Susanna Thon and Sara Thoi are shedding light on the next generation of batteries—literally.

Their work developing photobatteries, batteries that can recharge themselves in sunlight, has the potential to revolutionize sustainable off-grid power. It also supports two of the primary goals of Johns Hopkins University’s Climate Action and Sustainability Plan—to lead the way in the development of innovative climate solutions through research, scholarship, and teaching and to develop the next generation of climate and sustainability leaders.

Susanna Thon (L) and Sara Thoi (R)

“You can always get a solar cell and a battery and hook them together, but the problem with doing that is often the efficiency-to-weight ratio,” says Thon, an associate professor of electrical and computer engineering. “You end up getting these big bulky systems and system complexity. We’re trying to do everything in one device.”

Thon and Thoi, associate professor of chemistry at JHU, are also teaming up to develop flexible colloidal quantum dot-based solar cells, which can be “spray painted” onto batteries to absorb surrounding visible and near-infrared light. If paired with metal organic frameworks (a class of coordination polymers with charge storage capability), both charge generation and storage could exist in one neat, tidy, and sustainable package.

“[Thoi’s] a battery expert, I’m more of a solar cell person,” Thon says. “When we get faculty candidates coming through and interviewing, this is always one of the things that I say is the best about Hopkins that I haven’t seen as much at other universities: Hopkins really encourages interdepartmental and even inter-school collaboration. And they put their money where their mouth is.”

Thon is no stranger to these types of collaborations. On top of the photobatteries, she’s been working with Yayuan Liu, assistant professor of chemical and biomolecular engineering, to create a passive system of solar cells that captures carbon dioxide from the air. She helped Hopkins and Morgan State University launch the Center for Advanced Electro-Photonics with 2D Materials, which supports her research into ultra-lightweight, flexible solar cells. And then there’s her work as associate director of the Ralph O’Connor Sustainable Energy Institute, where she oversees education and outreach efforts.

Thon also worked with associate research professor Charbel Rizk to invent a more flexible, lightweight, and effective light-emitting diode (LED) array. This invention was one of 13 JHU projects related to climate or energy innovation to receive a patent in 2024, a key step in eventually bringing the technology to market. It’s also emblematic of a burgeoning innovation ecosystem in climate science and energy systems at the university that is developing creative solutions to a range of planetary health and climate challenges.

Solar panels on the roof of the Bloomberg Student Center

“At Hopkins, I found many like-minded people,” Thon says. “The students are super motivated around topics like sustainability. This is what gives me real, actual hope for the future: The young people are passionate and totally committed to things like solving the climate crisis.”

Thon is one of countless affiliates across the university helping Hopkins pursue its ambitious sustainability goals, from students enrolled in sustainability-focused courses and degree programs to divisions improving their energy efficiency and high-performance buildings to dining services increasing plant-forward menus and compostable packaging.

In fall 2024, the Office of Climate and Sustainability announced the university’s new Climate Action and Sustainability Plan, which committed Hopkins to net-zero emissions by 2040, among other goals and targets. Today the university released a new reporting hub for data and progress updates, including a 2025 Sustainability Progress Report, highlighting the ways JHU is making progress on the Plan’s five key areas:

• Research, Teaching, and Scholarship, where Hopkins offers sustainability solutions and develops the next generation of climate leaders. Progress includes the launch of the new Johns Hopkins Institute for Planetary Health, as well as 43 sustainability-related academic programs and certificates currently offered across the university.
• Climate Action, where Hopkins works to reduce greenhouse gas emissions and prepare both its campuses and the community for future climate conditions. JHU’s greenhouse gas emissions continue to decrease annually, with emissions dropping 21% from a 2022 baseline. 77% of JHU’s purchased electricity comes from renewable and carbon-free sources.
• Built and Natural Environments, where the planning, design, and maintenance of buildings and landscapes works to enhance local biodiversity and safeguard planetary health. Progress includes the establishment of High-Performance and Healthy Buildings Requirements and 39% of JHU’s campuses being covered by tree canopy.
• Responsible Consumption, where new pathways are being built toward zero waste, more sustainable food systems, and a culture of sustainable procurement. In 2024, 37% of waste at JHU was diverted from incineration and landfill, with 20% of Hopkins Dining spending meeting industry sustainability standards.
• Transport and Mobility, where the increased use of sustainable transportation is lowering emissions and improving community health and well-being. Johns Hopkins purchased five new electric buses, and 25% of employees commute using alternative transportation methods.

One of JHU’s new electric buses, unveiled fall 2025

The new reporting hub was developed through a unique partnership between the Office of Climate and Sustainability and the Bloomberg Center for Government Excellence, a Hopkins center focused on enhancing data, research, and analytics to advance public sector innovation. Staff in both offices collaborated to envision a new way of depicting data-driven information and storytelling about JHU’s efforts to curb greenhouse gas emissions, reduce waste, enhance green space, and infuse sustainability into all aspects of the university’s programming, operations, and culture.

In addition to the five main progress areas, the report also features information about the Campus as a Living Lab program, an initiative launched by the Sustainability Leadership Council and Office of Climate and Sustainability to leverage JHU’s physical campuses as testbeds for teaching and research to inform sustainability solutions at the campus, local, and global scale. Ten teaching and research projects earned awards during the first cycle.

Students, faculty, and staff will also have the opportunity engage in upcoming programming including the annual Sustainability Symposium on April 8. This day-long event will include five concurrent informational tracks and a plenary fireside chat with interim provost Lainie Rutkow and former U.S. Sen. Ben Cardin. Information on additional Earth Month events is available on the Office of Climate and Sustainability website.

“We are extremely excited about the new reporting hub and progress report, offering deeper insights into how JHU is making progress on its sustainability efforts,” says Julian Goresko, director of sustainability. “This will increase transparency and provide data that can be used to advance a multitude of partnerships—helping leverage our campuses as living laboratories for sustainability innovation.”

This story originally appeared in the Hub. To visit the new reporting hub and read the full 2025 report, visit the Climate and Sustainability website.