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We reported the first-principles computational study of the atomic-scale mechanism underlying the properties of C m O n Cl k /[FA,MA]­Pb1+y I3 heterostructures composed of graphene-related materials C m O n Cl k and formamidinium and methylammonium lead halide perovskites [FA,MA]­Pb1+y I3 (denoting [CH­(NH2)2, CH3NH3]­Pb1+y I3) with a Pb-rich surface that accounts for the proportion factor “y” of Pb. By investigating the structural and electronic properties, the charge carrier transfer, and the quantum transport of electrons, we revealed that among those graphene-related materials, chlorinated graphene oxide (Cl-GO) has the greatest positive effect on both the charge transfer and extraction rates and the stability of perovskite-based photovoltaics. In addition, our study shows that there are intermediate bands generated near the interfaces in Cl-GO/[FA,MA]­Pb1+y I3 heterostructures, which extend the light absorption from the visible light region to the infrared region, enhancing the capability of light absorption of perovskite solar cells.

Two-dimensional (2D) layered organic−inorganic halide perovskites have received increasing research attention because their multiple chemical components impart them with tunable photophysical characteristics. In this study, the influence of organic alkyl ammonium chains on the electronic structures and optical properties of hybrid 2D Ruddlesden−Popper (RP) phase layered halide perovskites A′ 2 Cs m−1 Pb m Br 3m+1 (m = 2) were investigated using first-principles calculations, wherein A′ (A′ = C 4 H 9 NH 3 (including n-butylamine (CH 3 (CH 2 ) 3 NH 3 , BA), isobutylamine ((CH 3 ) 2 CHCH 2 NH 3 , iBA)), C 6 H 13 NH 3 , C 8 H 17 NH 3 , C 10 H 21 NH 3 , and C 12 H 25 NH 3 ) denotes the long alkyl ammonium chain, and m represents the number of inorganic perovskite layers between the long organic chains. The tunable anisotropic structures, electronic structures, transition dipole moments (TDM), and optical properties of these layered halide perovskites were computed, and the obtained results indicated that the in-plane structural distortion caused by the variation in the length of the organic chain led to changes in the band gap. The reduced in-plane structural distortion in these perovskites favors the stronger degeneracy between the top PbBr 2 layer and the bottom PbBr 2 layer, and is responsible for the reduced band gap. Moreover, these 2D layered halide perovskites with a large degree of structural distortion in the [PbBr 6 ] 4− octahedra exhibited a small TDM value.

Tandem solar cells based on perovskite have been gaining ever-increasing attention for applications in photovoltaics. Here we stack the wide-bandgap CsPbI3 top subcell with the low-bandgap Kesterite Cu2ZnSnSxSe(4-x) (CZTSSe) bottom...