Strain-induced bandgap engineering in CsGeX₃ (X = I, Br or Cl) perovskites: insights from first-principles calculations

Abstract

Based on the density functional theory and following the first-principle method, this paper investigated the electronic structures, density of states, effective masses of the electrons and holes, and optical properties...

Electronic and Optical Properties of CsGeX3 (X= Cl, Br, and I) Compounds

“…The exciton binding is defined as the difference between the fundamental band gap and the optical gap after taking the Coulomb interaction into account; furthermore, the binding energy is also strongly proportional/inversely proportional to the effective mass of the carriers/dielectric screening constants. According to the delicate analysis, the typical exciton binding energy of CsGeX 3 lies in the following order: Cl > Br > I atom (Table and Figure g–i); this trend agrees well with the effective mass model. , It is very important to note that the electron–hole interactions in CsGeI 3 are relatively weak and comparable with those in the CsPbI 3 solar cell; the meta-stable exciton states easily break down to create free electron and hole carriers and thus efficiently generate the electrical currents.…”

“…According to the delicate analysis, the typical exciton binding energy of CsGeX 3 lies in the following order: Cl > Br > I atom ( Table 3 and Figure 5 g–i); this trend agrees well with the effective mass model. 33 , 56 It is very important to note that the electron–hole interactions in CsGeI 3 are relatively weak and comparable with those in the CsPbI 3 solar cell; 55 the meta-stable exciton states easily break down to create free electron and hole carriers and thus efficiently generate the electrical currents.…”

A Halide‐Based Perovskite CsGeX3 (X = Cl, Br, and I) for Optoelectronic and Piezoelectric Applications

“…[42] This trend of decreasing bandgaps from CsGe (Cl >Br >I) 3 is in good agreement with earlier reports. [35,39,43,44] But the transfer of photons from the valence band to the conduction band in the I-atom-containing com-pounds will be the fastest among each different functionals employed compounds due to their narrow bandgaps. As a result of substituting halogen atoms, the bandgap of the studied semiconductors can be adjusted in practical applications, which is an important property of materials to be employed in optoelectronic devices.…”

Influence of Sr doping on the photoelectronic properties of CsPbX3 (X = Cl, Br, or I): a DFT investigation

“…To clarify the transport properties, the effective mass of electrons (holes) in the CB (VB) before and after Sr doping was also investigated. The effective mass of electrons (holes) around the bottom of the CB (top of the VB) can be calculated using the following formula: 43 where ħ represents the reduced Planck constant, k represents the wave vector along with different directions, and E ( k ) denotes the energy dispersion relation function. Generally, the greater the dispersion at the bottom of the CB (the top of the VB), the smaller the effective mass of the electron (hole), and the more the conducivity to the diffusion of the electron (hole).…”