One hundred ten years ago, a British inventor created the first ever light-emitting diode (LED). To mark the anniversary of this discovery, we are running a series highlighting the evolution and everyday uses of LEDs. This week, in the first of four posts, we examine the LED origin story.
At the turn of the century, new lighting technology proliferated across the United States. Innovations in durability, efficiency, and affordability made lights more accessible and appealing. Within two decades, these new bulbs became the dominant way that Americans lit their homes and businesses.
This narrative describes the flourishing of LEDs over the last few years, but it is an equally accurate description of the United States at the turn of the twentieth century. Incandescent light bulbs, first patented by Thomas Edison in 1879, evolved as Edison and competing innovators experimented with new materials and other improvements. Incandescent lights supplanted older, dirtier lights powered by gas or oil. It was amidst this environment, during the early supremacy of incandescents, that a British experimenter achieved the first breakthrough in LED technology.
A British inventor created the first light-emitting diode by accident. Henry Joseph Round worked for the Marconi Company, in the lab of long-distance radio inventor Guglielmo Marconi, where he experimented with radio technologies to improve Marconi’s equipment. In 1907, when testing the effect of running a current through a variety of substances, his discovered that when the current was applied to silicon carbine, the crystal emitted a “yellowish light.” In a letter he penned to Electrical World, he described the result as “a bright glow.” Unbeknownst to Round, he had created the first LED.
Round never followed up on the light-emitting diode; his research took him in other directions. Over a career that lasted five decades, Round submitted 117 patent applications. He contributed to British war efforts during both World War I and World War II, working with the team of researchers that discovered sonar. His initial breakthroughs in LED technology would require others to make further advancements.
Two decades later, a Soviet scientist expanded on Round’s experiments and published the first paper on light-emitting diodes. In the 1920’s, the self-taught Russian inventor Oleg Losev duplicated Round’s LED while working at the first Soviet radio in Nizhny Novgorod. There he researched semiconductors, an important material for early electronics research and the essential component in LED lights. Unfamiliar with Round’s earlier research, Losev similarly generated light by passing a current though semiconductors. Unlike Round, he continued to explore the unfamiliar phenomenon. He developed a theory about how his LED worked, considered potential practical applications, published 16 papers on his embryonic LED, and filed for the Soviet equivalent of a patent in 1927.
Losev’s tale of discovery came to a tragic conclusion in 1942. He, along with hundreds of thousands of other Soviet civilians, died of starvation during the Nazi siege of Leningrad. Despite his contributions to semiconductor research and the possibilities of LED technology, his work remained overlooked during his life and in the decades that followed. Despite Losev’s optimism about LEDs, he never found a practical use for the dull glow he generated.
The next breakthrough on LED technology took another thirty years. Before LED lights took their current form, several researchers made important discoveries of diodes that emitted light on the invisible infrared spectrum. First, RCA researcher Rubin Braunstein discovered that a simple compound diode, one composed of multiple elements, would emit light when carrying a current. While the light could be used for non-radio communication, it was not visible. Like Round and Losev, however, Braunstein never found a practical application for his discovery.
Two Texas Instruments engineers overcame this hurdle in 1961. James Biard and Gary Pittman improved Braunstein’s infrared LED and received the first US patent for an infrared LED. Using their research, Texas Instruments built the SNX-100, the first commercial available LED bulb. The SNX-100 still operated on the infrared spectrum and cost $260 dollars, but it could be used in electronics equipment. Installed into circuit boards by IBM, Biard and Pittman’s technology found the first practical application, however limited, for light-emitting diodes. This innovation opened the floodgates for LED experimentation. Soon other engineers and researchers transformed Henry Round’s “yellowish light” into the LED advances now available everywhere.
How did LEDs evolve from emitting visible light for $260 to the affordable efficiency solution of today? Stay tuned for future posts to illuminate the journey of LED history.