Cs_1−xRb_xSnI₃light harvesting semiconductors for perovskite photovoltaics

Abstract

aWe show that films of the 3-dimensional perovskite Cs 1Àx Rb x SnI 3 can be prepared from room temperature N,N-dimethylformamide solutions of RbI, CsI and SnCl 2 for x r 0.5, and that for x r 0.2 film stability is sufficient for utility as the light harvesting layer in inverted photovoltaic (PV) devices. Electronic absorption and photoluminescence spectroscopy measurements supported by computational simulation, show that increasing x increases the band gap, due to distortion of the lattice of SnI 6 octahedra that occurs when Cs is substituted with Rb, although it also reduces the stability towards decomposition. When Cs 0.8 Rb 0.2 SnI 3 perovskite is incorporated into the model inverted PV device structure; ITO|perovskite|C 60 |bathocuproine|Al, an B120 mV increase in open-circuit is achieved which is shown to correlate with an increase in perovskite ionisation potential. However, for this low Rb loading the increase in band gap is very small (B30 meV) and so a significant increase in open circuit-voltage is achieved without reducing the range of wavelengths over which the perovskite can harvest light. The experimental findings presented are shown to agree well with the predictions of density functional theory (DFT) simulations of the stability and electronic structure, also performed as part of this study.

Efficient and Hole‐Transporting‐Layer‐Free CsPbI2Br Planar Heterojunction Perovskite Solar Cells through Rubidium Passivation

“…After the incorporation of Rb, the Cs 3d 5/2 and Cs 4d 3/2 peaks show a slight shift to lower binding energies compared with the reference film without Rb, which is consistent with the previous reports on Rb‐substituted CsSnI 3 films . Conversely, the Pb 4f 5/2 and Pb 4f 7/2 peaks shift to higher binding energies after Rb doping.…”

Efficient Intraband Hot Carrier Relaxation in the Perovskite Semiconductor Cs1–xRbxSnI3 Mediated by Strong Electron–Phonon Coupling

“…to CB1 in Figure 1 x. 37 The spectrum exhibits the asymmetric shape typical of PL from non-equilibrium carriers in direct-gap semiconductors, with a high-energy tail that has a shallower gradient than the low-energy tail. Under 532 nm excitation (2.33 eV) interband absorption from VB1…”

“…Partial Rb substitution was adopted as it benefits PV performance. 37 In addition to the importance of this material for PV applications, it is also a cleaner model system to study hot carrier cooling effects than the organic-inorganic lead halide perovskites for two reasons. Firstly, the choice of an inorganic A-site cation (Cs/Rb) eliminates possible effects associated with reorientations of the organic cations.…”

Will organic–inorganic hybrid halide lead perovskites be eliminated from optoelectronic applications?

“…However, a further increase in the Rb content (x > 0.5) can easily cause SnI 6 octahedral lattice distortion and strain, which lead to a decrease in stability. 63 The band gap distribution obtained with rst-principles DFT calculations over approximately 260 species of inorganic lead-free perovskites further suggests that cubic-KSnCl 3 and cubic-RbSnCl 3 with ideal band gaps (1.24-1.44 eV) may be potential replacements for Pb-based perovskites. 65 Thus, it is worth exploring the photoelectric properties of both materials in the future.…”