**5.2 Cesium lead bromide quantum dot <sup>3</sup> (CsPbBr -QD)**

Quantum dots (QDs) are semiconductor nanoparticles, which can be used to generate high-quality solid-state lighting. QDs are separated into three types: cadmium(Cd)-based QDs, Cd-free QDs, and perovskite QDs. Perovskite quantum dots have shown great potential in nanotechnology and optoelectronic applications. They have been widely studied for successful next-generation optoelectronic applications because of their high PLQY and short PL lifetime [25]. The general chemical formula of perovskite quantum dot is APbX3, where A could be an organic cation such as methylammonium (CH NH 3 3 +, MA) or inorganic cation such as cesium (Cs+) and rubidium (Rb+), Pb represents the lead, and X represents different halide, such as Chloride (Cl), bromide (Br), or iodide (I). Inorganic lead halide perovskites have been attracted enormous scientific attention because of their outstanding optoelectronic properties. They have tunable emission wavelength, high quantum yield, fast radiative response, and a short PL lifetime. These characteristics make them highly attractive for wide range next-generation optoelectronic applications such as LED [26, 27], LD [28, 29], solar cells [30], photodetector [31], and wide gamut display [32]. The cubic crystal structure and photoluminescence emission spectra of APbX3 are shown in **Figure 6(a)** and **(b)**, respectively.

The PL decay lifetime of CsPbBr3 -QD is approximately 7.0 ± 0.3 ns, as shown in **Figure 7(a)**. The absorption and emission spectra of CsPbBr3 -QD is shown in **Figure 7(b)**. CsPbBr3 -QD exhibits an emission peak at 510 nm with narrow full width at half-maximum (FWHM) of 22 nm. CsPbBr3 -QD exhibits high (PLQY>70%), narrow full width half maximum (FWHM = 22 nm) [34, 36–39], relatively short PL lifetime (7 ns) [32], and a modulation bandwidth of 491 MHz [34], *Blue Laser Diode-Based Visible Light Communication and Solid-State Lighting DOI: http://dx.doi.org/10.5772/intechopen.100106*

**Figure 6.**

*(a) The cubic crystal structure of APbX3 [33]. (b) Photoluminescence emission spectra of APbX3 [33].*

**Figure 7.**

*(a) Photoluminescence decay of* CsPbBr3 *-QD monitored at 515 nm [34]. (b) The absorption and emission spectra of* CsPbBr3 *-QD [35].*

which is significantly greater than those of organic materials (40–200 MHz). Therefore, CsPbBr3 -QD is considered a promising substitute for VLC and SSL.
