Equipment like remote sensors and other electronic monitoring systems can face uncertainties ranging from lack of access to an electrical grid to environmental conditions where replacing or recharging a conventional battery is difficult.
For the U.S. Army, those variables create a fundamental challenge: how can mission-critical systems operate reliably for extended periods when solar energy or conventional batteries cannot supply sufficient power?
Nick Rolston, an assistant professor in the School of Electrical, Computer and Energy Engineering, part of the Ira A. Fulton Schools of Engineering at Arizona State University, is investigating a possible power solution at the materials science level.
“There are always going to be deployments of our armed forces in environments and under circumstances where you will not have effective access to solar energy systems to power batteries and other energy technologies,” Rolston says.
To explore new materials that address that need, Rolston has received a U.S. Army Research Office Early Career Program Award, or ECP award, for his project, “Self-Healable, Bandgap-Identical Tandems for High-Performance Radiovoltaics.”
ECP awards are prestigious honor bestowed upon outstanding scientists beginning their careers. The three-year award supports foundational research relevant to defense and funds experiments, student collaboration and new research capabilities.
“The ECP is an amazing opportunity that will enable our team to better understand the fundamental mechanisms behind designing next-generation devices for long-term operability while deepening a collaboration with the Army Research Laboratory,” Rolston says.
From light to radiation
Rolston’s latest research builds on his expertise in emerging materials for solar panel cells but now focuses on a different energy source.
Photovoltaic cells for solar energy use semiconductor materials to convert photons, or light particles, into electrical current, whereas radiovoltaic cells convert energy from ionizing radiation into electricity. In some designs, that radiation comes from the particles emitted as a particular radioactive material decays.
This underlying difference makes radiovoltaics attractive for applications that need small amounts of continuous power over long periods without regular recharging or intervention. Radiovoltaic technology with these characteristics could eventually power remote sensors, equipment or systems that must operate where access to sunlight, maintenance or replacement batteries is limited.
“Reliable continuous power sources are critical because the sun goes down at night and there are atmospheric conditions that block sunlight to power solar energy devices during the daytime,” Rolston says. “This is also important with systems that require being stationed in remote environments where they are not connected to a grid or regularly serviced.”
Rather than developing an operational power system for the U.S. Army, Rolston and his team in the Rolston Lab will study the damage effects and resilience of materials and device designs that aim to establish a scientific foundation for longer lasting radiovoltaic power sources.
“What we want to do is demonstrate how radiovoltaics and new kinds of materials can be designed and used to ensure that this goal is achievable and reliable under varying environmental conditions,” Rolston says.
The potential application of radiovoltaics also comes with a materials problem. Energetic radiation can damage a semiconductor as the device operates, introducing defects that reduce its ability to convert energy into electricity. This degradation can limit the performance and useful lifetime of a radiovoltaic device.
Rolston aims to address this challenge by expanding on his experience with self-healing semiconductor materials.
Designing materials that recover
Rolston’s research expertise extends to metal halide perovskites — lightweight semiconductor materials with unusual responses to radiation. In 2025, Rolston was selected for the U.S. Air Force Office of Scientific Research Young Investigator Program award, focusing on solar panels for satellites in space.
Unlike conventional semiconductor materials, where radiation damage can become permanent, atoms and ions within metal halide perovskites can move after irradiation and, under the right conditions, return to their original arrangement.
“There’s an element of this project that addresses interest in improving the materials themselves, because the conventional materials that we use for photovoltaics do not hold up well in very high radiation environments,” Rolston says.
That behavior gives the materials a potential self-healing capability. His ECP award research will investigate how to use this behavior in radiovoltaic devices, where radiation is not simply an environmental hazard but the energy source driving a device.
Rolston’s radiovoltaics project also points to bandgap-identical tandems, which are critical if there is a need to absorb higher-energy radiation.
A semiconductor’s bandgap determines how much energy is required to excite electrons so they can contribute to electrical current. Tandems typically layer different materials to more effectively harness various energies of sunlight for photovoltaics.
Rolston’s project proposes using the same bandgap for radiovoltaics, an approach that has not been tried before.
The goal is to investigate whether this architecture can capture more of the energy deposited by radiation while pairing that design with materials capable of recovering from radiation-induced changes.
Together, these concepts lead to the project’s central scientific hypothesis: whether a self-healing semiconductor arranged in a bandgap-identical tandem architecture can maintain or improve radiovoltaic energy conversion while limiting performance losses caused by radiation exposure.
That discovery could help researchers determine whether the technology warrants further development for defense applications requiring reliable, long-duration power — and provide a stronger foundation for engineering devices capable of operating where conventional power sources fall short.
Supporting student study
The award funding also supports an active role for engineering students and continues the core mission of Rolston’s lab to understand why emerging energy materials degrade and to find ways to design devices around those behaviors.
Rolston expects undergraduate and graduate students to participate in this research. He also anticipates opportunities for additional undergraduates through the Fulton Undergraduate Research Initiative, or FURI, providing hands-on experience with semiconductor materials, device fabrication, characterization and energy research.
“As in all of our research, student involvement is really the engine that drives these kinds of projects,” Rolston says. “In addition to funding one of our group’s doctoral students, there are several opportunities for students across engineering fields to participate. The preliminary research data that led to this grant being funded was conducted by several undergraduate students through the FURI program.”
