Lattice mismatch alleviation in p-CdTe/n-Si heterostructure by surface engineering on Si substrate

Mustapha Isah; Camellia Doroody; Kazi Sajedur Rahman; Muhammad Najib Harif; Tiong Sieh Kiong; Ahmad Wafi Mahmood Zuhdi

doi:10.1016/j.heliyon.2023.e21536

Lattice mismatch alleviation in p-CdTe/n-Si heterostructure by surface engineering on Si substrate

Heliyon. 2023 Oct 31;9(11):e21536. doi: 10.1016/j.heliyon.2023.e21536. eCollection 2023 Nov.

Authors

Mustapha Isah^{1

2}, Camellia Doroody^{1

3}, Kazi Sajedur Rahman⁴, Muhammad Najib Harif^{1

5}, Tiong Sieh Kiong^{1

3}, Ahmad Wafi Mahmood Zuhdi^{1

3}

Affiliations

¹ Institute of Sustainable Energy (ISE), Universiti Tenaga Nasional (@The Energy University), Jalan Ikram-Uniten, 43000, Kajang, Selangor, Malaysia.
² Department of Physics, Kaduna State University, PMB, 2339, Tafawa Balewa Way, Kaduna State, Nigeria.
³ College of Engineering, Universiti Tenaga Nasional (@The Energy University), Jalan Ikram-Uniten, 43000, Kajang, Selangor, Malaysia.
⁴ Solar Energy Research Institute, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor, Malaysia.
⁵ Faculty of Applied Sciences, Universiti Teknologi MARA (UiTM), Cawangan Negeri Sembilan, 72000, Kuala Pilah, Negeri Sembilan, Malaysia.

Abstract

The study used magnetron sputtering to investigate the growth of cadmium telluride (CdTe) thin films on surface treated n-type silicon (n-Si) substrates. The n-Si substrates were textured using potassium hydroxide (KOH) before the sputter deposition of CdTe. This was followed by cadmium chloride treatment to reduce the strain at the interface of CdTe and Si, which is caused by the incompatible lattice and thermal expansion mismatch (CTE). X-ray diffraction (XRD) analysis showed that the lowest FWHM and dislocation densities were obtained for CdCl₂/CdTe/txt-nSi, which aligns with the scanning electron microscopy (SEM) results. In the SEM images, the interface bonding between the CdTe and Si surfaces was visible in the cross-sections, and the top-view images revealed sputtered CdTe thin films conforming to the patterns of pyramidal textured Si as an engineered surface to capture more light to maximize absorption in the CdTe/Si tandem design. The Energy dispersive X-ray (EDX) results showed that all the CdTe deposited on textured n-Si exhibited more Te atoms than Cd atoms, irrespective of the CdCl₂ treatment. The presented results suggest that the texturization and CdCl₂ treatment improved the morphology and grain boundary passivation of the sputtered CdTe. The adhesiveness of CdTe on the n-Si substrate was also significantly enhanced. Our findings further demonstrate that proper surface treatment of the Si substrate can greatly improve the quality of CdTe grown on Si by reducing the strain that occurs during the growth process. This study demonstrates a valuable method for enhancing the integration of CdTe with Si for two-junction tandem solar cell applications.

Keywords: CdCl2 treatment; CdTe; CdTe/Si heterostructure; Energy; KOH texturization; Lattice mismatch; Photovoltaics; Thermal mismatch; n-Si.