In 1968, breakthroughs were made in LED research and development. The use of nitrogen doping enabled the efficiency of GaAs devices to reach 1 lm / W and emit red, orange and yellow light. By 1971, the industry introduced the GaP green die LED with the same efficiency. Since 1972 a small amount of LED display for clocks and calculators. The world's first LED-based watch was originally sold in expensive jewelers for as much as $ 2,100. Almost at the same time, HP and Texas Instruments also introduced a calculator with a 7-segment red LED display. By the 1970s, the price of LED plummeted due to the large number of applications of LED devices in home and office equipment. In fact, LED is the flagship of the era of digital and text display technology. However, in many commercial devices, LED displays are also increasingly fierce competition from other display technologies, such as liquid crystal, plasma and vacuum fluorescent tube displays.
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