Sun King has been able to deliver off-grid solar electricity to 50 million people, mostly in Africa, by financing it creatively—and in the process becoming the world’s largest off-grid solar company. Founded in 2007 by T. Patrick Walsh and Anish Thakkar, Sun King charges no up-front cost for installing solar systems for families that have limited or no access to the grid and may rely on gasoline generators and kerosene lamps. The company reports that around two-thirds of new customers are getting electricity for the first time.  “Sometimes people are walking miles just to charge their phone,” says CEO Walsh. Customers pay as little as 15¢ a day for lighting, TV, fans, refrigeration, and phone charging, and can own the solar equipment in under two years. Sun King takes that recurring flow of tiny payments and securitizes it as bonds. “Climate- and impact-minded investors still need a return on capital when they provide a loan,” Thakkar says.…