Structural, optical and electrical properties of silicon nanocrystals fabricated by ICPCVD for next generation photovoltaics

Effects like quantum confinement, multiexciton per incident photon and Stokes shift have prompted extensive research of silicon at nanoscale dimensions for potential application in next generation photovoltaics. Such effects are highly size-dependent, implying that a viable fabrication method and thorough understanding of size-related properties are essential for device applications. In this report, we present new results on fabrication and characterization of silicon nanocrystals (Si-NCs) for application in solar cells. Si-NCs were fabricated by Inductively Coupled Plasma CVD (ICPCVD) using SiO₂/SiO_x<;2 superlattice approach. HRTEM imaging shows that ICPCVD is an excellent route for realizing tight size-controlled Si-NCs. Optical absorption measurements showed the optical bandgap tunability of Si-NCs. Stokes shift in absorption and emission was observed which could be exploited for down-shifter application in photovoltaics. Charge conduction mechanisms in the devices were studied. Ohmic behavior was observed in the low voltage regime (V_S <; 0.59 V) whereas Trap Assisted Tunneling was observed in high voltage regime (1.03 V <; V_S <; 4 V).