Microstructural Passivation of Patterned Al 2 O 3 Back Contacts on CdS/CdTe Solar Cells

Roy, Etee Kawna; Mamun, Ashraful; Lee, Chungho; Xiong, Gang; Yoon, Heayoung P.

doi:10.1002/admi.202400501

Title: Microstructural Passivation of Patterned Al ₂ O ₃ Back Contacts on CdS/CdTe Solar Cells

Journal Article · 24 September 2024 · Advanced Materials Interfaces

DOI: https://doi.org/10.1002/admi.202400501 · OSTI ID:2483736

Roy, Etee Kawna ^[1]; Mamun, Ashraful ^[1]; Lee, Chungho ^[2]; Xiong, Gang ^[2];

^[1]

Department of Electrical and Computer Engineering University of Utah Salt Lake City UT 84112 USA
California Technology Center First Solar Inc Santa Clara CA 95050 USA

Abstract Patterned aluminum oxide (Al ₂ O ₃ ) back contact on cadmium telluride (CdTe) solar cells can effectively mitigate the loss of the majority carriers while retaining the passivation benefits for minority carriers. This study investigates the impact of the point‐contact geometry on cell performance, where the spacing of the microholes is systematically varied at a constant microhole diameter (≈16 µm). Microhole arrays are created on an evaporated Al ₂ O ₃ layer (≈30 nm) on CdTe using laser‐beam lithography and selective wet etching processes. Comparative analysis indicates a significant decrease in fill factor (FF) and short‐circuit current ( I _SC ) when the contact fraction falls below 30%, likely due to the Al ₂ O ₃ barrier impeding majority carriers. Above this fraction, FF and I _SC are comparable to those of baseline CdTe cells without Al ₂ O ₃ . Open‐circuit voltage ( V _OC ) shows a gradual decrease as Al ₂ O ₃ coverage is reduced but exhibits a slight increase (<15 mV) when the contact fraction exceeds 30%. Cathodoluminescence (CL) characterization reveals that significantly improved radiative recombination occurs within the CdTe grain bulk with Al ₂ O ₃ , whereas this effect on grain boundaries is minimal. The findings imply complex local carrier dynamics in the patterned back‐contact region, closely tied to the microstructural properties of CdTe‐based solar cells.

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Sponsoring Organization:: USDOE

OSTI ID:: 2483736

Journal Information:: Advanced Materials Interfaces, Journal Name: Advanced Materials Interfaces Journal Issue: 35 Vol. 11; ISSN 2196-7350

Publisher:: Wiley Blackwell (John Wiley & Sons)Copyright Statement

Country of Publication:: Germany

Language:: English

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