Premium
Characterization of Interface Between Accurately Controlled Cu‐Deficient Layer and Cu(In,Ga)Se 2 Absorber for Cu(In,Ga)Se 2 Solar Cells
Author(s) -
Nishimura Takahito,
Sugiura Hiroki,
Nakada Kazuyoshi,
Yamada Akira
Publication year - 2018
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.201800129
Subject(s) - copper indium gallium selenide solar cells , dangling bond , annealing (glass) , band gap , materials science , solar cell , chemistry , optoelectronics , analytical chemistry (journal) , crystallography , silicon , metallurgy , chromatography
We recently succeeded in controlling a Cu‐deficient Cu(In,Ga)Se 2 layer (CDL) on a Cu(In,Ga)Se 2 (CIGS) surface by introducing an Se irradiation after the completion of the second stage in a three‐stage process during CIGS growth. The CDL on the surface causes the formation of a valence band offset (Δ E V ) between the CDL and CIGS because the Cu vacancies decrease the valence band maximum of the CDL. Therefore, we can expect the suppression of recombination at the CdS/CIGS interface in CIGS solar cells due to the repelling of holes by Δ E V . The amount of knowledge regarding the properties of CDL/CIGS interfaces is observed to be quite small because a control technique for CDL has not been developed so far. In this study, the compositional and structural properties of an accurately controlled CDL/CIGS interface are investigated in detail. The composition of the interface between the CDL and CIGS is observed using an energy dispersive X‐ray spectroscopy with the help of a transmission electron microscope. Using nanobeam electron diffraction and Fourier transfer mapping analysis, it is confirmed that the ( 1 1 ¯ 2 ) plane in the CDL continuously grows on the ( 11 2 ¯ ) plane in CIGS. Further, these results indicate that a high‐quality interface is formed between the CDL and CIGS, which contains only a small amount of dangling bonds. Finally, a high conversion efficiency of 19.4% is achieved in the CIGS solar cell, which can be attributed to the formation of CDL and effect of Δ E V .