Enhanced luminescence and energy transfer in Mn2+ doped CsPbCl3-xBrx perovskite nanocrystals

Manganese ion (Mn2+) doped CsPbCl3-xBrx nanocrystals (NCs) with dual emissions have emerged as a promising candidate for white light emitting devices. The luminescence properties of Mn2+ doped CsPbCl3-xBrx NCs were studied by steady-state and time-resolved photoluminescence (PL) spectroscopy at temperature ranging from 80 to 300 K. The Mn2+ doped NCs with varied Br compositions were synthesized by means of Cl-to-Br anion exchange. The obtained doped NCs exhibited a tunable narrow band-edge emission band from 405 to 500 nm with a lengthened PL lifetime and a wide Mn2+ emission band at 600 nm with a shortened PL lifetime as the Br composition increases. It was interestingly found that PL intensity of the Mn2+ emission band was significantly enhanced by replacing Cl ions with Br and reached the maximum value in Mn2+:CsPbCl2.15Br0.85 NCs. Especially at low temperature (80 K), the intensity ratios of Mn2+ emission to band-edge emission increased approximate to 80 times in Mn2+:CsPbCl2.15Br0.85 NCs, compared with Mn2+:CsPbCl3 ones. The temperature-dependent energy-transfer efficiencies of Mn2+:CsPbCl3 and Mn2+:CsPbCl2.15Br0.85 NCs from excitons in NCs to Mn2+ ions were obtained. The PL enhancement of Mn2+ in CsPbCl3-xBrx NCs was attributed to Br composition-dependent exciton energy transfer to Mn2+.