Role of CdTe Interface Structure on CdS/CdTe Photovoltaic Device Performance

Glancing angle deposition (GLAD) of CdTe can produce a cubic, hexagonal, or mixed phase crystal structure depending upon the oblique deposition angles (phi) and substrate temperature. GLAD CdTe films are prepared at different phi at room temperature (RT) and a high temperature (HT) of 250 degrees C and used as interlayers between the n-type hexagonal CdS window layer and the p-type cubic CdTe absorber layer to investigate the role of interfacial tailoring at the CdS/CdTe heterojunction in photovoltaic (PV) device performance. The phi = 80 degrees RT GLAD CdTe interlayer and CdS both have the hexagonal structure, which reduces lattice mismatch at the CdS/CdTe interface and improves electronic quality at the heterojunction for device performance optimization. The device performance of HT CdS/CdTe solar cells with phi = 80 degrees RT with 50 to 350 nm thick GLAD CdTe interlayers is evaluated in which a 250 nm interlayer device shows the best device performance with a 0.53 V increase in open-circuit voltage and fill-factor product and a 0.73% increase in absolute efficiency compared to the HT baseline PV device without an interlayer.

Automated summary

Glancing angle deposition (GLAD) of CdTe can produce different crystal structures depending on the oblique deposition angles and substrate temperature. The use of GLAD CdTe interlayer at the CdS/CdTe heterojunction can improve device performance by reducing lattice mismatch and improving electronic quality at the interface. The device performance of HT CdS/CdTe solar cells is significantly improved with a GLAD CdTe interlayer at an oblique deposition angle of 80 degrees.