A prediction of dislocation-free CdTe/CdS photovoltaic multilayers via nano-patterning and composition grading

• Published in: Progress in photovoltaics Vol. 23; no. 12; pp. 1837 - 1846
• Main Authors: Zhou, Xiao Wang, Ward, Donald K., Doty, F. Patrick, Zimmerman, Jonathan A., Wong, Bryan M., Cruz-Campa, Jose Luis, Nielson, Gregory N., Chavez, Jose Juan, Zubia, David, McClure, John C.
• Format: Journal Article
• Language: English
• Published: Bognor Regis Blackwell Publishing Ltd 01-12-2015; Wiley Subscription Services, Inc; Wiley Blackwell (John Wiley & Sons)
• Subjects: bond order potential; Cadmium sulfides; Cadmium tellurides; CdTe/CdS solar cells; Defects; Dislocations; Grading; molecular dynamics; Multilayers; Nanostructure; Semiconductors
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.2628

Defects in multilayered films have long been a performance‐limiting problem for the semiconductor industry. For instance, CdTe/CdS solar cell efficiencies have had significant improvement in the past 15years or more without addressing the problem of high misfit dislocation densities. Overcoming this stagnation requires a fundamental understanding of interfacial defect formation. Herein, we demonstrate a new first principles‐based CdTe bond‐order approach that enables efficient molecular dynamics to approach the fidelity of density functional theory. Stringent quantum‐mechanical verification and experimental validation tests reveal that our new approach provides an accurate prediction of defects that earlier methods cannot. Using this new capability, we show that misfit dislocations in CdTe/CdS multilayers can be significantly reduced via nano‐patterning and composition grading and more importantly, dislocation‐free multilayers naturally arise when the pattern dimension is reduced below 90nm. Our predictive methods are generally applicable to other materials, highlighting a rational approach towards low‐defect semiconductor films. Copyright © 2015 John Wiley & Sons, Ltd.
A CdTe bond order potential (BOP) developed recently has enabled accurate molecular dynamics (MD) simulations of defect formation in CdTe films. The predicted defects have been validated by high‐resolution microscopy experiments. Using BOP‐based MD simulations, we found that misfit dislocation‐free CdTe/CdS multilayers can be grown by nano‐patterning and composition grading.