First-principles study of anion diffusion in lead-free halide double perovskites

Abstract

Halide ion diffusion in organolead halide perovskites has raised great concern in recent years and been considered as the reason for the hysteresis of current-voltage curves and degradation of perovskite solar cells. In this work, X-site halide ion diffusion in lead-free double perovskites CsAgBiX (X = Cl, Br), CsAgSbCl and CsAgInCl is investigated by first-principles calculations. The formation energies of X-site vacancies are calculated for these double perovskites, and predicted to be related to the electronic configurations of B-site cations. CsAgInCl is found to have the lowest vacancy formation energy among these double perovskites due to the unfilled s-orbitals of In. Using the climbing-image nudged elastic band method, these double perovskites are found with different barriers for halide ion migrations around Ag- and B-octahedrons due to different migration bottleneck radii and B-X bond characters. In our calculations CsAgBiBr shows the lowest energy barrier for X-site ion migration, which can explain the phenomenon of the huge hysteresis in CsAgBiBr solar cells reported. These results reveal X-site vacancy formation and diffusion properties in these lead-free halide double perovskites, which could be useful theoretical support for their optoelectronic application.

Pressure‐Dependent Mechanical and Thermal Properties of Lead‐Free Halide Double Perovskite Cs2AgB″X6 (B″═In, Bi; X═Cl, Br, I)

“…[14,[17][18][19][20] Compared to Cs 2 AgInX 6 , Cs 2 AgBiX 6 (X═Cl, Br, I) exhibited the lower energy barrier for X-site ion migration although its vacancy formation was larger. [17,21] By contrast, Cs 2 AgInBr 6 has been regarded as the most promising member to substitute the LHP to be as a light absorber layer for the perovskite solar cell (PSC) since the ideal power conversion efficiency (PCE) of Cs 2 AgInBr 6 based PSC was up to 28% which was close to the theoretical PCE of CH 3 NH 3 PbI 3 based PSC (about 30%). [20] Moreover, the open circuit voltage (V oc ) of PSC based on Cs 2 AgBiBr 6 exceeded 1 V which was the highest reported V oc for a bismuth halide perovskite, although the PCE of Cs 2 AgBiBr 6 based PSC was just less than 8%.…”

Potential Substitutes for Replacement of Lead in Perovskite Solar Cells: A Review

“…The double perovskite Cs 2 AgInCl 6 is having lowest vacancy formation energy due to unfilled s‐orbital of In 3+ . The hysteresis loss in Cs 2 AgBiBr 6 solar cells is attributed to the lowest energy barrier for X‐site migration . Double perovskite lead‐free layered Cs 4 CuSb 2 Cl 12 have been reported with a bandgap of 1 eV prepared by grinding of precursor salts at ambient conditions.…”

“…The hysteresis loss in Cs 2 AgBiBr 6 solar cells is attributed to the lowest energy barrier for X-site migration. [319] Double perovskite lead-free layered Cs 4 CuSb 2 Cl 12 have been reported with a bandgap of 1 eV prepared by grinding of precursor salts at ambient conditions. A long range magnetic ordering is displayed by the synthesized perovskite at room temperature that plays a pivotal role in controlling the electronic properties of double perovskite Cs 4 CuSb 2 Cl 16 .…”

First‐Principles Calculations to Investigate the Refractive Index and Optical Dielectric Constant of Na3SbX4 (X = S, Se) Ternary Chalcogenides

“…Solar energy is important to solve the energy and environment crises. [1][2][3][4] In order to enhance the solar cells efficiency, much efforts have been put to explore visible-light harvesting materials. [5][6][7][8][9][10] Metal chalcogenides have attracted much attention in the field of solar energy conversion due to their outstanding optical and electrical properties.…”

“…The solar cell employing the ternary sodium sulfide NaSbS 2 as absorber has achieved an initial power conversion efficiency, 2.3%, suggesting a promising potential in superionic conductors' application. Moreover, ternary sulfide Na 3 SbS 4 has been fabricated as solid-state electrolyte of sodiumions batteries. [16,17] Rush et al [18] have improved the nextgeneration batteries on the basis of Na 3 SbS 4 as an ion conductor with high ionic conductivities in the mS cm À1 range.…”