Type-II Quantum-Dot-Sensitized Solar Cell Spanning the Visible and Near-Infrared Spectrum

Type-II heterostructure CdTe/CdSe core/shell nanocrystals (quantum dots, QDs) are explored as sensitizers in a QD-sensitized photoelectrochemical solar cell. These QDs comprise a hole-localizing core and an electron-localizing shell. Among their advantages is the significant red shift of the absorption edge of the heterostructured QD relative to its two constituents due to spatially indirect absorption leading to improved absorption characteristics, intraparticle exciton dissociation upon photoexcitation, and a relatively small content of the less abundant tellurium element. Upon incorporation in a sensitized solar cell utilizing a porous TiO2 and a polysulfide electrolyte, these QDs exhibited efficient charge separation and high internal quantum efficiency despite hole localization in the CdTe core. Monochromatic incident photon-to-current conversion efficiency (IPCE) measurement shows a spectrally broad photoresponse spanning the whole visible spectrum and reaching up to similar to 900 nm.