It is found that the design efficiency of LED can be reduced

From the Nanjing University (NJU) researchers using a hybrid nanocrystals approach in InGaN / GaN (InGaN) (GaN) filled with nano crystal blue LED nanoporous structure, it can greatly improve the efficiency of white LED.

They are published in "Applied Physics Letters" (Applied Physics Letters) pointed out that the study, improve the color conversion efficiency (CCE) of the key depends on effective non radiative resonance energy transfer, rather than in the combination of blue InGaN/GaNLED and down conversion material (such as phosphorus or even semiconductor nanocrystals (NC) radiation pump etc.) often occurs when.

Non radiative resonance energy conversion (NRET) depends on the strong exciton exciton coupling. Through the carrier flow model, the researchers found that NRET can avoid loss caused by light radiation and intermediary transformation steps, and the non resonant radiation the energy conversion and resonance to has higher quantum efficiency of nano crystal.

The researchers used metal organic chemical vapor deposition, the growth of InGaN/GaN MQW epitaxial wafer in C planar patterned sapphire substrate, the manufacturing of the blue nanoporous structure of NH-LED (NH), the effective area of each LED is 300 * 300 m^2.

Using the soft UV nano imprint lithography technology, the active layer is patterned to form a hexagonal lattice with a diameter of 300nm and a distance of about 600nm. Next, the researchers applied the droplets of the CdSe/ZnS core / shell nanocrystal solution onto the element.

LED bare crystal (a) and mixed InGaN/GaN NH-LED (b) images of SEM show that the structure of the element has the shape of a nano crystal or a tin crystal. Further amplified as (c) and (D). Figure 1 (E) shows the bare hexagonal nanopore lattice, while Figure 1 (f) shows the CdSe/ZnS core / shell 5nm nanocrystals with 10nm diameter closely packed SEM.

The researchers have CdSe/ZnS core / shell filled with NC blue InGaN/GaN nano hole LED in manufacturing, they also observed and another effect analysis is to reduce the inhibition efficiency of carriers in large injection current density in the active region will have the flow, reducing the overall efficiency of the element.

By analyzing the InGaN/GaNMQW carrier concentration in the LED bare crystal and its mixed NH-LED as the control element, the researchers found that the carrier concentration in the mixed NH-LED could be reduced by NRET, and the inhibition efficiency decreased. In addition, the researchers also observed the quantum efficiency of NH-LED nanocrystals in hybrid was 44%, which was higher than that of the hybrid LED with the helplessness of the hole pattern. In this hybrid structure, they noticed that the exciton in the NH-MQW layer was more likely to pass through the NRET channel, and the decay rate of NRET was more than 3-4 times faster than that of the nanoporous MQW LED.

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