Stable ultrathin surfactant-free surface-engineered silicon nanocrystal solar cells deposited at room temperature

We present a scalable technology at room temperature for the fabrication of ultrathin films based on surfactant-free surface-engineered silicon nanocrystals (SiNCs). Environmentally friendly pulsed fsec laser induced surface engineering of SiNCs and vacuum low-angle spray deposition is used to produce ultrathin films. Surface engineering of SiNCs improved stability and dispersibility of SiNCs by allowing thin (30 nm thickness) and exceptionally smooth (mean square roughness corresponds to 0.32 nm) film deposition at room temperature. The quality of the SiNC thin films is confirmed by ultrafast photoluminescence measurements and by applying such films for solar cells. We demonstrate that films produced with this approach yield good and stable devices. The methodology developed here is highly relevant for a very wide range of applications where the formation of high-quality ultrathin films of quantum dots with controllable thickness and smoothness is required.