We report on the development of Mo/CdTe/CdS/indium-tin-oxide, thin-film solar cells grown by radio-frequency magnetron sputtering. This is an inverted configuration compared to the conventional glass/tin-oxide/CdS/CdTe/metal cells. Molybdenum was chosen as a substrate because its thermal expansion coefficient and the work function are close to those of CdTe. We have achieved AM1.5 conversion efficiencies of 7.8 percent on 0.05 cm2 area devices. Our best cells had a nitrogen-doped ZnTe layer between the molybdenum and the CdTe for a somewhat improved back contact. However, we observe a significant rollover in the IV curve in forward current that indicates a back-diode effect. This implies the need for improvement of the electronic properties of the molybdenum - CdTe and possibly CdS - ITO interfaces.
In this paper we describe the fabrication of amorphous SiC:H materials and using them as photoelectrodes in photoelectrochemical cells (PEC). With the increase of CH 4 flow (in SiH 4 gas mixture) during growth, the bandgap, Eg, increases from ~ 1.8eV to ~2.0eV, while the photoconductivity decreases from ~10 -5 S/cm to ~10 -8 S/cm. These highquality a-SiC:H materials with Eg of 2.0eV included into a solar cell configuration led to a conversion efficiency,η ~7% on textured Asahi U type SnO 2 coated substrates, with the i-layer thickness of ~300nm. For a reduced i-layer thickness of ~100 nm, a current density, J sc ~8.45mA/cm 2 has been achieved, Immersing the a-SiC:H(p)/a-SiC:H(i) structure in 0.33M H 3 PO 4 electrolytes, produced a photocurrent of ~7mA/cm 2 . With a further optimization we expect that the photocurrent could exceed 9mA/cm 2 . With the use of this configuration substrate/silicon tandem device (a-Si/a-Si or aSi/nc-Si)/a-SiC:H(p)/a-SiC:H(i), it may therefore be possible to increase the solar-to-hydrogen (STH) efficiencies to beyond 10%.
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