With the advent of the IoT (internet of things) era, there has been discussion on how to efficiently use various information from daily life. In academic and industrial society, various smart devices such as smart watches, smart phones, and smart glasses have been developed and commercialized for narrowing the physical/psychological distance with user information. According to recent developments of smart devices, the contemporary people have desired to check their body information and treat disease by themselves. According to the needs of the time, biological researches by phototherapy/monitoring have been actively conducted. Among various light sources, microLEDs have been spotlighted due to their superior optoelectric properties and stability. In this paper, we would like to review the state-of-the research results on the next-generation biological therapy devices via microLEDs.

It was firstly found in 1st group element. Recently, it has been reported on the improvement ofefficiency of the OLEDs by introducing thin layer of some carbonate materials of alkali metal. In order toimprove the efficiency of OLEDs which is one of the next generation displays, we have studied the electricalcharacteristics of the device depending on the thickness ratio of the hole-injection layer to theelectron-injection layer. Teflon-AF was used as the hole-injection material, and alkali-metal carbonates ofLi2CO3 were used as the electron-injection materials. To obtain a proper thickness ratio, we manufactured. Fourtypes of devices with the thickness ratio of HIL to EIL were made to be 1 : 4, 2 : 3, 3 : 2, and 4 : 1. Theresults of electrical and optical properties showed that the device with the thickness ratio of 4 : 1 is the mostexcellent result. In addition, to prepare a four-layer device by inserting the α-NPD is a hole transportingmaterial was compared with three-layer element. As a result, the maximum luminance, the maximum luminousefficiency, maximum external quantum efficiency of about 124 [%], 164 [%], 106 [%] improve was confirmed.