Internal Quantum Efficiency
In the first part, we have introduced experimental results of the internal quantum efficiency (IQE) droop depending on temperature in both the electroluminescence and the resonant photoluminescence. The IQE droop mechanisms ever reported have been reviewe
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Internal Quantum Efficiency Jong-In Shim
Abstract In the first part, we have introduced experimental results of the internal quantum efficiency (IQE) droop depending on temperature in both the electroluminescence and the resonant photoluminescence. The IQE droop mechanisms ever reported have been reviewed. An inherent origin of the efficiency droop has been suggested as the saturation of the radiative recombination rate in the InGaN quantum well at low current and subsequent increase in the nonradiative recombination rates at high current. The degree of saturation is determined by operating temperature and effective active volume. Although the saturation of the radiative recombination rate is common origin of the IQE droop, the shapes of the IQE versus current, i.e. the IQE droop curve, vary with the dominant nonradiative recombination process. In the second part, we have reviewed the IQE measurement methods theoretically as well as experimentally. A simple IQE estimation method based on the constant ABC model in the carrier rate equation is introduced in terms of its convenience and application limitation. Other methods have been also reviewed by focusing on all-optical methods such as the temperature-dependent photoluminescence (TDPL) and the temperature-dependent time-resolved photoluminescence (TD-TRPL) methods.
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LED Efficiency
InGaN light-emitting diodes (LEDs) have been of great importance in recent years. Their applications are now in many areas such as traffic lights, mobile phones, automotives, display units, and general lighting. The application expansion capacity depends on both efficiency and reliability improvements, especially for the areas requiring high-brightness LEDs like general lighting. Usually, an LED is electrically driven by a battery producing the voltage of V and the forward current of I and the total electrical power supplied is VI. The LED J.-I. Shim (✉) Hanyang University, ERICA campus, Seoul, Korea e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2017 T.-Y. Seong et al. (eds.), III-Nitride Based Light Emitting Diodes and Applications, Topics in Applied Physics 133, DOI 10.1007/978-981-10-3755-9_7
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operation is more clearly understood when we express VI as (qV)(I/q) where q is the unit elementary charge of 1.6 × 10 − 19 ½C , I/q is the total number of electrons injected into the active layer per second, and qV is an electrical potential energy of each electron. In the ideal case, each electron energized by a battery emits one photon without any energy loss so that both quantum particles should have the same energy of qV. In a real case, however, there are many sorts of electrical and optical energy loss mechanisms during the electrical-to-optical energy conversion process. The overall efficiency of an LED is characterized by the wall-plug efficiency (ηwall-plug), which is defined by the ratio of the optical power emitted into free space from the LED to the electrical power provided to the LED [1]. Then, the wall-plug efficiency can be rewritten in de
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