Metal Ion-Incorporated Lead-Free Perovskites toward Broadband Photodetectors

Abstract

Metal halide perovskites have excited tremendous research interests due to their extraordinary photovoltaic and optoelectronic performance. Cs2SnI6 has emerged as a promising lead-free perovskite in advanced optoelectronics due to its high stability, appropriate bandgap, and high absorption coefficient. The performance of two-dimensional (2D) Cs2SnI6-based photodetectors is limited as compared to lead-based perovskites. Here, we report a simple strategy for incorporating aliovalent metal ions (nickel and zinc) for doping or passivation of perovskites to improve their performance. Aliovalent metal ions are employed to break the inherent dark transition of the 2D Cs2SnI6, greatly increasing photoluminescence by two orders of magnitude than pristine Cs2SnI6. Density function calculation reveals the n-type doping of nickel ions without introducing any deep trap states. We further demonstrate that the surface passivation of 2D Cs2SnI6 by zinc ions can greatly reduce surface trap/defect density. Aliovalent metal ion-incorporated Cs2SnI6 perovskites exhibit broadband detection, high responsivity (1.6 × 103 A W–1, for Ni-incorporated Cs2SnI6) and high detectivity (1.56 × 1013 Jones, for Zn-incorporated Cs2SnI6). These results will prompt research on the influence of metal ions in perovskite materials that may afford novel properties for next-generation optoelectronics.

Metal Work Function Effects on the Performance of UV–Visible–NIR Cs2SnI6 Photodetectors for Flexible Broadband Application

“…The cesium vacancy (V Cs ) is a deep acceptor located 0.52 eV above the VBM of the CSI devices (Figure 2b,c). [6,15,46] These defects can affect the PDPs of CSI PDs under the illumination of light sources (Figure 2d,e). The extraction of Schottky barrier height (Φ B ) at top metal electrodes/n-type semiconductor (CSI) interface can be predicted by the Schottky-Mott rule [6] Φ…”

“…[3,[6][7][8][9] Among various inorganic perovskite materials (Cs 2 SnI 6 , [6] Cs 3 Bi 2 I 6 Br 3 , [8] Cs 3 Bi 2 I 9 , [10] Cs 3 Sb 2 I 9 , [11] Cs 3 MnBr 5 , [12] CsCu 2 I 3 [13] and others), [3,7,14] Cs 2 SnI 6 (CSI) has attractive features like a high absorption coefficient (%10 4 -10 5 cm À1 ) in broader UV-visible-NIR spectral regime, direct optical bandgap (1.3-1.6 eV), and decent carrier mobility (1-510 cm 2 V À1 s À1 ). [6,15,16] The CSI particlebased films [6,[17][18][19] and direct-solution spincoated CSI films [20][21][22] were adopted as photosensitive layers for broadband UVvisible-NIR PDs applications. [6,15,17,18,20,22] These CSI-based broadband PDs were implemented on various substrates, such as rigid (glass, [6,20] SiO 2 , [15,22] fluorine-doped tin oxide (FTO), [19,21] and indium tin oxide (ITO) [17,18] ) and flexible polyethylene terephthalate (PET) substrates.…”

“…[ 6,15,16 ] The CSI particle–based films [ 6,17–19 ] and direct‐solution spin‐coated CSI films [ 20–22 ] were adopted as photosensitive layers for broadband UV–visible–NIR PDs applications. [ 6,15,17,18,20,22 ] These CSI‐based broadband PDs were implemented on various substrates, such as rigid (glass, [ 6,20 ] SiO 2 , [ 15,22 ] fluorine‐doped tin oxide (FTO), [ 19,21 ] and indium tin oxide (ITO) [ 17,18 ] ) and flexible polyethylene terephthalate (PET) substrates. [ 6 ] The operational stability, such as storage stability [ 6,15,17,21 ] over time at room temperature, and thermal stability [ 6 ] of CSI PDs were systematically studied previously.…”

“…[ 6,15,17,18,20,22 ] These CSI‐based broadband PDs were implemented on various substrates, such as rigid (glass, [ 6,20 ] SiO 2 , [ 15,22 ] fluorine‐doped tin oxide (FTO), [ 19,21 ] and indium tin oxide (ITO) [ 17,18 ] ) and flexible polyethylene terephthalate (PET) substrates. [ 6 ] The operational stability, such as storage stability [ 6,15,17,21 ] over time at room temperature, and thermal stability [ 6 ] of CSI PDs were systematically studied previously. [ 6,15,21 ] The enhancement of photodetection properties (PDPs) for PDs was reported in the literature via metal ion (e.g., Zn, Ni) doping.…”

“…[ 6 ] The operational stability, such as storage stability [ 6,15,17,21 ] over time at room temperature, and thermal stability [ 6 ] of CSI PDs were systematically studied previously. [ 6,15,21 ] The enhancement of photodetection properties (PDPs) for PDs was reported in the literature via metal ion (e.g., Zn, Ni) doping. [ 13 ] However, the literature has not addressed the effect of metal electrode work function on PDPs of flexible CSI PDs.…”