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Single-crystal SnSe holds the world record for high thermoelectric performance. However, the efficiency of polycrystalline SnSe is limited due to high thermal conductivity (κ) and low electronic conductivity (σ) compared to single-crystal SnSe. Here, we report the low κ and high σ on SnSe with Si doping using semi-classical Boltzmann transport theory and first-principles calculations. Our calculated phonon dispersion curves and elastic constants of the SixSn1−xSe alloys (x varied from 0 to 0.25) show the thermodynamic and mechanical stability. Our density functional theory (DFT)-calculated elastic moduli of the α-SnSe match well with theoretical and experiment reports. The electronic properties are calculated using diversity of exchange-correlation functionals. The band gap for pristine α-SnSe is estimated to be 0.88 eV using the hybrid functional (HSE06), which is in excellent agreement with the experimental value 0.86 eV. The G0W0+Bethe–Salpeter Equation, which incorporates combined electron–electron (e–e) and electron–hole (e–h) interactions, is used to calculate the optical characteristics of pure and Si-alloyed α-SnSe. Our DFT-calculated Seebeck coefficient for SixSn1−xSe alloys for all Si doping concentrations revealed p-type behavior. At 770 K, for x = 0.25, SixSn1−xSe is found to have the lowest thermal conductivity of ~ 0.16 Wm - 1 K - 1 attributed to the high lattice anharmonicity. Our results propose a novel strategy to enhance the optical and thermoelectric properties in the SnSe-based thermoelectric materials. [ABSTRACT FROM AUTHOR]

Summary: 2D Ruddlesden‐Popper (RP) perovskites (R‐NH3)2An−1BnX3n+1 with tailorable photovoltaic features of low toxicity, reduced dimensionality, and defect tolerance hold promise to overcome the main constraints of perovskite solar cells (PSCs). A systematic investigation of the structural and electronic properties of pure and mixed (R‐NH3)2Pb1−xGexI4 systems was performed with and without spin‐orbit coupling (SOC), by using density functional theory (DFT). The organic spacer cations (R‐NH3+)2 of methylammonium (MA‐CH3NH3+) and Phenylethyl ammonium (PEA‐C6H5[CH2]2NH3+) with x = 0.0, 0.25, 0.50, 0.75, 1.0, resulted in the compositionally modified 32‐permutations by systematically substituting the inorganic cations. Short‐range ordering has categorized all studied compositions of (R‐NH3)2Pb0.50Ge0.50I4 into column and battenberg schemes depending on the Ge defect site. The competing effects of octahedral tilting and lattice distortion with bandgap bowing and SOC, across Pb‐Ge compositional systems, provide a systematic strategy to tune bandgaps. By controlling the cations' composition, these mixed 2D‐perovskites outlined the strategy to achieve the desired bandgap and band positions. A rational design approach of low dimensional perovskites was adopted to tune the electronic properties through the spacer and inorganic cation engineering. Our findings expose the scope of monolayer‐based systems as an ideal choice of absorber for the bottom sub‐cell in all‐perovskites 2D‐3D tandem solar cell, harvesting light from visible (2.4 eV) up to infrared (1.2 eV) in the solar spectrum with features of defect tolerance, quantum and dielectric confinement, low bandgap, low effective masses, and high mobility. [ABSTRACT FROM AUTHOR]

Summary: We present a comparative study on the structural, electronic, elastic, and thermoelectric properties of the cubic inverse‐perovskites A3OX (where A = Li, Na, K and X = Cl, Br, I) by density functional theory (DFT). The cohesive, formation, and elastic properties analysis indicates that all studied materials are chemically, thermodynamically, and mechanically stable. Electronic properties reveal that all the inverse A3OX perovskite are direct bandgap semiconductors except Li3OCl and Li3OBr with ionic nature which is confirmed by electron localization function (ELF) analysis. We have also calculated Debye temperature (ΘD) and Grüneisen parameter (γ) to determine the lattice thermal conductivity for all the A3OX materials. Furthermore, thermoelectric (TE) properties are explored by calculating the Seebeck coefficient (S), electronic thermal conductivity, power factor (PF), electrical conductivity (σ/τ), lattice thermal conductivity, and ZT value. Our investigated A3OX inverse‐perovskites provide a fertile base that can improve the overall TE performance for TE applications and green energy production. [ABSTRACT FROM AUTHOR]

Attempts have been made to explore the electronic properties and photovoltaic functionality of Zn-doped orthorhombic CH3NH3PbI3 using the generalized gradient approximation method with van der Waals correction (GGA+vdW). Results show that Zn doping effectively decreases the band gap of orthorhombic CH3NH3PbI3, extending the optical absorption into the near-infrared region of solar irradiance. Simultaneously, the incorporation of Zn substantially increases the electron mobility of CH3NH3PbI3, which is expected to assist the dissociation of electron–hole pairs to effectively reduce the probability for their recombination, leading to improved optical absorption. The combined effects of Zn doping on band gap and carrier mobility significantly enhance the photovoltaic functionality of orthorhombic CH3NH3PbI3. The detailed calculation of formation energy for Zn substitution reveals a high favourability to form such doping in orthorhombic CH3NH3PbI3. The outcome of this work offers great promise for widening practical applications of CH3NH3PbI3 for photovoltaic materials or devices. [ABSTRACT FROM AUTHOR]