Doping CdTe Absorber Cells using Group V Elements

Arsenic dopant was incorporated in CdTe absorber layers in high-efficiency CdTe cells using feedstock doped with 1018cc-1for sublimation of films. The goal of the work was to develop a feasible method for creating a hole density equal to, or greater than that currently achievable using copper doping using a CuCl treatment. Doping with arsenic resulted in a modest increase in open-circuit voltage (VOC) and a large improvement in fill-factor and conversion efficiency when compared with copper-doped devices with similar structure. All experiments were performed in the presence of cadmium overpressure to encourage dopant activation in tellurium vacancy sites. Arsenic incorporation was measured using Secondary Ion Mass Spectrometry (SIMS) at 4E +16 atoms/cc-1,about four times greater incorporation than previously seen by the authors. Using a CdSeTe/CdTe graded absorber and arsenic doping, a conversion efficiency of 16.79% was achieved.