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Reviewed by Steve Fink
Research led by Siming Huang and Dr. Mojtaba Abdi Jalebi, (University College London’s Institute for Materials Discovery)
Aug 12, 2025
Associate Professor Mojtaba Abdi-Jalebi with a small prototype of photovoltaic cells optimized for indoor light. (Credit: UCL / James Tye)
LONDON — In a world racing toward 500 billion devices connected via the internet by 2030, researchers have been grappling with a massive energy challenge. How can we power an army of smart sensors, wireless gadgets, and tiny computers without constantly replacing billions of batteries?
A breakthrough published in Advanced Functional Materials might have an answer that could revolutionize green energy solutions. Scientists from University College London and several international institutions have developed indoor solar cells that can harvest energy from everyday lighting with an impressive 37.6% indoor power conversion efficiency (iPCE) under typical office lighting conditions. That figure, the highest achieved in their study, puts these cells among the top performers for their type.
The researchers focused on a special type of solar technology called wide bandgap perovskites. Unlike traditional silicon solar panels designed for outdoor use, these cells are specifically engineered to capture energy from LED lights, fluorescent bulbs, and other indoor illumination. And the potential applications are clear: powering the next generation of small, always-on devices without constant battery swaps.
The centerpiece of the research is what the team calls a “Triple Passivation Treatment” (TPT) reassembly strategy. This approach uses three chemical compounds to tackle problems that have long limited indoor solar cells, such as defects that waste energy and light-induced chemical changes that reduce performance. These compouds are rubidium chloride (RbCl), N,N-dimethyloctylammonium iodide (DMOAI), and phenethylammonium chloride (PEACl)
TPT works by altering how the solar cell material behaves at its surface. Normally, the surface has an excess of electrons (n-type behavior). The triple treatment shifts this balance to create an electron shortage (p-type behavior), making it easier for the cell to extract power from indoor light.
The scientists saw a dramatic improvement in the material’s ability to re-emit light, a sign of fewer energy-wasting defects. This measure, called photoluminescence quantum yield (PLQY), jumped fourfold, from 0.5% to 2.1%, a strong indicator of better energy conversion potential.
The team tested their solar cells under 1000 lux illumination, which is roughly the brightness of a well-lit office. In storage stability tests, the devices retained 92% of their original performance after more than four months (about 3,200 hours) at room temperature and low humidity. While this wasn’t “continuous operation” under load, it does show the material’s resilience over time.
Under tougher conditions — continuous high-temperature light soaking at 55°C for 300 hours — the cells still kept 76% of their initial efficiency. That’s particularly impressive given they were tested without protective encapsulation.
These durability improvements come from the treatment’s ability to prevent a breakdown process known as halide phase segregation, where the solar cell material chemically separates under light exposure and loses efficiency.
Indoor energy harvesting could change how connected devices operate in homes, offices, and industrial settings. Instead of replacing batteries every few months or years, smart thermostats, security sensors, environmental monitors, and countless other devices could run indefinitely on ambient indoor lighting.
The technology’s efficiency means relatively small solar panels could generate enough power for low-energy electronics. Just a few square centimeters of these advanced solar cells could potentially keep a wireless sensor or smart switch running continuously in a typical indoor environment.
“Billions of devices that require small amounts of energy rely on battery replacements – an unsustainable practice. This number will grow as the Internet of Things expands,” says senior author Dr. Mojtaba Abdi Jalebi an associate professor at the UCL Institute for Materials Discovery, in a statement. “Currently, solar cells capturing energy from indoor light are expensive and inefficient. Our specially engineered perovskite indoor solar cells can harvest much more energy than commercial cells and is more durable than other prototypes. It paves the way for electronics powered by the ambient light already present in our lives.”
Manufacturing considerations also favor this approach. Perovskite solar cells can be produced using simpler processes at relatively low temperatures, potentially making them cheaper to manufacture than traditional silicon panels.
“We are currently in discussions with industry partners to explore scale up strategies and commercial deployment,” says Abdi Jalebi.
The study represents a major step toward truly autonomous connected devices that can operate without human intervention for power management. With indoor lighting already present in nearly every built environment, these high-efficiency solar cells could turn ambient light from a simple convenience into a steady power source for the connected world.
Researchers developed wide bandgap perovskite solar cells using a chemical composition with approximately 1.75 eV bandgap. They applied a “Triple Passivation Treatment” involving three compounds: rubidium chloride deposited on the electron transport layer, N,N-dimethyloctylammonium iodide mixed into the perovskite precursor, and phenethylammonium chloride applied to the surface. The team used multiple analytical techniques including X-ray diffraction, photoluminescence spectroscopy, time-of-flight secondary ion mass spectrometry, and Kelvin probe force microscopy to characterize the materials and measure performance under both indoor LED lighting (1000 lux) and standard solar conditions.
The treated solar cells achieved 37.6% power conversion efficiency under 1000 lux indoor illumination, representing improvements in both voltage (110 mV increase) and current density (9.22 μA/cm² increase) compared to control devices. Under standard sunlight, the cells reached 20.1% efficiency with 78.5% fill factor. The treatment increased photoluminescence quantum yield fourfold (from 0.5% to 2.1%) and caused a 500 meV shift in the Fermi level, transforming surface properties from n-type to p-type. Stability testing showed 92% performance retention after 3,200 hours at room temperature and 76% retention after 300 hours under accelerated aging conditions (55°C with continuous illumination).
The study was conducted in laboratory conditions and did not test long-term performance beyond 3,200 hours under normal conditions. While the researchers demonstrated the mechanism behind the improvements, scaling the precise chemical treatment to industrial manufacturing levels remains unproven. The work focused on unencapsulated devices, so real-world deployment would require additional protective packaging that could affect performance. The study did not examine potential degradation mechanisms related to different types of indoor lighting or varying environmental conditions that devices might encounter in practical applications.
The research was supported by multiple funding sources including the Henry Royce Institute for Advanced Materials, the Engineering and Physical Sciences Research Council, University College London, University of Sydney-UCL Partnership, Cornell-UCL Global Strategic Collaboration Awards, and various international collaboration programs. The authors declared no conflicts of interest. The work involved researchers from institutions in the UK, China, and Switzerland, with equipment access provided through the Henry Royce Institute facilities.
The study “Enhancing Indoor Photovoltaic Efficiency to 37.6% Through Triple Passivation Reassembly and n-Type to p-Type Modulation in Wide Bandgap Perovskites” was published in Advanced Functional Materials on April 30, 2025. The research was conducted by Siming Huang, Shanyue Hou, Galyam Sanfo, and colleagues from University College London, Imperial College London, London South Bank University, École Polytechnique Fédérale de Lausanne, and other international institutions. The paper is available as an open access article under Creative Commons Attribution License.
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