Based on the wide emission characteristics of STEs from Te
4+ and Sb
3+, we further synthesized Cs
2ZnCl
4:Sb
3+,Te
4+ SCs. Compared with Cs
2ZnCl
4:Sb
3+ and Cs
2ZnCl
4:Te
4+ SCs, PL of Cs
2ZnCl
4:Sb
3+,Te
4+ SCs are almost the same, however, PLE of Cs
2ZnCl
4:Sb
3+,Te
4+ SCs come from the superposition of PLE of Cs
2ZnCl
4:Sb
3+ and Cs
2ZnCl
4:Te
4+ SCs (
Figs. 3a and
b). Firstly, we synthesized Sb
3+ doped Cs
2ZnCl
4 SCs with Sb/Zn feeding ratio of 10%, 20%, 30%, 40% and 50% (Fig. S4 in Supporting information). The actual Sb
3+ doping concentrations are shown in Table S1 (Supporting information). It could be seen that with increasing Sb
3+ doping concentration, the emission of Cs
2ZnCl
4:Sb
3+ first increases and then decreases owing to the concentration quenching effect, achieving a maximum of FWHM up to 192 nm when the feeding ratio of Sb/Zn is 30% (Fig. S5a in Supporting information). According to the PL decay curves of Cs
2ZnCl
4:Sb
3+ SCs, the lifetime based on single exponential-fitting is calculated to be 12.61, 12.68, 13.07, 12.84 and 12.10 µs for Cs
2ZnCl
4:10%−50%Sb
3+, respectively (Fig. S5b in Supporting information). In addition, the lifetimes of Cs
2ZnCl
4:Sb
3+ SCs show firstly a slightly monotonic increase and then decrease with increasing Sb
3+ concentration. This is related to the increased non-radiative transition [
42]. From the optimal concentration of Sb
3+ doping, we further doped Te
4+ with different concentrations from 10% to 50% to form Cs
2ZnCl
4:Sb
3+,Te
4+ SCs. From the PL spectra of Cs
2ZnCl
4:Sb
3+,Te
4+ SCs (Fig. S6a in Supporting information), it was found that the emission intensity also increases and then decreases with increasing the feeding ratio, satisfying the concentration quenching effect, and the optimum doping concentration of Te
4+ was determined to be 40%. Time-resolved photoluminescence decay experiments (
Fig. 3c) show that the lifetimes measured at 590 nm are 47.48, 52.49, 52.53, 58.41 and 56.80 ns for 10%−50%Te
4+ co-doped Cs
2ZnCl
4 SCs, respectively, which are comparable to the decay lifetimes of STEs emissions of reported low-dimensional metal halides [
40,
43]. It can be easily seen from
Fig. 3c that under 375 nm excitation, the decay times of the inherent radiation for different Te
4+ concentrations monitored at 590 nm also firstly increase and then decrease slightly with increasing Te
4+ concentration, which is associated with the non-radiative transition [
42]. Furthermore, the lifetimes of Cs
2ZnCl
4:30%Sb
3+,y%Te
4+ monitored at 720 nm have been collected in Fig. S6b (Supporting information) and there is almost no significant change with the change of Te
4+ concentration. As a result, we believe that Cs
2ZnCl
4:30%Sb
3+,40%Te
4+ SCs are the appropriate choice for subsequent discussion of Sb
3+ and Te
4+ co-doped Cs
2ZnCl
4 SCs. From
Fig. 3d, the PL emission band (λ
ex = 365 nm) could be fitted as fit peaks 1 and 2, corresponding to Sb
3+ and Te
4+ emission, respectively, indicating the formation of double broad peaks of emission under the same excitation. Based on previous reports, the origins of PL of Cs
2ZnCl
4:Sb
3+,Te
4+ SCs are illustrated in
Fig. 3e [
44,
45]. Upon different excitations, electrons are first excited from 5s states of Sb
3+ or Te
4+ ions to their 5p states and then trapped in [SbCl
4]
− or [TeCl
4] tetrahedrons, which sequentially induced triplet dopant STEs, respectively. For Te
4+ ions, by considering the contribution of lattice vibration to the transition process and the transition selection law, the high-energy band of PLE could be attributed to the
1S
0 →
3P
2 transition of Te
4+ via spin–orbit coupling, which is a double peak due to the Jahn-Teller effect. And the low-energy band of PLE is attributed to the
1S
0 →
3P
1 transition of Te
4+ [
46]. Besides, the PLQYs of Cs
2ZnCl
4:30%Sb
3+ and Cs
2ZnCl
4:5%Te
4+ are 15.2% and 1.3%, respectively (Fig. S7 in Supporting information), the PLQY of Cs
2ZnCl
4:30%Sb
3+,40%Te
4+ is 0.8% (Fig. S8a in Supporting information). According to
Fig. 2 and Figs. S8b and c (Supporting information),
S of Cs
2ZnCl
4:Sb
3+, Cs
2ZnCl
4:Te
4+ and Cs
2ZnCl
4:30%Sb
3+,40%Te
4+ are determined to be 27.63, 25.84 and 17.13, respectively. It seems to be a correlation between PLQYs and
S.