Photoluminescence, time-resolved emission and photoresponse of plasma-modified porous silicon thin films

• Coating porous silicon (PS) by hydrocarbon (CHx) reduces nonradiative transition.
• Drop of the photoluminescence (PL) intensity.
• The PL of CHx/PS is due to radiative transitions at 1.8 and 1.87 eV.
• Photosensitivity revealed an excess spectral response (SR) at high-energy excitation.
• For photovoltaic PL and SR could be used for the evolution of the silicon solar cells.

Photoluminescence and photoelectrical study on plasma-modified porous silicon (PS) thin films is presented. Porous silicon passivated by hydrocarbon groups (CHx) shows an intense broad and stable photoluminescence (PL) band centered at 623 nm whereas the maximum of the photosensitivity spectrum is placed around 400 nm. Along with its potential utilization for silicon-based light emitters' fabrication, it could also represent an appealing option for the improvement of energy conversion efficiency in silicon-based solar cells whether by using its luminescence properties (photon down-conversion) or the excess photocurrent produced by an improved high-energy photon's absorption. Excitation spectra (PLE) under steady-state conditions are reported. PLE shows that visible PL is excited by light from UV region. The time-resolved photoluminescence of CHx/PS in the range of some tenth of μs are investigated at room temperature. The PL decay line shape, in CHx/PS is well described by stretched exponential. The photosensitivity spectroscopy shows a significant increase of absorption at high photon energy excitation.