PIE - Programme Interdisciplinaire Energie 2010-2013

The STEP-UP project aims to significantly reduce the cost per watt of thin film photovoltaics by breaking one of the fundamental links between fabrication speed and device quality. In a sinusoidallly driven RF-PECVD system, the injected power (influencing deposition speed) and ion bombardment (influencing film quality) are fundamentally linked. However, by tailoring the waveform and using a non-sinusoidal excitation, this link can be broken. By using a trapezoidal signal, such as extremely short pulses with rapid rise times, efficient power coupling can be obtained with a very small sheath potential on the deposition surface. The project will explore the applicability of the waveform tailoring concept in the deposition of thin films of nanocrystalline silicon for photovoltaics. In doing so, it will examine all aspects of the process : the active spectral correction of the trapezoidal waveform to correct for system distortion, the in-situ observation of the effect of the waveform on film-deposition, diagnostics of the plasma properties during trapezoidal excitation, plasma modelling for deeper understanding of unobservable effects of the waveform, and ex-situ optoelectronic film and device characterization. The complementary expertises of the two teams implicated in the project – LPICM on thin-film device fabrication and characterization, and LPP on plasma physics – is a significant driving force towards the success of the project.