Current Crowding Phenomenon: Theoretical and Direct Correlation With the Efficiency Droop of Light Emitting Diodes by a Modified ABC Model

Abstract

By incorporating current crowding effect into the conventional ABC model, we theoretically and directly uncover the black box of the relationship between the current diffusion and the internal quantum efficiency, light extraction efficiency, and external quantum efficiency droop of the light emitting diodes (LEDs). A general formula for the current diffusion length ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{s}$ </tex-math></inline-formula> ) has been derived. The design strategies on the current blocking layer and the transparent conductive layer to increase the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{s}$ </tex-math></inline-formula> have been analyzed. The impact of the vertical resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{s}$ </tex-math></inline-formula> ) on the LED wall-plug efficiency (WPE) has also been addressed. We have found there exists an optimized <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{s}$ </tex-math></inline-formula> , and the LED WPE is not always monotonically increasing as the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{s}$ </tex-math></inline-formula> decreases. Besides, our previous experiment results have been summarized to verify the theoretical analysis.