The toxicity and instability of lead halide perovskite seriously limit its commercial application in lighting, although it has high photoluminescence (PL) efficiency and adjustable emission. Here, lead-free bismuth (Bi) and antimony (Sb) codoped ${\mathrm{Cs}}_2{\mathrm{SnCl}}_6$ (BSCSC) microcrystals (MCs) are prepared successfully by a solvothermal method. The PL spectrum is composed of dual emission bands with the peak at 485 and 650 nm, of which relative intensity can be tunable through the change of Bi and Sb feeding contents, respectively. Because of the phonon–electron interaction, the PL intensity is enhanced as the temperature rises within the range of 80–260 K. Then, the nonradiative transition is intensified until 380 K, which results in decrease in PL intensity. Simultaneously, combining with time-resolved PL, it is concluded that the emission peak at 485 nm is attributed to the [${\mathrm{Bi}}_{\mathrm{Sn}}{\mathrm{V}}_{\mathrm{Cl}}$] as the luminescent centers with the lifetime of hundreds of nanoseconds, and the emission peak at 650 nm is attributed to microsecond-timescale self-trapped excitons. The maximum values of relative sensitivity ($S_R$) and absolute sensitivity ($S_A$) values obtained are $3.82\%{\mathrm{K}}^{-1}$ and $5.11\mathrm{ns}·{\mathrm{K}}^{-1}$, which for the first time to our knowledge demonstrate that BSCSC MCs can be novel luminescent materials for developing better optical thermometry. White-light-emitting diodes (WLEDs) are constructed using BSCSC MCs only combined with an LED chip, the Commission Internationale de L’Eclairage color coordinates of which are (0.30, 0.37). It provides a novel scheme for the lighting field to realize WLEDs without adding additional commercial phosphors.