Nitrogen doped Cu2O: A possible material for intermediate band solar cells?

The optical properties of sputtered Cu2O thin films doped with the nitrogen concentrations between 1 and 2.5 at% have been investigated by spectrophotometric measurements. All the doped samples exhibit two clearly defined absorption bands at energies below the gap, with an intensity well correlated with the N concentration. This result suggests Cu2O as a promising material for the development of intermediate band solar cells, also considering the band gap of about 2 eV which is the optimal value for this kind of devices. Moreover, the sample with the highest doping shows a resistivity of 1.14Ωcm, which is the lowest value ever reported for this semiconductor. As a collateral result, we provide a first estimation of the Relative Sensitivity Factors (RSF) of nitrogen and oxygen atoms under Cs+Cs+ bombardment in a Cu2O matrix.

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► Cu2O thin films with increasing N doping are grown by RF magnetron sputtering.
► The doping level is found to increase almost linearly with the N2 flux during the sputtering process.
► Two clear absorption bands are observed below the energy gap, at about 0.45 eV and 0.72 eV.
► The intensity of these absorption bands are well correlated with the N concentration.
► The highest doped sample (2.54 at%) shows a resistivity of 1.14Ωcm, which is the lowest value ever reported for Cu2O.