Size-dependent Photovoltaic Properties of Solar Cells Containing Si Quantum Dots/SiC Multilayers

Recently, many kinds of Si nanostructures have been extensively investigated, in which, Si quantum dot (Si QD) is one of the potential candidates for all-Si tandem solar cells. Because the optical bandgap of Si QDs can be tunable via size controlling, it can match the solar spectrum in a wide range and consequently improve the spectral response. In this work, Si QDs/SiC multilayers with controllable dot sizes were fabricated and characterized. The Raman spectra and transmission electron microscopy (TEM) observation revealed the formation of size-controllable Si QDs. The absorption measurement showed that the bandgap of Si QDs was red shifted to the long wavelength range with the dot size increasing, which agrees well with the quantum confinement effect. Moreover, heterojunction solar cells containing different sized-Si QDs/SiC multilayers were proposed and investigated. The solar cells exhibited strong size-dependent photovoltaic properties and the best cell had the power conversion efficiency (PCE) of 7.27%. Furthermore, the external quantum efficiency (EQE) measurement demonstrated the Si QDs contribution of light absorption and response in ultraviolet-visible range, which provides a promising way to realize better spectral match by applying different sized-Si QDs in the future photovoltaic devices.