Lead-free halide double perovskites (HDPs) are expected to be promising photovoltaic (PV) materials beyond organic-inorganic halide perovskite, which is hindered by its structural instability and toxicity. The defect- and stability-related properties of HDPs are critical for the use of HDPs as important PV absorbers, yet their reliability is still unclear. Taking CsAgInBr as a representative, we have systemically investigated the defect properties of HDPs by theoretical calculations. First, we have determined the stable chemical potential regions to grow stoichiometric CsAgInBr without structural decomposition. Second, we reveal that Ag-rich and Br-poor are the ideal chemical potential conditions to grow n-type CsAgInBr with shallow defect levels. Third, we find the conductivity of CsAgInBr can change from good n-type, to poorer n-type, to intrinsic semiconducting depending on the growth conditions. Our studies provided important guidance for experiments to fabricate Pb-free perovskite-based solar cell devices with superior PV performances.
The development of high-performance transparent conductors (TCs) is critical to various technologies from transparent electronics to solar cells. Whereas n-type TCs have been extensively applied in many electronic devices, their p-type counterparts have not been largely commercialized due to the lack of ideal materials. Combining atomic replacement and first-principles calculations, seven stable layered double perovskites are identified, i.e.,
We formulate a rule which establishes a sufficient condition that an amorphous binary alloy will be formed by ion mixing of multilayered samples when the two constituent metals are of different crystalline structure, regardless of their atomic sizes and electronegativities. The rule is supported by the experimental results we have obtained on six selected binary metal systems, as well as by the previous data reported in the literature. The amorphization mechanism is discussed in terms of the competition between two different structures resulting in frustration of the crystallization process.
density (n e ). Therefore, it is highly desired to design alternative dopants in In 2 O 3 that can achieve higher μ e and n e than that of Sn.Generally speaking, an ideal n-type dopant that can maintain high μ e and donate sufficient electrons n e into the CB of In 2 O 3 should have its donor level high inside the CB of the In 2 O 3 (Figure 1b). It is expected that some transition-metal (TM) atoms might be the targeted dopants because the TM d orbitals may have sufficiently higher orbital energies than that of In 5s orbitals and they naturally may have multiple valence-electrons that can be effectively doped to the CB of In 2 O 3 to make it n-type. Moreover, differing from Sn, the orbital hybridization between TM d orbitals and In 5s orbitals is weak under the crystal symmetry of In 2 O 3 . As a result, the band curvature, i.e., m e around the CB minimum (CBM) of In 2 O 3 , could be largely maintained. In real situations, the μ e of materials depends on the relaxation time (τ), the electronic charge (q) and m e in the conduction band by following the relationship: μ e = qτ/m e . Therefore, μ e can be increased by increasing τ or by decreasing m e . Increasing τ requires the decrease of impurity scattering, lattice distortion scattering, acoustic phonon scattering, longitudinal optical phonon scattering, etc. [9][10][11] Decreasing m e requires the increase of CBM band edge dispersion. Since TM doping may reduce m e and impurity scattering (for the same carrier density, the required TM dopant density is less than that of Sn), it is reasonable to expected that μ e could be increased by TM doping.In recent years, there has been growing interests in searching ideal TM dopants for n-type In 2 O 3 . [12][13][14][15][16][17][18][19][20][21][22][23] For example, Mo-doped In 2 O 3 (IMO) has attracted particular attention due to its high miscibility and possibility to reach high n e and μ e . [24][25][26][27] However, it is found that the μ e and n e of IMO films strongly depend on their growth temperatures (GT). For example, when the GT increases from 298 to 723 K, the μ e (n e ) of IMO films can dramatically increase from 10 cm 2 V −1 s −1 (6 × 10 19 cm −3 ) to 119 cm 2 V −1 s −1 (7 × 10 20 cm −3 ). [2,26,[28][29][30][31] Although some firstprinciples calculations have been carried out to understand the electronic properties of IMO, [26,32] this puzzling experimental phenomena of GT-dependent electronic properties has not been explained thus far. It is also not clear whether other TM dopants can give better doping properties than Mo.In this article, based on first-principles hybrid functional (HSE06) calculations, we have systemically investigated the Design of novel n-type transparent conducting oxides beyond Sn-doped In 2 O 3 has stimulated extensive interest in the past decade. One of the approaches can be using transition metals (TMs) as dopants. In this article, using In 2 O 3 as an example, it is shown that TM doping in oxides can be classified into three categories (type-I, II, or III) based on their TM d-orbital ...
All-inorganic perovskites with improved stability are expected to be better candidates for optoelectronics, compared to organic–inorganic hybrid perovskites. A new member of all-inorganic perovskites, CsPb2Br5, has attracted great attention for its promising applications in optoelectronic devices. However, the origins of the green emission in CsPb2Br5 have been actively debated. By using first-principles calculations, we find that CsPb and VBr are dominant intrinsic defects independent of the growth conditions within the stable region of CsPb2Br5. Interestingly, we suggest that individual intrinsic defects do not lead to the green emission of CsPb2Br5, while the donor–acceptor pair recombination of CsPb and VBr possibly does. Our findings provide new insights into the experimental controversy about the green emission and its origins in CsPb2Br5 from the perspective of intrinsic defects, which help to extend the application of CsPb2Br5 in optoelectronic devices.
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