Interconnection between Trait, Structure, and Composition of Grain Boundaries in Cu(In,Ga)Se2 Thin‐Film Solar Cells

Advanced Functional Materials, vol. 30

Abstract

Abstract Grain boundaries (GBs) are crucial for solar cells incorporating polycrystalline absorbers and particularly for those characterized by small grain sizes (≈2 µm). For example, random GBs in Si solar cells are found to have a detrimental effect on the cell performance being characterized by an increased recombination activity relative to grains. Yet, their role in Cu(In,Ga)Se2 (CIGS) solar cells still remains controversial. The recent electron‐beam‐induced current (EBIC) study shows that 58% of the GBs in CIGS exhibit enhanced electrical properties considered to be benign (for the device performance). Yet, they coexist with 16% detrimental GBs (reduced electrical properties) and 27% neutral ones (no change in electrical property when compared with the bulk). In the present study, these different GBs are investigated by combining EBIC with electron backscattered diffraction and atom probe tomography techniques on identical GBs. For the first time, a successful correlation is shown (for any device) that interconnects the GB characteristics to its composition. Sufficient statistics demonstrate that the collective fluctuations of all elements at GBs determine its trait. In general, benign (detrimental) GBs are characterized by Cu depletion (enrichment) that favored the formation of donor (acceptor) defects.

Authors 3

1. Mohit Raghuwanshi corresponding Aachen I. Physikalisches Institut IA

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen I. Physikalisches Institut IA Sommerfeldstrasse 14 Aachen 52074 Germany

   RWTH Aachen, I. Physikalisches Institut IA, Sommerfeldstrasse 14, Aachen, 52074 Germany

2. Roland Wüerz

   Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg

   Affiliation as printed

   MAT Department Zentrum für Sonnenenergie‐ und Wasserstoff‐Forschung Baden‐Württemberg (ZSW) Meitnerstraße 1 Stuttgart 70563 Germany

3. Oana Cojocaru‐Mirédin corresponding Aachen I. Physikalisches Institut IA

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen I. Physikalisches Institut IA Sommerfeldstrasse 14 Aachen 52074 Germany

   RWTH Aachen, I. Physikalisches Institut IA, Sommerfeldstrasse 14, Aachen, 52074 Germany