The cross-sectionalmicrostructuresofamono-grainedCdSthin
film andofaCdTesolarcellfabricatedinourlaboratoryareshown
in Fig. 1. The5-mm-thick CdTeabsorberlayeriscomposedof
densely-packedCdTegrainswithdiametersof 1–3 mm, whichis
the optimumgrainsizeforhighefficient solarcellfabrication.The
CdS thin film consistsofamono-grainlayer.Suchamono-grain
layernotonlyenhanced Jsc but alsoallowedtheinter-diffusion
reactionattheCdS/CdTejunctioninterfacetobeundergood
control [6,7]. InaCdS/CdTesolarcell,duringthecell film deposi-
tion andpost-growthheattreatment,amixedCdSxTe1x inter-
facial layerisformedattheCdS/CdTeinterfacethrough
interdiffusion.Thisinterfaciallayerisgenerallybelievedtobe
beneficial forthecellefficiency.Throughinterfaciallayerforma-
tion, thelargelatticemismatchbetweenCdSandCdTeandthe
defect densityattheinterfacecanbegreatlyrelievedandreduced.
The highcrystallineCdTequalityaswellasthewellformedCdTe/
CdS heterojunctionresultedinroutinefabricationofCdTecells
with energyconversionefficiency of 12%andashort-circuit
currentdensityashighas 22 mA/cm2 in ourlaboratory.
The schematicbandstructureandtheequivalentelectriccircuit
diagramofaCdS/CdTehetero-structuresolarcellareshownin
Fig. 2. Theequivalentelectriccircuitequationcanbedescribedas