Light trick helps solar panels absorb energy 10,000 times better

Researchers trapped photons on tiny bumps near silicon, enhancing light interaction and improving absorption and device performance.

Jijo Malayil

Representational image: The new discovery enables manufacturing of ultrathin solar panels, advanced optoelectronics.

MIT

Researchers have developed a new method for light and matter interaction, paving the way for the production of ultrathin silicon solar cells.

The University of California, Irvine (UC Irvine) team’s study is based on previous work related to the transformation of pure silicon from an indirect bandgap semiconductor to a direct bandgap one by altering its interaction with light.

They transformed light interactions with silicon by trapping photons, enhancing absorption by 10,000 times, and improving device performance without changing the material’s chemistry.

The team highlights that the discovery may contribute to the expansion of energy-converting technology into a wide range of uses, such as onboard car and device charging and thermoelectric apparel.

In the new study, researchers used a new method that involved changing the light instead of the material.

They trapped photons on very small bumps near the silicon, giving the light new properties that enhanced its interaction with the material. By modifying the surface of the silicon, they greatly improved how much light is absorbed and significantly boosted the devices’ performance.

Photons lack the momentum needed to trigger indirect optical transitions in semiconductors like silicon, which means they rely on lattice phonons to maintain momentum. This characteristic makes silicon less desirable than direct bandgap semiconductors for many optoelectronic applications.

As an indirect bandgap semiconductor, silicon’s limited optical properties hinder advancements in solar energy conversion and optoelectronics. This is a significant drawback, given that silicon is the second-most abundant element in Earth’s crust and serves as the foundation for the global computer and electronics industries.

“Photons carry energy but almost no momentum, but if we change this narrative explained in textbooks and somehow give photons momentum, we can excite electrons without needing additional particles,” said Eric Potma, professor of chemistry at UC Irvine and co-author of the study, in a statement.

This simplifies the interaction to just two particles: a photon and an electron, akin to what happens in direct bandgap semiconductors. This approach enhances light absorption by a factor of 10,000, fundamentally changing how light and matter interact without altering the material’s chemistry.

The new phenomenon fundamentally alters the interaction between light and matter. According to researchers, traditionally, textbooks describe vertical optical transitions, where a material absorbs light, causing the photon to change only the electron’s energy state.

However, momentum-enhanced photons can modify both the energy and momentum states of electrons, revealing new transition pathways previously unconsidered.

“Figuratively speaking, we can ‘tilt the textbook,’ as these photons enable diagonal transitions. This dramatically impacts a material’s ability to absorb or emit light,” said Ara Apkarian, distinguished professor emeritus of chemistry at UC Irvine and co-author of the study.

The researchers highlight that this development presents an opportunity to leverage recent advancements in semiconductor fabrication techniques at the sub-1.5-nanometer scale, which could significantly impact photo-sensing and light-energy conversion technologies.

With the increasing effects of climate change, transitioning from fossil fuels to renewable energy has become more urgent. Solar energy plays a crucial role in this shift, but current commercial solar cells are inadequate.

Silicon’s limited ability to absorb light necessitates thick layers—almost 200 micrometers of pure crystalline material—to capture sunlight effectively. This not only raises production costs but also reduces efficiency due to increased charge carrier recombination.

According to researchers, the thin-film solar cells made more feasible by this research are widely regarded as a solution to these issues.

The details of the team’s research were published in the journal ACS Nano.

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Jijo Malayil Jijo is an automotive and business journalist based in India. Armed with a BA in History (Honors) from St. Stephen's College, Delhi University, and a PG diploma in Journalism from the Indian Institute of Mass Communication, Delhi, he has worked for news agencies, national newspapers, and automotive magazines. In his spare time, he likes to go off-roading, engage in political discourse, travel, and teach languages.

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