Modified perovskite solar cells harvest energy from indoor fluorescent lighting

When you think of solar panels, you usually picture giant cells mounted to face the sun. But what if “solar” cells could be charged using fluorescent lights?

Perovskite solar cells (PeSCs) have emerged as a lower-cost, higher-efficiency alternative to traditional silicon solar cells due to their material structure and physical flexibility. Their large power conversion efficiency rate (PCE), which is the amount of energy created from the amount of energy hitting the cell, makes PeSCs well suited to converting lower light sources into energy.

In APL Energy, researchers from National Yang Ming Chiao Tung University in Taiwan created perovskite solar cells that effectively convert indoor lighting into electrical power.

“The most common solar cells in the market are silicon-based solar panels,” said author Fang-Chung Chen. “However, PeSCs can be made thin, lightweight, flexible, and even semi-transparent, whereas silicon panels are rigid and heavy, which limits their use to flat, durable surfaces.”

Previous research has shown that PeSCs can reach power conversion efficiencies comparable to silicon solar cells, but with the bonus of being able to work indoors. These PeSCs can be used to charge devices like remote controls, wearable devices, or trackers that can be connected to the internet.

To make a solar cell able to convert indoor light to energy, the researchers needed to tune the bandgap of the composition of the perovskite.

Bandgaps describe the minimum energy necessary for electrons to jump to higher energy levels, and different bandgaps can absorb different light wavelengths.

By adjusting the ratios of the molecules in the solutions used to make the perovskite layers of the solar cells, the researchers were able to achieve an optimal bandgap for absorbing indoor light. This bandgap adjustment is not something that can be done in silicon solar cells.

“The indoor efficiency of PeSCs is higher, meaning that the photovoltaic products can be more suitable for versatile user scenarios, including cloudy outdoor, indoor, and other dim-light environments,” said Chen.

“Tuning the bandgap, unfortunately, accompanies a negative effect: It brings defects in the perovskite layers,” said Chen. “To compensate for the loss in efficiency, we propose one method for fixing the defects.”

Under the one standard sun illumination (close to 12,000 lux), the team’s perovskite cells achieved a PCE of 12.7%, which, compared to some of the highest PCEs of silicon solar cells of 26%, isn’t much. However, the PeSCs displayed an impressive PCE of 38.7% under 2,000 lux, which is a fraction of the light that comes from the sun on a sunny day and is a similar brightness level to those found in offices.

To Chen’s surprise, their strategy for passivating the perovskite layer, which makes it less susceptible to corrosion, also improved the overall PeSC’s stability.

“In the beginning, we only expected our approach would improve the device efficiency,” said Chen. “Because the poor reliability of PeSCs is a large challenge for their adoption, we hope our proposed method can pave the way toward the commercialization of perovskite solar panels.”