Department of Mechanical Engineering, Iowa State University, Ames, IA, USA.
Nanoscale. 2017 Jun 29;9(25):8600-8607. doi: 10.1039/c7nr00459a.
Organic/inorganic lead and tin halide perovskites (CHNHPbI and CHNHSnI) have been promising for photovoltaics because of their high charge carrier mobility, and large absorption coefficient and diffusion length. Both these perovskites also have a notable Seebeck coefficient, depending on the doping level, indicating their potential as thermoelectrics. We create superlattices of these hybrid organic-inorganic halide perovskites and investigate electronic transport through them using first principles computations and experiments. While the transverse components of electrical and electronic thermal conductivities for the superlattices are higher than those for simple perovskite lattices, their longitudinal counterparts are 10 times smaller resulting in overall lower transport coefficients. The superlattice structures have more carriers, but with less average energy compared to pure perovskites causing a lower Seebeck coefficient. However, with the impedance to thermal conduction being relatively stronger than that to charge transfer, the electronic thermoelectric figure of merit of superlattices is higher. Our results lead towards a unique opportunity to engineer the band gap of perovskites by nanostructuring for thermoelectric and optoelectronic applications.
有机/无机铅和锡卤化物钙钛矿（CHNHPbI 和 CHNHSnI）因其载流子迁移率高、吸收系数大和扩散长度大而在光伏领域具有广阔的应用前景。这两种钙钛矿材料的塞贝克系数也很显著，具体取决于掺杂水平，这表明它们有作为热电材料的潜力。我们通过第一性原理计算和实验，制备了这些杂化有机-无机卤化物钙钛矿的超晶格，并研究了它们的电子输运性质。虽然超晶格的横向电导率和电子热导率比简单钙钛矿晶格的高，但它们的纵向对应值小 10 倍，导致整体输运系数较低。超晶格结构具有更多的载流子，但与纯钙钛矿相比，平均能量较低，导致塞贝克系数降低。然而，由于热导的阻抗相对比电荷转移的阻抗更强，因此超晶格的电子热电优值更高。我们的研究结果为通过纳米结构工程来调节钙钛矿的能带结构，从而实现热电和光电应用提供了独特的机会。
