Semiconducting silicon-tin alloy nanocrystals with direct bandgap behavior for photovoltaic devices

The feasibility of using surfactant-free semiconducting silicon-tin alloy nanocrystals with quantum confinement effect for photovoltaics is demonstrated. Synthetized nanoparticles with average of 3Â nm in diameter and optical bandgap of 0.81Â eV at room temperature were obtained. X-ray diffraction measurements with synchrotron radiation have confirmed a Si0.88Sn0.12 alloyed composition that corresponds to a ratio of about eight Si atoms for every Sn atom. Fourier transform infrared spectroscopy revealed a reduced surface oxygen concentration compared with elemental silicon nanocrystals. Furthermore the potential of silicon-tin nanocrystals as a photovoltaic material is assessed and an enhancement of the solar cells performance is demonstrated due to the extended spectral range and increased absorption. In particular, the short circuit current density has shown improvements as the concentration of silicon-tin nanocrystals is increased.