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The thermal and optical characteristics of phosphor converted white light-emitting diodes (LEDs) with different phosphor concentrations ranging from 4 wt % to 13 wt % are investigated. The light output of LEDs with higher phosphor concentration is found to have larger degradation in constant current compared with pulse current than that with lower phosphor concentration. In addition, the junction temperatures of phosphor converted white LEDs raise with increasing phosphor concentration, so that the decreased phosphor conversion efficiency is observed both in pulse and constant current modes. The physical mechanisms for these observations are discussed. This study elucidates the phosphor dependent optical and thermal behavior of phosphor converted white LEDs.

The interfacial structure between silver electrodes and n-type silicon emitters plays a very crucial role for the electrical and mechanical properties of silicon solar cells. Studies show that the residual glass frits layers at the Ag/Si interfaces will hugely increase the contact resistance and this subsequently leads to a decrease in the overall efficiency of the silicon solar cells. In this work, silver-coated glass frits were employed to improve the interfacial conductivity. Transfer length method (TLM) was applied to evaluate the electrical performance of samples made by different glass frits. For samples made with silver-coated glass frits, the improvement of conductivity was found to be about 15% compared to glass frits without any surface treatment.The results indicate that the silver layer on the surface of glass frits provide a conducting channel within the residual insulating layer and therefore reduce overall resistance.

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