Characterization of Arsenic Doped CdTe Layers and Solar Cells

Polycrystalline CdTe solar cells with hole carrier-density greater than 10¹⁶ cm⁻³have been realized by doping the absorber with Arsenic. The high carrier concentration requires a large excess of Arsenic in the film implying only percent level doping activation. Appearance of a sub-bandgap peak in the photoluminescence (PL) spectrum is linked with the activation of the Arsenic dopant. Low temperature PL measurements confirm an acceptor level at 90 meV from the valence band, which is consistent with reported literature values. Additional features in the PL spectra suggests the presence of sub-band defects. Understanding the origin for these features may enable the high efficiency potential of group-V doping.