Pb alloying enables efficient broadband emission of two dimensional [NH3(CH2)4NH3]CdBr4

Ultrafast Study of Exciton Transfer in Sb(III)-Doped Two-Dimensional [NH3(CH2)4NH3]CdBr4 Perovskite

“…Consistent with previous results, Cd-PVK exhibits an indirect bandgap with a value of ∼2.83 eV (Figure S13). Upon introducing Sb 3+ , a new 5s-related energy levels near the VBM and 5p-related energy levels below the CBM is observed (Figure b), agreeing well with the projected density of states (PDOS) (Figure c) and previous results. , Such type I band alignment enables the efficient ET from Cd-PVK to Sb 3+ .…”

“…In comparison, the exciton dynamics of Pb 2+ -doped Cd-PVK was investigated as a control experiment. With the introduction of Pb 2+ , the PL spectrum of Cd-PVK-1%Pb (Figure S11) shows one sharp peak located at ∼380 nm (singlet exciton emission of Cd-PVK) and a weak broadband emission (STE emission) centered at ∼470 nm, consistent with previous results . As expected, the TA spectrum (Figure e and f) of Cd-PVK-1%Pb shows a XB at 375 nm before t 0 .…”

“…As an ion with a 5s 2 electron pair, the introduction of Sb 3+ usually has a significant effect on the optical properties of hosts without n s 2 metal ions such as Cs 2 SnCl 6 and Cs 2 MInCl 6 (M = Na, K, Ag) perovskites, since the s-electrons of the dopant would create energy levels within the bandgap that tailor the optical absorption and emission properties of the host. , Encouraged by the significant change of emission color observed in Cd-PVK- x %Sb, UV–vis diffuse reflectance spectroscopy and PL spectra of Cd-PVK- x %Sb were measured (Figure a and b). Pure Cd-PVK exhibits a weak and long absorption tail in the range of 300–750 nm with several small peaks including 334, 388, and 466 nm due to its indirect band nature. ,, However, a totally different absorption feature is observed for Cd-PVK- x %Sb, in which a step-like onset (∼450 nm) with a quasi-saturation at ∼383 nm and a new sharp absorption peak at ∼362 nm can be found. Such major changes mainly arise from the doping of Sb 3+ with the 5s 2 electron lone pair that contributes the valence band maximum (VBM) and induces the transformation from indirect (Cd-PVK) to direct band (Cd-PVK- x %Sb), the same as that of Pb 2+ -doped Cd-based perovskites. , The peaks at 321, 362, and 383 nm for doped samples are attributed to the characteristic 5s 2 → 5s 1 p 1 absorption of [SbBr 6 ] 3– , while 297 nm derives from the absorption of the Cd-PVK host according to the PL excitation (PLE) spectrum (Figure c).…”

“…Pure Cd-PVK exhibits a weak and long absorption tail in the range of 300–750 nm with several small peaks including 334, 388, and 466 nm due to its indirect band nature. ,, However, a totally different absorption feature is observed for Cd-PVK- x %Sb, in which a step-like onset (∼450 nm) with a quasi-saturation at ∼383 nm and a new sharp absorption peak at ∼362 nm can be found. Such major changes mainly arise from the doping of Sb 3+ with the 5s 2 electron lone pair that contributes the valence band maximum (VBM) and induces the transformation from indirect (Cd-PVK) to direct band (Cd-PVK- x %Sb), the same as that of Pb 2+ -doped Cd-based perovskites. , The peaks at 321, 362, and 383 nm for doped samples are attributed to the characteristic 5s 2 → 5s 1 p 1 absorption of [SbBr 6 ] 3– , while 297 nm derives from the absorption of the Cd-PVK host according to the PL excitation (PLE) spectrum (Figure c).…”

“…Cd-PVK and Cd-PVK-Sb products were prepared according to our previous work, and the detailed synthetic procedures can be found in Methods. 36 2D Cd-PVK adopts a monoclinic P2 1 / c space group with corner-shared [CdBr 6 ] 4− inorganic layers and butanediammonium organic layers stacking with each other (Figure 1a). The powder X-ray diffraction (XRD) peaks (Figure 1b) of Cd-PVK identical to that of simulated patterns verifies the high purity of Cd-PVK.…”