Vapor Transport Deposition and Characterization of Polycrystalline CdTe Solar Absorbers

摘要

Vapor transport deposition is being developed for high-rate synthesis of CdTe thin films. Films have been deposited at rates in excess of 20 μm/min. The growth rate dependence on source temperature yielded an apparent activation energy of 42 kcal/mol, in good agreement with the theoretical value for CdTe sublimation (45.7 kcal/mol). For substrate temperatures greater than 400℃ the rate limiting step was resublimation. This phenomenon had a dramatic influence on morphology, although x-ray diffraction of all firms indicated a strong (111) orientation. A preliminary device optimization investigating the effect of CdTe deposition temperature, post-deposition CdCl_2 anneal parameters, alternative back contacts, and high-resistance buffer layers yielded a best cell with efficiency of 9.8% (704 mV V_(oc), 21.0 mA/cm2 J_(sc), 66% FF).