Optimization of the CdS optical window layer via cryogenic fabrication and its integration into CdS/CdTe solar cells
摘要
CdS thin films, used as optical windows in photovoltaic devices, were deposited on glass substrates using a custom-designed cryogenic system under high vacuum (10–6 Torr) at substrate temperatures between 100 and 300 K in 50 K intervals. XRD analysis confirmed the hexagonal crystal structure of all films without structural damage. FESEM images showed uniform, close-packed grain morphology at 200 K, characterized by equal-sized clusters (10–12 nm), indicative of soliton growth. This film also exhibited the highest optical transmittance (96%). Grain sizes ranged from 45 to 7.6 nm, corresponding to optical bandgap values between 2.41 and 2.46 eV. Electrical measurements revealed resistivity values between 6.1 × 103 and 7.3 × 103 Ω·cm and carrier concentrations from 3.4 × 1016 to 7.1 × 1015 cm−3. CdS layers produced at 200 K and 300 K were used to fabricate CdS/CdTe solar cells, where the 200 K sample achieved the highest photovoltaic efficiency of 9.44%.
Graphical abstract