Strong low-temperature anti-Stokes photoluminescence from coupled silicon nanocrystals

Abstract We report efficient low-temperature anti-Stokes photoluminescence (upconverted photoluminescence=UPL) at resonant excitation of coupled silicon nanocrystals (NCs) in porous silicon (PSi). This photoluminescence is absent in strongly oxidized porous silicon and oxidized silicon nanocrystals. The UPL is a result of resonant excitation of electron–hole (e–h) pairs spatially separated in neighboring crystals with different band-gap. It is generated by the excitation of a second e–h pair in the larger of the two crystals and Auger ejection of a carrier into the smaller one, with the larger band-gap.