Nature's imperfections can sometimes unlock interesting and sought for properties. A team from IP PAS and MIT has found that structural point defects can serve as the origin of unusual photoluminescence in the visible range. 

Structural sulfur point defects and vacancies have been found to be the origin of unusual photoluminescence in the 2-3 eV range. We have also found that various defect states tune photoluminescence band shape.

Material engineers often strive for perfection in material growth, aiming for flawless composition, shape, and structure. However, nature's imperfections can sometimes unlock unique properties without perfect periodicity and symmetry. In our newly published paper in Advanced Optical Materials, we demonstrate how these imperfections can be harnessed to tune and enhance photoluminescence in AgScP₂S₆ - a new layered semiconductor belonging to the metal thiophosphate (MTP) family of materials that has been recently synthesized in the USA. Experiments conducted at the Institute of Physics in Warsaw and in the USA at MIT show that sulfur vacancies in AgScP₂S₆ facilitate defect-state-to-valence-band transitions, resulting in visible light emission, while structural defects formed naturally during growth can enhance and modulate the photoluminescence intensity and shape its spectrum. These findings show the potential of strain and defect engineering in MTPs for realizing tunable emitters in the visible spectrum.

We thank the MIT International Science and Technology Initiatives (MISTI) program for their Global Seed Funds initiative, which made this collaboration possible.