10
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: not found

      Annihilation of structural defects in chalcogenide absorber films for high-efficiency solar cells

      Read this article at

      ScienceOpenPublisher
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Defects rapidly annihilate near stoichiometric composition.

          In polycrystalline semiconductor absorbers for thin-film solar cells, structural defects may enhance electron–hole recombination and hence lower the resulting energy conversion efficiency. To be able to efficiently design and optimize fabrication processes that result in high-quality materials, knowledge of the nature of structural defects as well as their formation and annihilation during film growth is essential. Here we show that in co-evaporated Cu(In,Ga)Se 2 absorber films the density of defects is strongly influenced by the reaction path and substrate temperature during film growth. A combination of high-resolution electron microscopy, atomic force microscopy, scanning tunneling microscopy, and X-ray diffraction shows that Cu(In,Ga)Se 2 absorber films deposited at low temperature without a Cu-rich stage suffer from a high density of – partially electronically active – planar defects in the {112} planes. Real-time X-ray diffraction reveals that these faults are nearly completely annihilated during an intermediate Cu-rich process stage with [Cu]/([In] + [Ga]) > 1. Moreover, correlations between real-time diffraction and fluorescence analysis during Cu–Se deposition reveal that rapid defect annihilation starts shortly before the start of segregation of excess Cu–Se at the surface of the Cu(In,Ga)Se 2 film. The presented results hence provide direct insights into the dynamics of the film-quality-improving mechanism.

          Related collections

          Most cited references44

          • Record: found
          • Abstract: not found
          • Article: not found

          19·9%-efficient ZnO/CdS/CuInGaSe2solar cell with 81·2% fill factor

            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Potassium-induced surface modification of Cu(In,Ga)Se2 thin films for high-efficiency solar cells

            Thin-film photovoltaic devices based on chalcopyrite Cu(In,Ga)Se2 (CIGS) absorber layers show excellent light-to-power conversion efficiencies exceeding 20%. This high performance level requires a small amount of alkaline metals incorporated into the CIGS layer, naturally provided by soda lime glass substrates used for processing of champion devices. The use of flexible substrates requires distinct incorporation of the alkaline metals, and so far mainly Na was believed to be the most favourable element, whereas other alkaline metals have resulted in significantly inferior device performance. Here we present a new sequential post-deposition treatment of the CIGS layer with sodium and potassium fluoride that enables fabrication of flexible photovoltaic devices with a remarkable conversion efficiency due to modified interface properties and mitigation of optical losses in the CdS buffer layer. The described treatment leads to a significant depletion of Cu and Ga concentrations in the CIGS near-surface region and enables a significant thickness reduction of the CdS buffer layer without the commonly observed losses in photovoltaic parameters. Ion exchange processes, well known in other research areas, are proposed as underlying mechanisms responsible for the changes in chemical composition of the deposited CIGS layer and interface properties of the heterojunction.
              Bookmark
              • Record: found
              • Abstract: not found
              • Book: not found

              Scanning Probe Microscopy and Spectroscopy

                Bookmark

                Author and article information

                Journal
                EESNBY
                Energy & Environmental Science
                Energy Environ. Sci.
                Royal Society of Chemistry (RSC)
                1754-5692
                1754-5706
                2016
                2016
                : 9
                : 5
                : 1818-1827
                Article
                10.1039/C6EE00402D
                800fd17d-734c-4555-96e8-afd0367f615e
                © 2016
                History

                Comments

                Comment on this article