Near‐Infrared Light‐Responsive Cu‐Doped Cs2AgBiBr6

Fuxiang Ji,Feng Gao,Jiri Brus,Yuqing Huang,Sabina Abbrent,Weimin M Chen,Sergei I Simak,Feng Wang,Chunyang Yin,Fangyan Xie,Libor Kobera,Irina A Buyanova,Johan Klarbring,Igor A Abrikosov

doi:10.1002/adfm.202005521

Abstract

AbstractLead‐free halide double perovskites (A2BIBIIIX6) with attractive optical and electronic features are considered to be a promising candidate to overcome the toxicity and stability issues of lead halide perovskites (APbX3). However, their poor absorption profiles limit device performance. Here the absorption band edge of Cs2AgBiBr6 double perovskite to the near‐infrared range is significantly broadened by developing doped double perovskites, Cs2(Ag:Cu)BiBr6. The partial replacement of Ag ions by Cu ions in the crystal lattice is confirmed by the X‐ray photoelectron spectroscopy (XPS) and solid‐state nuclear magnetic resonance (ssNMR) measurements. Cu doping barely affects the bandgap of Cs2AgBiBr6; instead it introduces subbandgap states with strong absorption to the near‐infrared range. More interestingly, the near‐infrared absorption can generate band carriers upon excitation, as indicated by the photoconductivity measurement. This work sheds new light on the absorption modulation of halide double perovskites for future efficient optoelectronic devices.

Highlights

Lead-free halide double perovskites (A2BIBIIIX6) with attractive optical and contain toxic lead (Pb) and are inferior to commercial devices in terms of electronic features are considered to be a promising candidate to overcome the stability.[5]
High-quality, large-size Cu-doped Cs2AgBiBr6 single crystals with the octahedral shape are obtained by the hydrothermal method (Figure 1a)
The calculations show (Figure S6, Supporting Information) that the direct effects of Cu+ replacement are small, in particular, the effect on the bandgap is negligible. This is in full agreement with our experimental indications of essentially unchanged bandgap and that the observed near-infrared range (NIR) absorption in the Cu doped samples is due to induced defect states, and not a direct effect of Cu on the electronic structure

Summary

Results and Discussion

High-quality, large-size Cu-doped Cs2AgBiBr6 single crystals with the octahedral shape are obtained by the hydrothermal method (Figure 1a). We further perform the time-resolved photoluminescence (TRPL) for all samples at room temperature, and Cs2(Ag:Cu) BiBr6 single crystals show shorter PL lifetime than pristine Cs2AgBiBr6 (Figure S5, Supporting Information) These results imply that the bandgap of Cs2AgBiBr6 is hardly changed; instead, defect states are introduced after Cu doping. The calculations show (Figure S6, Supporting Information) that the direct effects of Cu+ replacement are small, in particular, the effect on the bandgap is negligible This is in full agreement with our experimental indications of essentially unchanged bandgap and that the observed NIR absorption in the Cu doped samples is due to induced defect states, and not a direct effect of Cu on the electronic structure. In Si at the doping concentration of 7 × 1017 cm−3, the high density deep level defects forms an additional band inside the bandgap, which has the implementation for the application as intermediate band solar cell.[28,29] The prominent subbandgap absorption and photoconductivity suggests a great potential for using such devices for near-infrared light detection

Conclusion

Experimental Section

Conflict of Interest