  Recently lead halide nanocrystals (quantum dots) have been reported with
potential for photovoltaic and optoelectronic applications due to their
excellent luminescent properties. Herein excitonic photoluminescence (PL)
excited by two-photon absorption in perovskite CsPbBr3 quantum dots (QDs) have
been studied across a broad temperature range from 80K to 380K. Two-photon
absorption has been investigated with absorption coefficient up to 0.085 cm/GW
at room temperature. Moreover, the photoluminescence excited by two-photon
absorption shows a linear blue-shift (0.25meV/K) below temperature of ~220K and
turned steady with fluctuation below 1nm (4.4meV) for higher temperature up to
380K. These phenomena are distinctly different from general red-shift of
semiconductor and can be explained by the competition between lattice expansion
and electron-phonon couplling.Our results reveal the strong nonlinear
absorption and temperature-independent chromaticity in a large temperature
range from 220K to 380K in the CsPbX3 QDs, which will offer new opportunities
in nonlinear photonics, light-harvesting and light-emitting devices.
