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HL: Fachverband Halbleiterphysik

HL 12: Photovoltaic

HL 12.5: Vortrag

Montag, 25. Februar 2008, 15:00–15:15, EW 202

Influence of gap state defect passivation on transport properties in SiO₂/Si/SiO₂ quantum layers — •Daniel Sixtensson, Bert Stegemann, and Manfred Schmidt — Hahn-Meitner-Institut Berlin, Abt. Silizium-Photovoltaik, Kekuléstraße 5, 12489 Berlin

The maximum efficiency of standard silicon single bandgap photovoltaic devices is given by the Shockley-Queisser limit of 32.7 %. A major loss source is thermalization of hot photogenerated charge carriers. Novel methods utilizing quantum confinement effects have recently been proposed to circumvent this limit. Si/SiO₂ quantum well structures, utilizing stacked absorbers with different bandgaps, can better be adjusted to the solar spectrum and thus, avoid thermalization losses. However, the interface-to-volume ratio increases tremendously in such structures. Therefore, due to strong interface recombination and Coulomb scattering from charged interface states, the Si/SiO₂ interfaces are a major factor limiting carrier transport. In the present work, the impact of defect passivation by hydrogen treatment on interface gap state defect densities at structurally and chemically well-defined Si/SiO₂ interfaces has been analyzed using surface photovoltage (SPV) measurements and constant final state photoelectron spectroscopy. Moreover, transport properties in single SiO₂/Si/SiO₂ quantum well structures are analyzed and related to interface quality by means of highly sensitive photoconductivity measurements.