Coaxial multishell nanowires with high-quality electronic interfaces and tunable optical cavities for ultrathin photovoltaics

摘要: Abstract Silicon nanowires (NWs) could enable low-cost and efficient photovoltaics, though their performance has been limited by nonideal electrical characteristics an inability to tune absorption properties. We overcome these limitations through controlled synthesis of a series polymorphic core/multishell NWs with highly crystalline, hexagonally-faceted shells, well-defined coaxial (p/n) p/intrinsic/n (p/i/n) diode junctions. Designed 200–300 nm diameter p/i/n NW diodes exhibit ultralow leakage currents approximately 1 fA, open-circuit voltages fill-factors up 0.5 V 73%, respectively, under one-sun illumination. Single-NW wavelength-dependent photocurrent measurements reveal size-tunable optical resonances, external quantum efficiencies greater than unity, current densities double those for silicon films comparable thickness. In addition, finite-difference-time-domain simulations the measured structures agree quantitatively measurements, demonstrate that resonances are due Fabry-Perot whispering-gallery cavity modes supported in high-quality faceted nanostructures. Synthetically optimized devices achieve 17 mA/cm2 power-conversion 6%. Horizontal integration multiple demonstrates linear scaling absolute number NWs, as well retention high short-circuit single devices. Notably, assembly 2 elements into vertical stacks yields 25 backside reflector, further show such stacking represents attractive approach enhancing projected > 15% 1.2 μm thick 5 stacks.