According to new research led by chemist Xiaoyang Zhu at the University of Texas at Austin, the efficiency of conventional solar cells could be significantly increased by making use of a quantum "shadow state" in an organic plastic semiconductor material.

The maximum theoretical efficiency of the silicon solar cells in use today is approximately 31%, because much of the sun’s energy hitting the cell is too high to be turned into usable electricity. That energy, in the form of "hot electrons," is lost as heat.

Zhu and his team previously demonstrated that those hot electrons could theoretically be captured using semiconductor nanocrystals but the actual implementation of a technology to do this would be very difficult and would require highly focused sunlight..

The researchers have now discovered that, in the organic plastic semiconductor pentacene, a photon produces a dark quantum "shadow state" from which two electrons can be efficiently captured to generate more energy. Exploiting that mechanism could increase solar cell efficiency to 44% using a low-cost plastic semiconductor without the need for focusing the solar beam.