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Indika U. Perera – Papers and Thesis

Published Papers

Perera, I.U., and N. Narendran. 2018. Analysis of a remote phosphor layer heat sink to reduce phosphor operating temperature. International Journal of Heat and Mass Transfer 117: 211-222; available online 12 October 2017; doi: 10.1016/j.ijheatmasstransfer.2017.10.016.

Narendran, N., I.U. Perera, X. Mou, and D.R. Thotagamuwa. 2017. Opportunities and challenges for 3-D printing of solid-state lighting systems. Proceedings of SPIE 10378, 16th International Conference on Solid State Lighting and LED-based Illumination Systems, SPIE Optics + Photonics, San Diego, Calif., August 2017, Paper 10378-35.

Terentyeva, V., I.U. Perera, and N. Narendran. 2017. Analyzing theoretical models for predicting thermal conductivity of composite materials for LED heat sink applications. Proceedings of the IES 2017 Annual Conference, August 10-12, Portland, Oregon

Perera, I.U., and N. Narendran. 2016. Measuring the temperature of high-luminous exitance surfaces with infrared thermography in LED applications. Proceedings of SPIE 9954, Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540K (September 7, 2016); doi: 10.1117/12.2240650.

Thotagamuwa, D.R., I.U. Perera, and N. Narendran. 2016. Remote monitoring of LED lighting system performance. Proceedings of SPIE 9954, Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540I (September 7, 2016); doi: 10.1117/12.2240463.

Appaiah, P., N. Narendran, I.U. Perera, Y. Zhu, and Y. Liu. 2015. Effect of thermal stress and short-wavelength visible radiation on phosphor-embedded LED encapsulant degradation. Optical Materials 46: 6–11.
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Mou, X., N. Narendran, Y. Zhu, and I.U. Perera. 2014. Optical and thermal performance of a remote phosphor plate. Proceedings of SPIE 9190: 91900Q.

Perera, I.U., and N. Narendran. 2014. Mathematical model to analyze phosphor layer heat transfer of an LED system. Proceedings of SPIE 9190: 91900R.

Perera, I.U., and N. Narendran. 2014. Understanding heat dissipation of a remote phosphor layer in an LED system. ITHERM 2014: The 14th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems, Lake Buena Vista, FL, May 27-30, 2014, 186–192.

Perera, I.U., N. Narendran, and Y. Liu. 2013. Accurate measurement of LED lens surface temperature. Proceedings of SPIE 8835: 883506.

Perera, I.U., and N. Narendran. 2013. Thermal management of the remote phosphor layer in LED systems. Proceedings of SPIE 8835: 883504.

Doctoral Thesis Summary

Thermal Analysis of LED Phosphor Layer – December 2015

Solid-state lighting technology has progressed to a level where light-emitting diode (LED) products are either on par or better than their traditional lighting technology counterparts with respect to efficacy and lifetime. At present, the most common method to create “white” light from LEDs for illumination applications is by using the LED primary radiation and wavelength-converting materials. In this method, the re-emission from the wavelength-converting materials excited by the LED primary radiation is combined with the LED primary radiation to create the “white” light. During this conversion process, heat is generated as a result of conversion inefficiencies and other loss mechanisms in the LED and the wavelength-converting materials. This generated heat, if not properly dissipated, increases the operating temperature, thereby increasing the light output degradation of the system over both the short and long term. The heat generation of the LED and thermal management of the LED have been studied extensively. Methods to effectively dissipate heat from the LEDs and maintain lower LED operating temperature are well understood. However, investigation of factors driving heat generation, the resulting temperature distribution in the phosphor layer, and the influence of the phosphor layer temperature on LED performance and reliability have not received the same focus.

The goal of this dissertation was to understand the main factors driving heat and light generation and the transport of light and heat in the wavelength-converting layer of an LED system. Another goal was to understand the interaction between heat and light in the system and to develop and analyze a solution to reduce the wavelength-converting layer operating temperature, thereby improving light output and reliability. Even though past studies have explored generation and transfer separately for light and heat, to the best of the author’s knowledge, this is the first study that has analyzed both factors simultaneously to optimize the performance of a phosphor-converted LED system, thus contributing new knowledge to the field.

In this dissertation, a theoretical model was developed that modeled both light propagation and heat transfer in the wavelength-converting layer for identifying the factors influencing heat generation. This theoretical model included temperature-dependent phosphor efficiency and light absorption in the phosphor layer geometry. Experimental studies were used to validate the developed model. The model indicated good agreement with the experimental results. The developed theoretical model was then used to model experimental studies. These experiment results were compared with the model predicted results for total radiant power output of LED systems and phosphor layer surface temperature. These comparisons illustrated the effectiveness of a dedicated heat dissipation method in reducing the operating temperature of the wavelength-converting layer, and the contribution of different heat dissipation mechanisms were quantified using the developed numerical model. In addition to these short-term studies, an experiment was conducted to validate the effectiveness of the dedicated wavelength-converting heat sink design to improve system lifetime by reducing phosphor layer operating temperature. The proposed heat sink design decreased the operating temperature of the phosphor layer by ~10°C, improving lifetime by twofold. Finally, this dissertation investigated the potential of the developed theoretical model being used as a tool for prioritizing research tasks and as a design tool during the material selection and system configuration phases.

Rensselaer Polytechnic Institute
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