Today we note the contributions of three Bell Laboratories researchers who first demonstrated the ability of solar cells to power electrical devices. Experiments with photovoltaic technology had been on-going since the discoveries of A.E. Becquerel in 1839, but it wasn't until 1954 that the world was introduced to functional photovoltaic technology after a major breakthrough with silicon transistors.
Daryl Chapin was a Bell Labs engineer working on a solar energy project in the early 1950s. He was experimenting with selenium and he couldn't surpass a minimal level, 1% or so, of efficiency (internal combustion provides efficiency in the area of 20%). Calvin Fuller and Gerald Pearson were working on a separate project to develop silicon transistors when they discovered that one of their transistors, when exposed to light, created electricity. Not only had they stumbled across their own version of a solar cell: it was more effective than any known selenium cell.
Fuller and Pearson joined with Chapin to create a solar cell that surpassed the frontier of 1% energy-to-electricity efficiency. When they introduced their “solar battery” to the world in 1954, powering a toy windmill and a radio, the efficiency had reached 6%. Solar power was technologically, if not yet commercially, viable.
Incidentally, a silicon solar cell had been developed and patented by a Bell Labs researcher in the 1940s, but it had not surpassed 1% efficiency and was not commercially exploited. Even in the couple of years after 1954, solar cells weren't common because of their prohibitive cost; early implementation was limited to militaries and space agencies. But as energy efficiency has improved, so has the manufacturing efficiency and affordability.
Solar panels are used today in thousands of applications and mobile devices where power from electrical utilities, chemical batteries, or combustion is unavailable or undesirable. Efficiency levels are in the 40's. And as you've likely noticed, the desire for clean energy technology is growing. Once built, solar panels create electricity with no emissions. For kick-starting the truly fascinating solar industry, Chapin, Fuller, and Pearson are today's Heroes of Capitalism.