Proceedings of 13th Conference on Hybrid and Organic Photovoltaics (HOPV21)
Publication date: 11th May 2021
The ability to accurately model, understand and predict the behaviour of crystalline defects would constitute a significant step towards improving photovoltaic device efficiencies and semiconductor doping control, accelerating materials discovery and design.1 In this work, we apply state-of-the-art ab initio techniques - hybrid Density Functional Theory (DFT) including spin-orbit coupling - to accurately model the atomistic behaviour of the cadmium vacancy (VCd) in cadmium telluride (CdTe).2 In doing so, we resolve several longstanding discrepancies in the extensive literature on this subject.
CdTe is a champion thin-film absorber for which defects, through facilitation of non-radiative recombination, significantly impact photovoltaic (PV) performance, contributing to a reduction in efficiency from an ideal (Shockley-Queisser) value of 32% to a current record of 22.1%. Despite over 70 years of experimental and theoretical research, many of the relevant defects in CdTe are still not well understood, with the definitive identification of the atomistic origins of experimentally-observed defect levels remaining elusive.
In this work, through identification of a tellurium dimer ground-state structure for the neutral Cd vacancy, we obtain a single negative-U defect level for VCd at 0.35 eV above the VBM, finally reconciling theoretical predictions with experimental observations. Moreover, we reproduce the polaronic, optical and magnetic behaviour of VCd-1 in excellent agreement with previous Electron Paramagnetic Resonance (EPR) characterisation.
The origins of previous discrepancies between theory and experiment, namely incomplete mapping of the defect potential energy surface (PES) and inherent qualitative errors in lower levels of electronic structure theory, are analysed in detail. Accordingly, this work helps to establish robust procedures for accurate and reliable modelling of defect processes in emerging materials, informing future investigations and enabling the acceleration of materials discovery and design procedures.
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International Conference on Hybrid and Organic Photovoltaics
International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.
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The main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.
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