Optoelectronic Inactivity of Dislocations in Cu(In,Ga)Se₂ Thin Films

Abstract

High-efficiency Cu(In,Ga)Se 2 (CIGS) thin-film solar cells are based on polycrystalline CIGS absorber layers, which contain grain boundaries, stacking faults, and dislocations. While planar defects in CIGS layers have been investigated extensively, little is still known about the impact of dislocations on optoelectronic properties of CIGS absorbers. Herein, evidence for an optoelectronic inactivity of dislocations in these thin films is given, in contrast to the situation at grain boundaries. This unique behavior is explained by the extensive elemental redistribution detected around dislocation cores, which is connected with the dislocation strain field, probably leading to a shift of defect states toward the band edges.

Evidence of Cationic Antiphase Disorder in Epitaxial Cu(In,Ga)S2 Grown on GaP/Si(001)

“…Indeed, in CAPD, the S anionic sublattice stays relatively unaffected, and anion‐to‐cation ordering is satisfied. CAPD has been experimentally observed in epitaxial Cu(In,Ga)Se 2 , MgFe 2 O 4 , and SrTiO 3 :Sn grown on GaAs, [ 17,18 ] MgO(001), [ 25 ] and SrTiO 3 respectively, and in other types of materials like MgAl 2 O 4 and BeAl 2 O 4 . [ 26 ]…”

“…Indeed, in CAPD, the S anionic sublattice stays relatively unaffected, and anion-to-cation ordering is satisfied. CAPD has been experimentally observed in epitaxial Cu(In,Ga)Se 2 , MgFe 2 O 4 , and SrTiO 3 :Sn grown on GaAs, [17,18] MgO(001), [25] and SrTiO 3 respectively, and in other types of materials like MgAl 2 O 4 and BeAl 2 O 4 . [26] In the following sections, we first focus on the Cu-poor epi-CIGS sample, to introduce the concepts associated with CAPD and to describe two kinds of crystallographic defects.…”

“…Only a handful of 2D extended defects are reported in epitaxial CH crystals grown on zinc-blende (ZB) III-V substrates, namely, 1) boundaries between orientation domains with c-axis pointing in different directions, [17] which we showed are absent in our samples, [9] and 2) cation antiphase boundaries (CAPBs) [17,18] between CH domains sharing translational symmetries of the cation sublattice. In particular, CAPBs in Cu(In,Ga)Se 2 have been studied theoretically [19] and experimentally [18] and have been shown, by means of cathodoluminescence, to have minimal electrical activity. However, to the best of our knowledge, minimal research has been directly toward the study of CAPD in CIGS sulfides.…”