Critical Size of Temperature-Dependent Band Shift in Colloidal PbSe Quantum Dots
William W. Yu.
The temperature-dependent property of band gap in colloidal PbSe quantum dots has been investigated from both experiment
and theory above room temperature. When the particle size increases, the temperature coefficient evolves from negative values to zero
and then to positive value following the trend to its bulk material value. The calculated critical size of 4.88 nm for the temperature coefficient
dE / dT = 0 is consistent with the experimental result. When the particle size is smaller than the critical size, the temperature coefficient
dE / dT is also dependent on the temperature, which has not been observed before. However, this phenomenon is not obvious at
large particle sizes. The functions of size- and temperature-depended band gap E and temperature coefficient dE / dT are achieved
through theoretical calculation and experimental calibration. Temperature-induced variations of quantum confinement energy and exciton-
phonon coupling are the key factors for the temperature coefficient. The balance between the variations of confined effect and exciton-
phonon coupling causes the critical size of temperature coefficient in colloidal PbSe quantum dots.
Keywords: Temperature coefficient, band gap, critical size, exciton-phonon coupling, PbSe quantum dots
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