The Influence of Spontaneous Oxidative Conversion on the Characteristics of Lead‐Free Halide Perovskite CsSn(I_xBr_1−x)₃ and on the Performance of Perovskite Light‐Emitting Diodes

Abstract

In this study, lead‐free perovskite CsSn(IxBr1−x)3 films with photoluminescence emission wavelengths from 677 to 887 nm are prepared. The influence of air exposure on their characteristics is also investigated. It is found that CsSnI3 can be transformed to Cs2SnI6 upon increasing the air exposure time. The decomposition and oxidation mechanisms are confirmed by the X‐ray diffraction pattern due to the presence of CsI peak. It is observed that devices based on the CsSn(IxBr1−x)3 film with increased Br− ratio and the CsSnI3 film with prolonged air exposure time show inferior performance. These results are mainly attributed to the highest occupied molecular orbital levels of CsSn(IxBr1−x)3 and Cs2SnI6. Defect density of state and binding energy of these materials are also investigated and reported in this study.

Pb-free halide perovskites for solar cells, light-emitting diodes, and photocatalysts

“…Interestingly, by exposing the single ABX 3 perovskite CsSnI 3 to air, it can transform to the vacancy ordered Cs 2 SnI 6 state by the oxidation of Sn 2+ to Sn 4+ . 54 Compared to the conventional ABX 3 , A 2 BX 6 compounds typically possess longer B-X bonds, lower defect density, and better stability under ambient conditions. Despite being made by structurally isolated BX 6 octahedra, therefore, exhibiting low structural and electronic dimensionality, some of the materials have surprisingly dispersive electronic bands and low electronic bandgaps.…”

Environment‐Friendly Perovskite Light‐Emitting Diodes: Progress and Perspective

“…In addition, devices based on CsSnI 3 film with longer air exposure time also showed the poor performance with the transforming from CsSnI 3 to Cs 2 SnI 6 , indicating that Sn 2+ were oxidized to Sn 4+ (Figure 4a). [80] Aside from Hong and co-workers first reported PeLEDs made from all-inorganic Sn-based perovskite materials, organic-inorganic hybrid perovskite materials based on Sn were also investigated almost at the same time. Lai et al demonstrated tunable NIR PeLEDs based on CH 3 NH 3 SnI 3 .…”

“…With an inverted LED structure of ZnO nanocrystal/polyethylenimine (PEI) bilayer as an electron-transporting layer (ETL), a (OAm) 2 SnBr 4 2D perovskite film as an emitting layer, 4,4,4″-tris(carbazol-9-yl) triphenylamine (TCTA) as a hole-transporting layer (HTL), and MoO 3 /Au as an anode, the devices based on (OAm) 2 SnBr 4 2D perovskite obtained a low turn-on voltage of 2.2 V, a maximum luminance of 350 cd m −2 and a maximum EQE of 0.1%. [56] By further investigating the main problems of the 2D Sn-based [80] Copyright 2021, Wiley-VCH. b) General crystal schematic of a (PEA) 2 SnI x Br 4−x perovskite (light gray balls: NH 3+ groups; red polyhedra: corner-sharing SnX 6 4− octahedra, where X represents a halide) with alternating organic-inorganic layers.…”

“…Figure 4. a) EL spectra of the light-emitting diodes based on CsSnI 3 films exposed to air for various times. Reproduced with permission [80]. Copyright 2021, Wiley-VCH.…”

Negligible Ion Migration in Tin‐Based and Tin‐Doped Perovskites

“…This is likely due to the higher hole injection barrier and/or trap densities for high bromide ratio compositions in the Sn-based PeLEDs. [27] We further measured the EL spectra and operation stability for Pb-and Sn-based PeLEDs. Figure 4D shows the EL spectra of the PeLEDs under an applied voltage of 4 V at different time intervals.…”