Excitonic emissions and above-band-gap luminescence in the single-crystal perovskite semiconductorsCsPbBr3andCsPbCl3

The ternary compounds $\mathrm{CsPb}{X}_{3}$ ($X=\mathrm{Br}$ or Cl) have perovskite structures that are being considered for optical and electronic applications such as lasing and gamma-ray detection. An above-band-gap excitonic photoluminescence (PL) band is seen in both $\mathrm{CsPb}{X}_{3}$ compounds. An excitonic emission peak centered at 2.98 eV, $\ensuremath{\sim}0.1$ eV above the room-temperature band gap, is observed for $\mathrm{CsPbC}{\mathrm{l}}_{3}$. The thermal quenching of the ex