MOLYBDENUM BACK CONTACT ENGINEERING USING ULTRATHIN INTERMEDIATE LAYERS FOR SOLUTION PROCESSED Cu_2 (Zn,Cd) SnS_4 SOLAR CELLS

摘要

Sputter deposited ultrathin (～10nm) CuO and ZnS intermediate layers have been separately incorporated into solution processed Cd-doped Cu_2 (Zn,Cd) SnS_4 (CZCTS) thin film solar cells to suppress the diffusion of S during sulfurization and the formation of MoS_2 between the absorber and the Mo back contact. X-ray diffraction of sputtered Mo films with CuO and ZnS overlayers showed reduced MoS_2 formation after sulfurization at 600°C. However, CuO results in the lowest sheet resistance for the CuO/Mo bilayer after sulfurization. When introduced into a CZCTS/CdS device structure, the ultrathin CuO and ZnS layers can maintain good adhesion with the absorber layer due to an absence of voids in CZCTS near the back interface. Deposition of CZCTS onto CuO results in a reduction of the crystallite size while ZnS has the opposite effect. Elemental profiling of fabricated CZCTS/CdS solar cells showed reduced diffusion of S into Mo. As a result, CZCTS/CdS device with ZnS intermediate layer have higher power conversion efficiencies of 9.49% compared with the reference device of 8.84%.