Indoor light is an untapped source of energy for billions of small electronics. Devices like remote controls, keyboards, smoke alarms, and sensors spend their entire lifetimes in lit spaces but rely on batteries that need replacement.
As the number of connected devices grows with the rise of the Internet of Things, replacing those batteries is becoming costly, labour-intensive, and environmentally damaging.
Solar cells that can capture indoor light could solve this problem. They would use the energy already present in homes, offices, and factories to keep electronics running without the need for disposable power sources.
Yet existing indoor solar cells remain expensive and inefficient, leaving the technology far from mass adoption.
A team led by University College London (UCL) believes it has found a way forward.
Working with researchers from China and Switzerland, they have developed perovskite-based solar cells that are both more efficient and more durable than any commercially available indoor alternative.
Tackling perovskite’s biggest flaw
Perovskite is a low-cost material that has shown promise in outdoor solar panels. Unlike traditional silicon, it can be engineered to absorb specific wavelengths of light, making it suitable for dimmer environments.
But it comes with a major drawback: tiny structural defects, known as traps, that block electrons and degrade performance over time.
The UCL-led team addressed this issue with a three-part chemical approach.
They added rubidium chloride to encourage more uniform growth of perovskite crystals, which reduced the number of traps.
Two additional organic ammonium salts — N,N-dimethyloctylammonium iodide (DMOAI) and phenethylammonium chloride (PEACl) — stabilised the material’s ions, stopping them from separating into different phases that hurt efficiency.
Dr Mojtaba Abdi Jalebi, associate professor at UCL’s Institute for Materials Discovery, said billions of devices rely on battery replacements, an “unsustainable practice.”
He explained that perovskite offers another advantage as it uses materials abundant on Earth and can be manufactured through simple printing processes.
Record-breaking performance and durability
With these modifications, the team created indoor solar cells that convert 37.6% of light at 1000 lux, roughly the brightness of a well-lit office, into electricity.
That figure is about six times higher than the best commercial indoor solar cells.
Lead author and UCL PhD student Siming Huang compared the untreated material to “a cake cut into pieces” and said the team’s solution “put this cake back together again, allowing the charge to pass through it more easily.”
The cells also demonstrated impressive resilience in stress tests. Over more than 100 days, they retained 92% of their performance, compared with 76% for untreated cells.
In harsher trials involving 300 hours of intense light at 55°C, the new cells held 76% efficiency, while controls fell to 47%.
According to the researchers, the devices could power small electronics for more than five years indoors.
The team is already in discussions with industry partners to explore ways to scale up production and move towards commercial use.
The study is published in the journal Advanced Functional Materials.