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Band gap engineering of atomic layer deposited Zn x Sn 1‐x O buffer for efficient Cu(In,Ga)Se 2 solar cell
Author(s) -
Agbenyeke Raphael Edem,
Song Soomin,
Park Bo Keun,
Kim Gun Hwan,
Yun Jae Ho,
Chung TaekMo,
Kim Chang Gyoun,
Han Jeong Hwan
Publication year - 2018
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.3012
Subject(s) - band gap , materials science , copper indium gallium selenide solar cells , x ray photoelectron spectroscopy , solar cell , atomic layer deposition , band offset , analytical chemistry (journal) , ternary operation , thin film , layer (electronics) , optoelectronics , nanotechnology , chemistry , chemical engineering , valence band , chromatography , computer science , engineering , programming language
Ternary zinc tin oxide (ZTO) is one of the few environmental compatible buffer materials with the potential of replacing the n ‐CdS buffer in Cu(In,Ga)Se 2 (CIGS) solar cells and other photovoltaic systems once its properties are fully understood and optimized. In this work, ZTO films were grown by atomic layer deposition and were logically characterized with the aim of understanding the correlations between compositional changes and film properties. The ZnO:SnO 2 pulse ratio significantly affected the growth rate, crystal structure, morphology, and band gap of the ZTO films. By controlling the Sn/(Sn + Zn) atomic ratio, the optical band gap of the ZTO films was tuned between 3.05 and 3.36 eV. Integrating the ZTO films as buffer layers in CIGS solar cells, we observed that films with Sn concentrations of 9 to 16 at.% yielded photo‐conversion efficiency close to 14%, which was very comparable to efficiency attained with the commonly used CdS buffer. Furthermore, using X‐ray photoelectron spectroscopy analysis, we correlated the current‐voltage behavior of the cells to the conduction band offset at the ZTO/ CIGS interface.