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Comparative Study of Al 2 O 3 and HfO 2 for Surface Passivation of Cu(In,Ga)Se 2 Thin Films: An Innovative Al 2 O 3 /HfO 2 Multistack Design
Author(s) -
Scaffidi Romain,
Buldu Dilara G.,
Brammertz Guy,
de Wild Jessica,
Kohl Thierry,
Birant Gizem,
Meuris Marc,
Poortmans Jef,
Flandre Denis,
Vermang Bart
Publication year - 2021
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.202100073
Subject(s) - passivation , copper indium gallium selenide solar cells , materials science , annealing (glass) , optoelectronics , solar cell , thin film , nanotechnology , layer (electronics) , metallurgy
In Cu(In,Ga)Se 2 (CIGS) thin‐film solar cells, interface recombination is one of the most important limiting factors with respect to device performance. Herein, metal–insulator–semiconductor samples are used to investigate and compare the passivation effects of Al 2 O 3 and HfO 2 at the interface with CIGS. Capacitance–voltage–frequency measurements allow to qualitatively and quantitatively assess the existence of high negative charge density ( Q f ≈ −10 12 cm −2 ) and low interface‐trap density ( D it ≈ 10 11 cm −2 eV −1 ). At the rear interface of CIGS solar cells, these, respectively, induce field‐effect and chemical passivation. A trade‐off is highlighted between stronger field‐effect for HfO 2 and lower interface‐trap density for Al 2 O 3 . This motivates the usage of Al 2 O 3 to induce chemical passivation at the front interface of CIGS solar cells but raises the issue of its processing compatibility with the buffer layer. Therefore, an innovative Al 2 O 3 /HfO 2 multistack design is proposed and investigated for the first time. Effective chemical passivation is similarly demonstrated for this novel design, suggesting potential decrease in recombination rate at the front interface in CIGS solar cells and increased efficiency. 300 °C annealing in N 2 environment enable to enhance passivation effectiveness by reducing D it while surface cleaning may reveal useful for alternative CIGS processing methods.