Chinese scientists have unveiled a new type of solar battery capable of both capturing sunlight and storing electricity in one device.
The device, tested under simulated sunlight, achieved a solar-to-electricity conversion efficiency of 4.2 percent, representing a unified solution for light capture and energy storage.
Unlike traditional solar systems, which rely on separate photovoltaic panels and external batteries, this innovation merges both functions into a single electrochemical setup. The result is a battery that responds directly to sunlight, triggering chemical reactions that store energy, without converting it first into electricity for the grid.
Developed in Jiangsu province, the SRFB concept revives growing interest in photoelectrochemical energy storage. These systems are gaining traction as they offer a simplified, more integrated alternative to conventional solar setups. The team’s approach combines light absorption and chemical energy storage into one flow-based mechanism, potentially streamlining the solar storage process and reducing material complexity.
The device is built around a photocathode made from commercial triple-junction amorphous-silicon (3jn-a-Si) photovoltaic cells, which the researchers trimmed into 0.8-inch square sections. These cells consist of layered amorphous silicon–germanium alloy junctions mounted on a stainless-steel substrate, coated with indium tin oxide (ITO) to enhance conductivity, reports Interesting Engineering.
This photocathode was connected to a carbon-felt counter electrode through an external circuit and placed directly into a catholyte solution containing 2,6-DBEAQ, a compound from the anthraquinone family. On the other side, the system used an anolyte of K₄[Fe(CN)₆], which oxidizes at the counter electrode. Both fluids were kept in constant motion by a peristaltic pump, flowing through the battery cell while being separated by a Nafion ion-exchange membrane to maintain ionic balance and avoid mixing.
According to pv magazine, this design directly links light-triggered reactions to the flow of electrons within the battery, allowing sunlight alone to drive energy storage. The redox pair selection was key: the anthraquinone-based solution provided improved chemical stability and better resistance to photoelectrode corrosion, issues that had limited efficiency in earlier SRFB designs.
The research addresses a major challenge in SRFBs: maintaining stability while enabling effective light conversion. As explained by Chengyu He, corresponding author of the study, common redox systems such as AQDS and 2,6-DHAQ are often unstable under extreme pH conditions and contribute to degradation of the photoelectrode. These problems typically result in low output efficiency.
In contrast, the new system uses 2,6-DBEAQ specifically to enhance the compatibility between the electrolyte and the light-absorbing surface. This leads to more durable cycling and reduces the chemical strain placed on the core materials. The result is a more efficient process that can sustain multiple charge-discharge sequences without significant losses in performance.
Before initiating tests, the researchers purged the electrolytes with argon gas for 30 minutes to eliminate dissolved oxygen, preventing side reactions that could disrupt performance. This preparation allowed for clean measurement of the system’s performance over repeated cycles.
Testing was conducted under a xenon lamp simulating one sun, delivering 100 milliwatts per square centimeter. The SRFB was charged using only light, with no external electrical input, and then discharged at a current of 10 milliamperes per square centimeter. Across 10 full cycles, the device maintained a consistent solar-to-output electricity efficiency of 4.2 percent, a figure validated by the research.
According to the research team, this efficiency, though modest by photovoltaic standards, represents a functioning light-to-storage system that could serve as a foundation for further refinement. The direct coupling of solar input with storage output reduces complexity and opens new possibilities in solar-chemical technologies.
The scientists emphasize that the successful construction and operation of this SRFB marks a promising direction in the search for more compact, integrated renewable energy systems.
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