In the recent years, organic light emitting diodes (OLEDs) have drawn an enormous attention due to their potential application in flat panel displays, flexible electronics, and solid-state lighting (SSL). To achieve a high-efficiency OLED device considerable research has been devoted to unveiling the internalize mechanism and precisely determining electrical and optical properties. Numerous fabrication and device design approaches had been adopted to enhance the device performance, stability, lifetime, and color coordinates. The special issue willingly welcomes works devoted to the fabrication and design of high-efficiency OLED devices as well as application areas.

The main objective of this special issue of International Journal of Optics and Applications is to provide a recent applications and developments of optical imaging techniques in the field of biology and medicine. It also includes the recent developments in Biophotonics. The articles will provide a clear insight into the background of different technological as well as methodological developments towards biological and biomedical optical imaging. Laser based optical methods are highly encouraged. Each article will highlight the current challenges in the biomedical/biological imaging, future works as well as application areas.

The main objective of this special issue of International Journal of Optics and Applications is to provide a platform to disseminate the recent progress in the development of new optical materials and their applications to the broad range of readers. The articles will provide a clear insight into the background of materials development, synthesis, fabrication, physical properties and performance optimization. Each article will highlight the current challenges in materials development, future works as well as application areas.

Purpose of this special issue is to provide a common platform for the researchers and scientists across the world working in the field of photoacoustic and photothermal (PA/PT) methods to publish their work. Several decades of research and development in the field of PA/PT has made it a mature method with an established position in measurement science and material characterization. Recent advances in the field of nanotechnology have opened up a new horizon for PA/PT methods. PA/PT methods are in fact one of the few methods which finds extensive applications in all branches of science and engineering, ranging from fundamental research to sensors and imaging applications in physics, chemistry, biology, medicine, engineering and environmental sciences. Papers dealing with the advances in experimental aspects of PA/PT are preferred, but theoretical developments with experimental demonstrations will also be considered. Applications of nanotechnology in PA/PT methods are highly encouraged.

Purpose of this special issue is to collect new ideas for optical solutions to apply to photovoltaic and solar thermal energy conversion systems. Optics is the counterpart of electricity in planar (PV) or concentration photovoltaics (CPV) and of heat in solar thermodynamics (STD): optics is therefore a dominant subject in these two areas of research.

A solar system must be designed to convey the maximum amount of available radiation on the receiver, while this must be designed to absorb the maximum amount of incident radiation.

Optics plays a key role in concentrating systems (CPV and STD), because here the solar radiation has to be collected through appropriate solar tracking means and transmitted to the receiver with the maximum efficiency, ensuring also the required level of flux density.

In solar cells the radiation absorption is optimized by a suitable modeling of its surface (texturing), or by choosing appropriate dielectric window layers; this is necessary, but not sufficient, however, to reach the maximum photocurrent, because the absorbed light must be distributed in the cell bulk in such a way to minimize the recombination of the photo-generated carriers (light trapping).

The mechanism of light absorption in STD systems is different: here, the optimum coupling of the receiver with solar radiation is accomplished by a suitable modulation of the reflectance, which is minimized in the solar spectral range and maximized in the infrared, where the hot receiver emits radiation. A very important topic in current research on CPV is the development of efficient systems for the spectral splitting of solar radiation, that is expected to promote a trend of growth of conversion efficiency towards values approaching the thermodynamic limits. Other aspects of the Special Issue of particular importance are: i) optical methods and instrumentation devoted to the characterization of single components of the solar system (lenses, mirrors, etc.); ii) optical modeling and simulation of the whole system performance.

The special issue willingly welcomes also those works devoted to the study of solar radiation (availability, measurement, direct, diffuse) and of the environmental conditions (shading, cloud cover, climate) affecting the efficiency of the conversion system.