Theoretical Investigation of the Role of Anion and Trivalent Cation Substitution in the Physical Properties of Lead-Free Zero-Dimensional Perovskites

Abstract

Zero-dimensional (0D) perovskites have received increased attention in the last years due to their wide range of compositions and suitable optoelectronic properties for several technological applications. Here, we performed density functional theory calculations to investigate the role of halide anion (X = Cl, Br, I) and trivalent cation (B = Bi, Sb) substitution in the structural, energetic stability, optoelectronic, and excitonic properties of lead-free 0D perovskites using the C20H20N4B2X10 and C30H25N6BX6·2H2O compounds as prototype structures. We found a crucial role of the replacement of the halide species in the investigated physical properties; that is, most properties change (decrease or increase) almost linearly from Cl → Br → I, while the effects induced by B are less pronounced. For example, 0D perovskites with smaller halide species have higher energetic stability. The valence band is dominated by the X p-states, in which the electron binding decreases from 3p → 4p → 5p, and hence, it yields a reduction of the band gap energy as Cl is replaced by Br and then by I. The electronic band structures are very flat, which can be explained by the 0D nature of the crystal structures (i.e., isolated inorganic octahedra). As expected, spin–orbit coupling is more significant for I-based systems. As a consequence of quantum confinement, the exciton binding energies of 0D perovskites (up to 456.95 meV) are about 2 orders of magnitude higher than their conventional 3D counterparts. Finally, we found power conversion efficiencies to be less than 14% for all systems.

Photovoltaic Efficiency of Transition Metal Dichalcogenides Thin Films by Ab Initio Excited-State Methods

“…Delving into this possibility, and taking into account that the excitonic effects in bulk TMDCs play a key role in their optical responses, we also compute the PCE using a slightly modified SLME approach that has been proposed by Ozório and co-workers . In their model, the fraction of the radiative recombination current, f r , is calculated by replacing the Δ r in eq with Δ X , which is defined as Δ X = X A − X normalg normals We refer to this approach as exciton-based SLME or SLME-X.…”

“…Herein, we employ the ab initio many-body perturbation theory within the GW-BSE scheme to investigate the optoelectronic properties of bulk 2H-TMDCs and then address their theoretical photovoltaic efficiencies. We analyze the powerconversion efficiency of MX 2 TMDCs with M = Mo, W and X = S, Se, modeling the inclusion of non-radiative recombination losses with exciton eigenvalues computed by BSE, in an approach we denote as SLME-X which follows the approach proposed by Ozoŕio and co-workers, 30 and compared those results with another modeling in which we estimate the fraction of radiative recombination processes using reported values obtained by photoluminescence quantum yield experiments (SLME-PLQY). Applying the SLME-X approach, the photovoltaic efficiencies of the TMDCs consistently fell within the range of 23−29%, reaching efficiencies analogous to those obtained using the Shockley−Queisser formalism.…”

Decoding Van der Waals Impact on Chirality Transfer in Perovskite Structures: Density Functional Theory Insights

“…Consequently, changes in chemical composition within the inorganic framework offer a possible route for tuning the band gap in these materials. 72 In Figure 9, we show the electronic band structures for the chiral 0D-R, 1D-R, 2D-R, and 3D-R perovskites. Because the inorganic framework rules the electronic states near the band edges, the structure dimensionality manifested through the interconnectivity of the octahedra plays a crucial role in the properties of electronic bands near the band gap, particularly the curvature of the bands.…”

“…Furthermore, to characterize the magnitude of binding between organic cations and the inorganic framework, the binding energy per atom (E b ) was calculated using the following equation, E b = E coh − (E coh org + E coh inorg ). 72 The results are shown in Figure 6 (top panel). For all systems, E coh presents negative values (as expected by its definition) and the magnitude of E coh increases in the sequence 3D-R, 1D-R/S, 2D-R/S, and 0D-R/S.…”

Chemical etching strategy to prepare microtubes of a hybrid organic cuprous halide

“…36 A convenient synthesis for hybrid organic cuprous chloride and bromine could help to enrich the structures and functions of hybrid organic cuprous halides, including bandgap engineering. 37,38 As mentioned above, it is natural to propose the synthesis of hybrid organic cuprous halide tubes. Then, through infill replacement and fluorescence switching of the tubes, we can develop a wide variety of applications of hybrid organic cuprous halides.…”