Diego Solis-Ibarra

Diego Solis-Ibarra can think pretty quickly on his feet. He can run darn fast on them too. So fast, in fact, that this materials chemist at the National Autonomous University of Mexico (UNAM) aspired to be an Olympic triathlete. “That was my dream when I was young,” he says. It was more than a flight of fancy. Solis-Ibarra participated in Pan-American triathlons and placed near the top of his age bracket in Mexico for a few years.

“I’m competitive by nature,” he says. He’s also pragmatic. “I was decent at the sport, but I knew I wasn’t good enough to make it to the Olympics.” So he focused instead on another one of his big interests—chemistry.

Early in his undergraduate days at the university where he is now a professor, Solis-Ibarra began learning about the world’s dependence on petroleum, global warming, and other environmental consequences of burning fossil fuels. He began studying about alternative forms of energy and was inspired by the potential benefits they offered.

“It really opened my eyes,” he says. “It made me wonder how I could use chemistry to address today’s pressing energy and environmental issues.”

As a patriotic citizen of sunny Mexico, he was especially taken with the promise of solar energy, a green way to capitalize on a resource abundant in his country. He recalls chatting with college friends about the possibility of making cheap photovoltaic solar panels that could generate electricity anywhere. “The idea seemed amazing to me, and it stuck in my mind.”

Research at a glance

Solis-Ibarra’s group makes 2D layered perovskites without lead, which is toxic but commonly used in solar cells because leaded materials perform well. These lead-free materials also work well and remain stable throughout prolonged testing.

Credit: Adapted from J. Am. Chem. Soc./Yang H. Ku/C&EN

Years later, it’s still on his mind. These days, Solis-Ibarra runs a research group that focuses on solar cells containing perovskites, a family of sunlight-absorbing semiconductors. The popularity of these devices skyrocketed several years ago because their power conversion efficiency—a measure of sunlight in and electricity out—quickly reached that of crystalline silicon, the standard photovoltaic material, yet perovskites are much less expensive to make and process.

But several shortcomings have hindered manufacturing and commercialization of perovskite cells. For example, perovskites with the best power conversion efficiency values tend to decompose on exposure to moisture, heat, and intense light. They also contain lead, which is toxic.

Solis-Ibarra’s group is helping overcome those hurdles. In one study, his team came up with a way to replace lead with a combination of copper and antimony, both of which are nontoxic and abundant. Unlike single-metal substitutes, which yield poor photovoltaic performance, the mixed-metal compound stands up to heat, light, and humidity, and it conducts charge better than common perovskites.

In another study, the UNAM group gave 2D perovskites a much-needed shot in the arm. Compared with 3D perovskites, which are the common form, 2D analogs exhibit better stability when exposed to water and light, but they tend to be weak conductors. To boost conductivity, Solis-Ibarra and coworkers worked out a method for doping 2D perovskites with conjugated diynes and converting those groups to polydiace­tylenes, which remain embedded in the perovskite structure. The modification made the 2D materials better light absorbers and jacked up the conductivity by a factor of 1,000.

Hemamala Karunadasa, Solis-Ibarra’s postdoc adviser at Stanford University, describes Solis-Ibarra as “a wonderful coworker and natural teacher.” She says his work on mixed-metal compounds has motivated groups around the world to expand into that line of research, adding, “Diego is a clever scientist who has come up with some very innovative chemistry.”