T3.6 Transient Lattice Response Upon Photoexcitation in CuInSe2 Nanocrystals
Samantha Harvey (Northwestern University)
CuInSe2 nanocrystals (CISe NCs) offer promise for optoelectronics such as thin film photovoltaics and printed circuits owing to near-infrared bandgap, low toxicity, and scalable synthesis. Additive manufacturing methods such as photonic curing to produce sintering of NCs offers routes to improved performance, yet little is known regarding the physical behavior of NCs under elevated excitation conditions. Here, we directly investigate the impact of photoexcitation on NC lattice response via time-resolved X-ray diffraction measurements for three sizes of CISe NCs and two different capping ligands (oleylamine and inorganic Na2S) to characterize resultant crystal lattice temperature, phase stability, and thermal dissipation rates. Fluence-dependent measurements show a clear increase in loss of crystallinity with NC size. Kinetics convey a size-dependent recrystallization and cooling lifetime ranging from 80 – 1200 ps and an additional slower cooling lifetime between 2 – 25 ns. The Na2S-capped NCs show reduced melting and recrystallization lifetimes compared to the oleylamine capped NCs and cool completely within ~200 ps. Static XRD with temperature elevation permits evaluation of effective lattice temperature with fluence and also show higher thermal expansion and lower melting temperature than the bulk composition.
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SYMPOSIUM T3 – OPTICAL DEVICE AND PHENOMENON
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Samantha Harvey
Location: Technological Institute M128