Solar cell design with over 60% efficiency

Japanese researchers have designed a solar cell with theoretical energy conversion efficiency of over 60%, in a breakthrough which could have a big impact on the cost of producing electricity. Their study has been published in the journal Nature Communications.

Solar cells convert the sun’s energy into electricity by converting photons into electrons. In theory, 30% energy conversion efficiency is the upper limit for traditional single-junction solar cells, as most of the solar energy that strikes the cell either passes through without being absorbed or becomes heat energy instead.

But this hasn’t stopped researchers all around the world from creating new solar cells looking to lift these limitations on conversion efficiency and reduce the loss of energy. The current world record is 46% for a 4-junction solar cell.

Researchers at Kobe University sought to increase this efficiency further, utilising two small photons from the energy transmitted through a single-junction solar cell containing a hetero-interface formed from semiconductors with different bandgaps. Using these photons, they developed a new solar cell structure for generating photocurrents.

By absorbing the spectral components of longer wavelengths that are usually lost during transmission through the cell, the new solar cell design achieved theoretical results of up to 63% conversion efficiency. Furthermore, the reduction in energy loss demonstrated by the experiment was over 100 times more effective compared to previous methods that used intermediate bands.

The team plan to continue designing solar cells and assess their performance based on conversion efficiency. They eventually hope to develop a highly efficient solar cell that will enable low-cost energy production.

Image caption: Theoretical prediction of conversion efficiency. The efficiency changes in response to the use of two different bandgaps in a hetero-interface. The highest conversion efficiency is 63%.