Finally Light Bulb Company, a Boston-based company that sells a new type of light bulb based on technology invented by Nikola Tesla, announced on Wednesday it has raised a $50 million Series D round of financing, bringing its total funding to $93 million.

The Series D round was led by Brian Kelley, a partner at private equity firm Lindsay Goldberg and former president of Coca-Cola Refreshments and a former CEO of Keurig Green Mountain. As part of the round, Kelley will join the board of directors of the company.

Finally Light Bulb will use the capital to support its research and development department as well as sales and marketing efforts, including “the development of new and improved products and increased support for the expansion of retail distribution initiatives,” the company said in a press release.

As we wrote last summer, the company brought to market one of Tesla’s inventions – the copper coil – and used it to create a new kind of light bulb. The Finally Light’s signature bulb is different from the average light bulb because its core is made of copper instead of tungsten. The resulting “warm, beautiful light” is far better than the light produced by the average LED bulb, the company says. The Finally light bulbs are available in nearly 3,000 retail doors in the U.S.

“The Finally story is about solving a problem,” said Michael Simon, CEO of Finally Light Bulb, in a statement. “Innovation, perseverance and passion are all a part of the solution. In the end, we produce a product that enables people to enjoy better quality light without having to sacrifice energy efficiency and long life.”

The company, which now has 40 employees, raised its $15 million Series C round in January 2017.