Dr Lefteris Danos of Lancaster’s Chemistry Department has recently led a paper reviewing the development of photosensitised silicon solar cells, a technology that merges the robustness of silicon with the light-harvesting ability of molecular dyes.

Within the paper published as a feature article in Chemical Communications, Dr Danos and his fellow researchers Dr Liping Fang (Shenzhen MSU-BIT University), Professor Dr Branislav Dzurňak (Czech Technical University), Dr Pattareeya Damrongsak (King Mongkut’s Institute of Technology Ladkrabang, Thailand), Professor Dieter Meissner (LIOS, Johannes Keppler University, Austria), and Professor Tom Markvart (University of Southampton) review the crystalline silicon solar cells that currently dominate in the photovoltaics (PV) market, highlighting that if we wish to completely eliminate CO₂ emissions, the industry would need to increase PV’s energy production by 100 times and revolutionise the manufacture of these solar cells. The industrial production of silicon needed for PV components is incredibly energy-intensive and requires a substantial amount of electricity as a part of the process – electricity which is currently derived from fossil fuels, adding to our global carbon footprint.

The researchers therefore examine photosensitised silicon solar cells as an alternative PV technology, requiring less silicon than standard crystalline silicon solar cells. Photosensitised silicon solar cells use light-absorbing dye or quantum dots (tiny semiconductor nanocrystals) to improve the performance of silicon as a semiconductor. This technique is used to enhance light harvesting, especially in the visible light spectrum, where silicon’s absorption is suboptimal. Unlike currently available silicon solar cells, which absorb sunlight and separate charges simultaneously, photosensitised silicon separates this process into two. The dye or quantum dots on the surface absorb sunlight, using the photons in sunlight to excite electrons through a process called “exciton diffusion”. The energy of these excited electrons is then injected into the surface of the silicon, producing charge carriers in silicon that lead to electrical power generation.

By borrowing concepts from photosynthesis, the team explore how light energy can be captured and transferred at the nanoscale, improving the interaction between molecules and silicon surfaces. This innovative approach brings us closer to creating high-efficiency, low-cost solar devices inspired by nature’s own energy conversion systems. Whilst further research into this technology is required to manufacture such cells on a large or industrial scale, the authors highlight the importance of photosensitised silicon solar cells in the pursuit of next-generation solar energy technologies and hybrid electric devices.

On the publication of the paper, Dr Danos said: “Our vision is to develop a new generation of solar cells that use up to a hundred times less silicon and rely on light-harvesting molecules to capture sunlight. This approach separates the photovoltaic process into two steps - light absorption by the molecular layer and electricity generation in an ultra-thin silicon layer. By using recycled silicon, we hope to make solar energy production not only more efficient but also more sustainable, reducing the environmental impact of traditional silicon manufacturing.”

DOI: 10.1039/d5cc02567b