Silicon Surface Passivation by Al2O3: Recombination Parameters and Inversion Layer Solar Cells

Investigating the electronic properties of Al2O3/Cu(In,Ga)Se2 interface

“…These results reveal that the field-effect passivation due to negative fixed charges is activated only for post-deposition annealed Al 2 O 3 films, and that the extracted negative fixed charge density Q f is within a range similar to that observed on silicon surfaces. [9][10][11][12] This indicates that the field-effect passivation quality achieved by the PDA films on CIGS surfaces is comparable to that achieved by ALD Al 2 O 3 films on silicon surfaces. [9][10][11] Furthermore, due to the presence of highly negative Q f values in the PDA films, the net concentration of minority carriers (n s ) at the CIGS surface will be reduced, thereby satisfying one of the requirements to reduce the surface recombination rate (U s ) according to the Shockley-Read-Hall formalism.…”

“…[9][10][11][12] This indicates that the field-effect passivation quality achieved by the PDA films on CIGS surfaces is comparable to that achieved by ALD Al 2 O 3 films on silicon surfaces. [9][10][11] Furthermore, due to the presence of highly negative Q f values in the PDA films, the net concentration of minority carriers (n s ) at the CIGS surface will be reduced, thereby satisfying one of the requirements to reduce the surface recombination rate (U s ) according to the Shockley-Read-Hall formalism. 21,22 Another possibility for reducing U S is to reduce the interface trap charge density (D it ) at the Al 2 O 3 /CIGS interface, since it reflects the chemical passivation quality at the interface.…”

“…9,10 This passivation ability is attributed to a high density of negative Q f (10 12 -10 13 cm −2 ) in the Al 2 O 3 bulk (field-effect passivation) in combination with a low interface-trap charge density D it (10 10 -10 12 eV −1 cm −2 ) at the Al 2 O 3 /Silicon interface (chemical passivation). [9][10][11][12] Therefore, in the case of CIGS surface passivation by ALD Al 2 O 3 , experimentally extracting these electronic properties is important (i) to evaluate the passivation quality, and (ii) to understand the dominant passivation mechanism involved.…”

“…Indeed this can reduce the surface recombination rate to a great extent, depending on the magnitude and ratio of electron-to-hole capture cross-sections (σ n /σ p ) at the Al 2 O 3 /CIGS interface, reaching levels comparable to those obtained on p-type silicon surfaces with ALD Al 2 O 3 passivation. [9][10][11][12] The electronic properties of the ALD Al 2 O 3 /CIGS surfaces and interface have been experimentally extracted for the first time. On the basis of C-V and G-f measurements, the PDA films exhibit a high density of negative fixed charges in combination with slightly lower interface trap charges as compared to the AD films.…”

“…The concept of passivating CIGS surfaces using ALD Al 2 O 3 films is based on previous experience gained from silicon solar cell technologies. [9][10][11][12] The surface passivation of silicon substrates using ALD Al 2 O 3 films has drawn intense attention from the silicon photovoltaic community because of these films' ability to passivate p-and n-type as well as highly doped p + silicon surfaces effectively. 9,10 This passivation ability is attributed to a high density of negative Q f (10 12 -10 13 cm −2 ) in the Al 2 O 3 bulk (field-effect passivation) in combination with a low interface-trap charge density D it (10 10 -10 12 eV −1 cm −2 ) at the Al 2 O 3 /Silicon interface (chemical passivation).…”