ABSTRACT
Natural light from the sun is a primary sustainable element for life on Earth. Sunlight is a diffused and continuous visible radiation with varying chromaticity from dawn to dusk, also changing with the weather and the region. This radiation, which is of the highest quality, reproduces the true and natural colors of objects but, unfortunately, cannot be retained for illumination after dusk. Five thousand years ago, the ancient Egyptians introduced candles to provide lighting at night. These hydrocarbon-burning lighting sources, while emitting a high-quality radiation that is almost free of blue hazard, are unfortunately energy inefficienct, a major obstacle. Lighting sources powered by electricity emerged 200 years ago and developed continuously in terms of their energy efficiency. However, most of the emission spectra of these lighting sources are not diffused and soft, and their chromaticity is not perfectly similar to that of blackbody radiation. Modern lighting measures, such as compact fluorescent tubes and light-emitting diodes, have a large share of the illumination market, but barely satisfy our desire for the natural lighting given by the sun. By using organic light-emitting diode (OLED) technology, chromaticity with a varying color temperature similar to that of sunlight can be obtained. In this book, we comprehensively discuss the design and development of natural light-style OLEDs such as a sunlight-style OLED, low color-temperature OLED, candlelight-style OLED, sunset-style OLED, and pseudo-style 482natural light OLED. We also discuss the status of and issues with current light-quality matrices and introduce a new metric with which to measure the quality of light, such as its resemblance to the spectra of sunlight and natural light. The discussion we present is intended to provide a path leading to healthy illumination and to open up a new era in solid-state lighting in order to trigger a “Lighting Renaissance.”
