduction of renewable energy sources portfolio to the future energy mix and diversification of fuel sources will (1) enhance energy security and mitigate CO2 emission, and (2) improve the quality of life. Failing to protect the environment, would impede not only economic and industrial growths globally but also pose serious health hazards.