Superlattice deformation in quantum dot films on flexible substrates via uniaxial strain

• Published in: Nanoscale horizons Vol. 8; no. 3; pp. 383 - 395
• Main Authors: Heger, Julian E., Chen, Wei, Zhong, Huaying, Xiao, Tianxiao, Harder, Constantin, Apfelbeck, Fabian A. C., Weinzierl, Alexander F., Boldt, Regine, Schraa, Lucas, Euchler, Eric, Sambale, Anna K., Schneider, Konrad, Schwartzkopf, Matthias, Roth, Stephan V., Müller-Buschbaum, P.
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 27.02.2023
• Subjects: Deformation; Emission; Energy transfer; Optoelectronics; Phase transitions; Photoluminescence; Photovoltaic cells; Quantum dots; Red shift; Solar cells; Strain; Substrates; Superlattices; Unit cell; X-ray scattering
• ISSN: 2055-6756; 2055-6764; 2055-6764
• DOI: 10.1039/D2NH00548D

The superlattice in a quantum dot (QD) film on a flexible substrate deformed by uniaxial strain shows a phase transition in unit cell symmetry. With increasing uniaxial strain, the QD superlattice unit cell changes from tetragonal to cubic to tetragonal phase as measured with in situ grazing-incidence small-angle X-ray scattering (GISAXS). The respective changes in the optoelectronic coupling are probed with photoluminescence (PL) measurements. The PL emission intensity follows the phase transition due to the resulting changing inter-dot distances. The changes in PL intensity accompany a redshift in the emission spectrum, which agrees with the Förster resonance energy transfer (FRET) theory. The results are essential for a fundamental understanding of the impact of strain on the performance of flexible devices based on QD films, such as wearable electronics and next-generation solar cells on flexible substrates.