Related Experiment Video
Updated: Jun 8, 2026
09:51
Atom Probe Tomography Studies on the Cu(In,Ga)Se2 Grain Boundaries
Published on: April 22, 2013
Large neutral barrier at grain boundaries in chalcopyrite thin films
Michael Hafemeister1, Susanne Siebentritt, Jürgen Albert
1Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
Physical Review Letters
|September 28, 2010
Summary
Grain boundaries in copper indium gallium selenide solar cells have a significant neutral barrier. This barrier, several hundred meV high, explains their benign behavior and impacts solar cell efficiency.
Area of Science:
- Materials Science
- Solid-State Physics
- Photovoltaics
Background:
- Grain boundaries in polycrystalline Cu(In,Ga)Se2 thin films are critical for solar cell efficiency.
- A previously suggested neutral barrier of ~0.5 eV was not experimentally confirmed, with prior studies showing only ~10 meV barriers.
Purpose of the Study:
- To investigate the electrical behavior of charged and neutral grain boundaries in Cu(In,Ga)Se2.
- To identify the mechanism responsible for the benign behavior of grain boundaries in these solar cells.
Main Methods:
- Detailed electrical characterization of grain boundaries.
- Analysis of charged and neutral barrier heights and widths.
Main Results:
- An additional, narrow neutral barrier of several hundred meV was identified.
- This barrier is tunneled through by majority carriers.
- The identified barrier height sufficiently explains the benign behavior of grain boundaries.
Conclusions:
- The presence of a significant, albeit narrow, neutral grain boundary barrier is crucial for Cu(In,Ga)Se2 solar cell performance.
- Understanding and controlling these barriers can lead to improved solar cell device efficiency.
Related Concept Videos
01:26Imperfections in Crystal Structure: Stoichiometric Point Defects
Schottky defects arise when some lattice points in a crystal, such as those in NaCl, remain unoccupied, creating lattice vacancies without disturbing the overall electrical neutrality of the crystal. This defect is common in ionic crystals where the positive and negative ions are similar in size, as seen in sodium chloride and cesium chloride. The presence of Schottky defects enables the crystal to conduct electricity to a small extent through an ionic mechanism. Electric fields cause nearby...
01:24Metal-Semiconductor Junctions
The contact of metal and semiconductor can lead to the formation of a junction with either Schottky or Ohmic behavior.
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The semiconductor's...
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The semiconductor's...
01:30The Electrical Double Layer
In the region where two bulk phases meet, an intricate electric charge distribution arises due to charge transfer, ion adsorption, molecular orientation, and charge distortion. This complex distribution is commonly referred to as the electrical double layer.When a solid electrode interfaces with ions in an electrolyte solution, the speed of electron transfer dictates the rates of oxidation and reduction. The electrode acquires a charge through the escape of atoms into the solution as cations or...
01:29Imperfections in Crystal Structure: Non-Stoichiometric Defects
Non-stoichiometric defects refer to a type of defect in the crystal structure of a compound where the ratio of its constituent elements deviates from the ideal stoichiometric ratio. There are two main types of non-stoichiometric defects: metal excess defects and metal deficiency defects.Metal excess defects occur when there is a slight surplus of metal ions than what is required by the stoichiometric ratio of the compound. For example, heating a sodium chloride crystal in sodium vapor results...
02:37Metallic Solids
Metallic solids such as crystals of copper, aluminum, and iron are formed by metal atoms. The structure of metallic crystals is often described as a uniform distribution of atomic nuclei within a “sea” of delocalized electrons. The atoms within such a metallic solid are held together by a unique force known as metallic bonding that gives rise to many useful and varied bulk properties.
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability. Many...
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability. Many...