Doo Youl Lee

Back contact formation using Cu2Te as a Cu-doping source and as an electrode in CdTe solar cells

Cu2Te was utilized as a Cu source for p + doping in CdTe and as a primary back contact material in CdTe solar cells. A 60 nm-thick Cu2Te layer was deposited on CdTe film by evaporating Cu2Te and the samples were annealed at various temperatures. An amorphous layer was found at the Cu2Te/CdTe interface, while the Cu2Te has both orthorhombic and hexagonal phases. Annealing at 2001C completely crystallized the amorphous interlayer and enhanced the transformation of orthorhombic phase into hexagonal phase that has a coherent interface with CdTe. A good p + contact was formed at 1801C annealing, where the series

Characterization of Cu-poor surface on Cu-rich CuInSe2 film prepared by evaporating binary selenide compounds and its effect on solar efficiency

Abstract Binary selenide compounds, In 2 Se 3 and Cu 2 Se, were employed in a three-stage co-evaporation process to prepare CuInSe 2 films. The composition and thickness of Cu-poor regions on Cu-rich CIS film were varied by the evaporation rate of In 2 Se 3 and Se in the third stage. The Cu-poor regions were indistinguishable from CuInSe 2 film in microstructure and were precisely characterized by Auger electron microscopy, microenergy dispersive X-ray spectroscopy, and Rutherford backscattering spectroscopy. A 9.25% efficiency in an active area of 0.16 cm 2 was achieved by inverting the surface of CuInSe 2 film from Cu-rich composition to In-rich composition. Introducing 100-nm-thick CuIn 3 Se 5 onto the surface of Cu-rich CuInSe 2 film increased the cell efficiency to 9.59%, due to the increased fill factor and open circuit voltage. A lowering of the interface recombination current at the CdS/CuInSe 2 was attributed to the improved cell efficiency.

Formation of p/sup +/ CdTe contact with Cu/sub 2/Te electrode and its stability in CdTe cells

Cu/sub 2/Te electrode was utilized as a Cu source to form p/sup +/-CdTe and its stability in CdTe cells has been investigated. An amorphous interlayer was found at the CdTe/Cu/sub 2/Te interface by depositing Cu/sub 2/Te at room temperature and it was crystallized by annealing at 200/spl deg/C, enhancing the growth of hexagonal phase compared to orthorhombic phase. A good p/sup +/ ohmic contact was formed at 180/spl deg/C annealing and the best efficiency was obtained at 200/spl deg/C. The cell efficiency was degraded under forward bias and it was either improved or recovered both under reverse bias and by additional annealing, The cell with thinner CdTe layer was degraded faster and more severely affected by bias stress.