Mechanically stable with highly absorptive formamidinium lead halide perovskites [(HC(NH2)2PbX3; X = Br, Cl]: Recent advances and perspectives

Abstract Full potential‐linear augmented plane wave method with two exchange‐correlation potentials Perdew–Burke–Ernzerhof‐generalized gradient approximation and Becke–Johnson have been used to investigate structural, electronic, optical, transport and mechanical anisotropy of formamidinium lead halides (FAPbX 3 ; X = Br, Cl). This computational exploration shows that these materials have a direct band gap, high absorption coefficients and the stability of the compound has been tested using the enthalpy of formation, and elastic stability criteria of the elastic constants. The persistent hybridization of s states of Pb and p states of Br/Cl in valence band contribute significantly in the structural stability. The calculated band gap is 2.26/2.84 eV for FAPbBr 3 /FAPbCl 3 and are in concurrence with the experimental and other theoretical studies. As higher absorption promotes higher emissions, optical properties with the peaks of dielectric function spectra with high energy region, and higher absorption peaks show the significant future for these materials to be used in color light‐emitting diode. Parameters of elastic properties like Bulk modulus, Young's modulus, Pugh's ratio and Poisson's ratio show that these have ductile nature and may be deposited as thin films, which is a significant feature in photovoltaic applications. Moreover, electronic transport properties have been calculated within the constant relaxation time approximation. This provided following observations: (a) Seebeck coefficient are noted to decrease with increasing temperature, (b) electrical conductivity are nearly constant within the whole temperature range, (c) thermal conductivity increased with increasing temperature, and (d) power factor and figure of merits are increasing with increasing temperature, and at a given electron and hole concentration (10 18 –10 19 cm −3 ). The figure of merit signifies that these materials may also be used as thermoelectric devices. These computational observations hereby are of paramount importance for future integrated applications.