Omnidirectional absorption enhancement of symmetry-broken crescent-deformed single-nanowire photovoltaic cells

Single semiconductor nanowires enable a diverse range of applications in sensing, photodetection, and photovoltaics. Here we report that a delicate modification to the circular cross-section by eliminating a nanocrescent part can substantially strengthen the light-harvesting capability of a single nanowire. Despite the reduced photoactive material, the photocurrent density of the symmetry-broken crescent-deformed free-standing silicon single-nanowire solar cell can be counter-intuitively improved by over 45%. The excellent light-harvesting ability of the crescent-deformed nanowire can be maintained over a broad spectral band at a wide range of incident angle as corroborated by its dispersion relation. Under assistance of a metallic back reflector, the photocurrent enhancement ratio can be up to 66.2% without taking into account the material reduction. Our electrical evaluation shows that the new design leads to an enhancement ratio of light-conversion efficiency by 40.8%. This novel design by breaking structure symmetry represents a new pathway to realize highly efficient and compact photovoltaic devices with omnidirectional light absorption enhancement.