Near-field photometry for organic light-emitting diodes

Rui Li; Krishnan Harikumar; Alexandar Isphording; Venkat Venkataramanan

doi:10.1117/12.2002110

4 March 2013 Near-field photometry for organic light-emitting diodes

Rui Li, Krishnan Harikumar, Alexandar Isphording, Venkat Venkataramanan

Proceedings Volume 8641, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XVII; 86410A (2013) https://doi.org/10.1117/12.2002110
Event: SPIE OPTO, 2013, San Francisco, California, United States

Abstract

Organic Light Emitting Diode (OLED) technology is rapidly maturing to be ready for next generation of light source for general lighting. The current standard test methods for solid state lighting have evolved for semiconductor sources, with point-like emission characteristics. However, OLED devices are extended surface emitters, where spatial uniformity and angular variation of brightness and colour are important. This necessitates advanced test methods to obtain meaningful data for fundamental understanding, lighting product development and deployment. In this work, a near field imaging goniophotometer was used to characterize lighting-class white OLED devices, where luminance and colour information of the pixels on the light sources were measured at a near field distance for various angles. Analysis was performed to obtain angle dependent luminous intensity, CIE chromaticity coordinates and correlated colour temperature (CCT) in the far field. Furthermore, a complete ray set with chromaticity information was generated, so that illuminance at any distance and angle from the light source can be determined. The generated ray set is needed for optical modeling and design of OLED luminaires. Our results show that luminance non-uniformity could potentially affect the luminaire aesthetics and CCT can vary with angle by more than 2000K. This leads to the same source being perceived as warm or cool depending on the viewing angle. As OLEDs are becoming commercially available, this could be a major challenge for lighting designers. Near field measurement can provide detailed specifications and quantitative comparison between OLED products for performance improvement.

Citation Download Citation

Rui Li, Krishnan Harikumar, Alexandar Isphording, and Venkat Venkataramanan "Near-field photometry for organic light-emitting diodes", Proc. SPIE 8641, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XVII, 86410A (4 March 2013); https://doi.org/10.1117/12.2002110

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KEYWORDS

Organic light emitting diodes

Near field

Deep ultraviolet

Light sources

Solid state lighting

Photometry

Light emitting diodes

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