Researchers Reimagine Material Science for Next-Gen Solar Cells

Solar cells are undoubtedly becoming more integral in the energy mix, yet they still have huge room to grow. One major concern is the low efficiency of existing cells on the market. Beyond that, current cells are limited by their structural rigidity, whereas more flexible solar cells could be better suited to emerging applications.

 

Solar-powered cars may be one application for flexible solar cells. Image used courtesy of Toyota

 

Recently, academic studies have marked major strides in solar cell efficiency and flexibility. Here’s a roundup of recent studies and how they’re pushing the state of the field.

 

Materials for Solar Cell Efficiency

Currently, the best solar cells available on the market have efficiencies of around 25%, meaning that nearly three-quarters of all incident solar energy is not effectively captured. One theoretical way to improve this efficiency is by creating multijunction solar cells. These devices join together multiple materials of different bandgaps to mitigate the carrier thermalization and non-absorption losses of conventional solar cells. Such a cell has a theoretical efficiency of over 50%, marking a significant improvement over current technologies.

 

Alloy absorption edge with varying concentrations of titanium. Image used courtesy of Kondrotas et al.

 

To actualize these improvements, a research team recently synthesized a new material. Using a solid state reaction, the group explored a variety of tin zirconium titanium selenide alloys [Sn(Zr1−xTix)Se3] alloys at varying ratios of titanium to zirconium. This chemical structure was chosen as it closely resembles the ABX3 structure of conventional perovskite materials. Through a series of tests, the group then evaluated the different structural, optical, and electrical characteristics of different alloy ratios. 

One major conclusion from the study was that the alloy had a structural stability limit up to a Ti/(Ti+Zr) ratio of 0.44. Additionally, they found that the higher the concentration of titanium, the more the absorption edge of the alloy shifted toward the infrared spectrum. The findings are significant because current solar cells don’t capture infrared light. Therefore, an alloy that absorbs this spectrum could lead to increased efficiencies. 

 

Strechable Solar Cells

The emergence of more human-centric electronic devices, such as wearables, has increased interest in stretchable electronics. With the potential to fit unique form factors, stretchable and flexible electronics could unlock a new wave of electronic devices.

As a part of this, interest is growing in developing sustainable solar cells capable of deforming significantly without sacrificing conversion efficiency.  Researchers from the Korea Advanced Institute of Science and Technology (KAIST) recently set a record for stretchable solar cells.

 

The structure of KAIST’s stretchable solar cell. Image used courtesy of Lee et al.

 

The group developed a unique polymer material from conjugated polymer donors consisting of electroactive rigid and soft blocks. With the specialized polymer material, the group created a solar cell capable of up to 40% deformation while still maintaining photovoltaic conversion efficiencies of up to 19%. Notably, this material could preserve up to 80% of its efficiency when stretched to 31% strain.

The researchers’ achievement marks a world record for efficiency at the given deformation for organic solar cells and could have huge implications for the future of sustainable wearable electronics.

 

Toward a Sustainable Future

As renewable energy grows in importance, studies in improving solar cell efficiency and more versatile, flexible cells are vital. Innovations in solar cell technology could have major implications for the efficacy and applicability of solar technology.