Let There Be Light

“Let There Be Light”" a science fiction short story by Robert A. Heinlein, originally published in "Super Science Stories" magazine in May 1940 under the pseudonym Lyle Monroe.
The story concerns the invention of "light panels" - devices which turn electrical power directly into light (similar to LEDs, invented in 1962). In the course of their discovery, the inventors also discover that these panels can also be used to derive power from light. In attempting to bring their discovery to market, they encounter the active opposition of the Power Syndicate, a conglomeration of energy-producing companies dedicated to preserving their monopoly on power production