Historically, thermoelectric technology has only occupied niche areas, such as the radioisotope thermoelectric generators for NASA's spacecrafts, where the low cooling coefficient of performance (COP) and energy-conversion efficiency are outweighed by the application requirements.Recent materials advances and an increasing awareness of energy and environmental conservation issues have rekindled prospects for automotive and other applications of thermoelectric materials.This article reviews thermoelectric energy-conversion technology for radioisotope space power systems and several proposed applications of thermoelectric waste-heat recovery devices in the automotive industry.

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We adopt a global optimization method to predict two-dimensional (2D) nanostructures through the particle-swarm optimization (PSO) algorithm. By performing PSO simulations, we predict new stable structures of 2D boron-carbon (B-C) compounds for a wide range of boron concentrations. Our calculations show that: (1) All 2D B-C compounds are metallic except for BC(3) which is a magic case where the isolation of carbon six-membered ring by boron atoms results in a semi-conducting behavior. (2) For C-rich B-C compounds, the most stable 2D structures can be viewed as boron doped graphene structures, where boron atoms typically form 1D zigzag chains except for BC(3) in which boron atoms are uniformly distributed. (3) The most stable 2D structure of BC has alternative carbon and boron ribbons with strong in-between B-C bonds, which possesses a high thermal stability above 2000 K. (4) For B-rich 2D B-C compounds, there is a novel planar-tetracoordinate carbon motif with an approximate C(2)(v) symmetry.

The electronic properties of ABX 3 (A = Cs, CH 3 NH 3 , NH 2 CHNH 2 ; B = Sn, Pb; X = Cl, Br, I) type compounds in the cubic phase are systematically studied using the first-principles calculations. We find that these compounds have direct band gaps at R point where the valance band maximum is an anti-bonding state of B s-X p coupling, while the conduction band minimum is a non-bonding state with B p characters. The chemical trend of their properties as A or B or X varies is fully investigated, which is of great importance to understand and optimize this kind of solar cell materials. We find that: (i) as the size of A increases, the band gap of ABX 3 will increase; (ii) as B varies from Sn to Pb, the band gap of ABX 3 will increase; and (iii) as X ranges from Cl to Br to I, the band gap will decrease. We explained these trends by analyzing their band structures. Furthermore, optical properties of the ABX 3 compounds are investigated. Our calculations show that taking into account the spin-orbit coupling effect is crucial for predicting the accurate band gap of these halide perovskites. We predict that CH 3 NH 3 SnBr 3 is a promising material for solar cells absorber with a perfect band gap and good optical absorption.

The emergence of cesium lead iodide (CsPbI3) perovskite solar cells (PSCs) has generated enormous interest in the photovoltaic research community. However, in general they exhibit low power conversion efficiencies (PCEs) because of the existence of defects. A new all‐inorganic perovskite material, CsPbI3:Br:InI3, is prepared by defect engineering of CsPbI3. This new perovskite retains the same bandgap as CsPbI3, while the intrinsic defect concentration is largely suppressed. Moreover, it can be prepared in an extremely high humidity atmosphere and thus a glovebox is not required. By completely eliminating the labile and expensive components in traditional PSCs, the all‐inorganic PSCs based on CsPbI3:Br:InI3 and carbon electrode exhibit PCE and open‐circuit voltage as high as 12.04% and 1.20 V, respectively. More importantly, they demonstrate excellent stability in air for more than two months, while those based on CsPbI3 can survive only a few days in air. The progress reported represents a major leap for all‐inorganic PSCs and paves the way for their further exploration in order to achieve higher performance.