It shows great potential to advance the development of next-generation high-efficiency solar cells, which are vital for meeting global energy needs. A team at Lehigh University has created a material that could significantly increase the efficiency of solar panels.

A prototype using this material as the active layer in a solar cell exhibits an average photoelectric absorption of 80%, a high rate of photoexcited carrier generation, and an unprecedented external quantum efficiency (EQE) of up to 190%; this is the figure so far. It exceeds the theoretical Shockley-Queisser efficiency limit for silicon-based materials and takes the field of quantum materials for photovoltaics to new heights.

“This study represents a significant step forward in our understanding and development of sustainable energy solutions, highlighting innovative approaches that could redefine solar energy efficiency and affordability in the near future,” said physics professor Chinedu Ekuma, who published a paper on the development of solar energy. Material featured in the journal by Lehigh doctoral student Srihari Kastuar Science Developments.

Advanced material properties

The jump in the material’s efficiency is largely due to different “hole states,” specific energy levels positioned in the material’s electronic structure in ways that make them ideal for solar energy conversion.

These states have energy levels of approximately 0.78 and 1.26 electron volts, within the optimal subband gaps, which are the energy ranges at which the material can efficiently absorb sunlight and produce charge carriers. Additionally, the material performs particularly well with high levels of absorption in the infrared and visible regions of the electromagnetic spectrum.

In conventional solar cells, the maximum EQE is 100%; This means that for every photon absorbed by sunlight, one electron is produced and collected. However, some advanced materials and configurations developed in the last few years have demonstrated the ability to generate and collect multiple electrons from high-energy photons, representing an EQE of over 100%.

Although such multiple exciton generation (MEG) materials have not yet been widely commercialized, they have the potential to significantly increase the efficiency of solar energy systems. Band gap states in the material developed by Lehigh allow capturing photon energy lost through reflection and heat generation in conventional solar cells.

Material development and potential

The researchers developed the new material by exploiting “van der Waals voids,” which are atomically small gaps between layered two-dimensional materials. These voids can confine molecules or ions, and materials scientists often use them to add or “interleave” other elements to tune the material’s properties.

To develop their new material, Lehigh researchers sandwiched zero-valent copper atoms between layers of a two-dimensional material composed of germanium selenide (GeSe) and tin sulfide (SnS).

“The rapid response and increased efficiency strongly demonstrate the potential of Cu-intercalated GeSe/SnS as a quantum material for use in advanced photovoltaic applications and offer a path to increase solar energy conversion efficiency,” he said. “It is a promising candidate for the development of next-generation high-efficiency solar cells that will play a critical role in meeting global energy needs.”

While integrating the newly developed quantum material into existing solar energy systems will require further research and development, Ekuma points out that the experimental techniques used to create these materials are already quite advanced. Over time, scientists mastered a method that precisely packs atoms, ions, and molecules into materials.