Print Email Facebook Twitter Evolution and role of vacancy clusters at grain boundaries of ZnO:Al during accelerated degradation of Cu(In, Ga)Se2 solar cells revealed by positron annihilation Title Evolution and role of vacancy clusters at grain boundaries of ZnO:Al during accelerated degradation of Cu(In, Ga)Se2 solar cells revealed by positron annihilation Author Shi, W. (TU Delft RST/Fundamental Aspects of Materials and Energy) Theelen, Mirjam (TNO/Solliance) Illiberi, Andrea (TNO/Solliance) van der Sar, S.J. (TU Delft RST/Medical Physics & Technology) Butterling, M. (TU Delft RST/Fundamental Aspects of Materials and Energy; TU Delft RST/Neutron and Positron Methods in Materials) Schut, H. (TU Delft RST/Neutron and Positron Methods in Materials) Zeman, M. (TU Delft Electrical Sustainable Energy) Brück, E.H. (TU Delft RST/Fundamental Aspects of Materials and Energy) Eijt, S.W.H. (TU Delft RST/Fundamental Aspects of Materials and Energy) Department Electrical Sustainable Energy Date 2018 Abstract Positron annihilation lifetime spectroscopy (PALS) and Doppler broadening positron annihilation spectroscopy (DB-PAS) depth profiling demonstrate pronounced growth of vacancy clusters at the grain boundaries of as-deposited Al-doped ZnO films deposited as transparent conductive oxide (TCO) on Cu(In,Ga)Se2 (CIGS) solar cells upon accelerated degradation at 85∘C/85% relative humidity. Quantitative fractions of positrons trapped either in the vacancy clusters at the grain boundaries or in Zn monovacancies inside the grains of ZnO:Al were obtained by detailed analysis of the PALS data using a positron trapping model. The time and depth dependence of the positron Doppler depth profiles can be accurately described using a planar diffusion model, with an extracted diffusion coefficient of 35nm2/hour characteristic for in-diffusion of molecules such as H2O and CO2 into ZnO:Al TCO films via the grain boundaries, where they react with the ZnO:Al. This leads to increased open volume at the grain boundaries that imposes additional transport barriers and may lead to charge carrier trapping and nonradiative recombination. Simultaneously, a pronounced increase in series resistance and a strong reduction in efficiency of the ZnO:Al capped CIGS solar cells is observed on a remarkably similar timescale. This strongly indicates that these atomic-scale processes of molecular in-diffusion and creation of open volume at the grain boundaries play a key role in the degradation of the solar cells. Subject Solar CellsPositron Annihilation SpectroscopyGrain BoundariesVacanciesThin FilmsDiffusionElectrical propertiesSolid State ChemistryOptoelectronicsPhySH: To reference this document use: http://resolver.tudelft.nl/uuid:fc0175a0-1dea-4823-aade-9a50d9b77bb4 ISSN 2475-9953 Source Physical Review Materials, 2, 1-18 Part of collection Institutional Repository Document type journal article Rights © 2018 W. Shi, Mirjam Theelen, Andrea Illiberi, S.J. van der Sar, M. Butterling, H. Schut, M. Zeman, E.H. Brück, S.W.H. Eijt, More Authors Files PDF 16102018_eijt.pdf 15.91 MB Close viewer /islandora/object/uuid:fc0175a0-1dea-4823-aade-9a50d9b77bb4/datastream/OBJ/view