Relaxor Solar Cell Absorbers

Relaxor 太阳能电池吸收器

• 批准号: 406710712
• 负责人: Professor Dr. Doru Constantin Lupascu
• 金额: --
• 依托单位: Institut für Materialwissenschaft
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/406710712?language=en
• 关键词: Relaxor; Solar; Cell; Absorbers

Solar cell absorbers must fulfill a number of requirements for high performance: Appropriate band-gap, high charge carrier mobility and lifetime, appropriate work function to match charge carrier selective conductive layers, and an appropriate design for light capturing. In order to avoid charge carrier recombination, classical semiconductors necessitate exclusive crystal purification techniques removing point and extended defects to very low concentrations. Recently, we showed that the outstanding performance of the new halide perovskite absorbers is partly due to dielectric screening effects. The competition between classical phonon based polaron formation and dipolar dielectric screening permits charge carriers (electrons as well as holes) to propagate very long distances in the crystal without formation of small polarons (states deep in the band-gap) and negligible interaction with existing point defects (vacancies or foreign atoms). This proposal deals with the transfer of this result to those oxide perovskites, in which also two independent polar mechanisms arise, namely relaxor ferroelectrics. Polar nanoregions (PNRs) as well as the classical Fröhlich polaron screening provide independent screening mechanisms. We assume that a similar performance as in the halides can be achieved at much improved lifetime and robustness of the material. The project aims at tuning the band gap of existing relaxor systems towards the optimum for the solar spectrum (around 1.3 eV). The promising candidate relaxor system PbFe0.5Nb0.5O3 (PFN) possesses a band gap of around 1.0 eV. The chemical versatility of the perovskites will allow us to tailor the bandgap and the work function by cation doping. This facile material design will enable the development of a (graded) heterojunction solar cell containing a PFN layer and adjacent layers of doped PFN with properly aligned energy levels, thus obtaining cells with efficient photon capture as well as charge extraction. Efforts of thin film and cell engineering will be continually accompanied by investigation of band structures, structural properties, and charge carrier dynamics. Thus, on the one hand we will achieve new technical developments in the field of heterojunction solar cells and on the other hand we will gain and provide new insights into relaxor based photovoltaics of interest for a broad community in solid state physics.The teams have experience in investigation of the photovoltaic effect in perovskite materials and fabrication of solar cells. They also have a strong background in the study of ferroelectrics and relaxors. A close collaboration between the teams has been established in the last 5 years offering a multitude of complementary expertise necessary for the success of the project: nanoparticle synthesis, thin films preparation, solar cell development, structural characterization, measurements of functional properties on the macroscopic and local scales, dielectric and Raman spectroscopy.

太阳能电池吸收器必须满足高性能的许多要求：适当的带隙，高电荷载流子迁移率和寿命，适当的功函数以匹配电荷载流子选择性导电层，以及适当的光捕获设计。为了避免电荷载流子复合，经典半导体需要专用的晶体纯化技术，将点缺陷和扩展缺陷去除到非常低的浓度。最近，我们发现，新型卤化物钙钛矿吸收剂的出色性能部分是由于介电屏蔽效应。基于经典声子的极化子形成和偶极介电屏蔽之间的竞争允许电荷载流子（电子以及空穴）在晶体中传播非常长的距离，而不形成小的极化子（带隙深处的状态），并且与现有的点缺陷（空位或外来原子）的相互作用可以忽略不计。该提议涉及将该结果转移到那些氧化物钙钛矿，其中也出现两个独立的极性机制，即弛豫铁电体。极性纳米区（PNR）以及经典的弗罗里希极化子筛选提供了独立的筛选机制。我们假设可以在材料的寿命和鲁棒性大大提高的情况下实现与卤化物类似的性能。该项目旨在调整现有弛豫系统的带隙，使其达到太阳光谱的最佳值（约1.3 eV）。有前途的候选弛豫系统PbFe0.5Nb0.5O3（PFN）具有约1.0 eV的带隙。钙钛矿的化学多功能性将允许我们通过阳离子掺杂来定制带隙和功函数。这种简单的材料设计将使得能够开发包含PFN层和具有适当对准的能级的掺杂PFN的相邻层的（分级）异质结太阳能电池，从而获得具有有效光子捕获以及电荷提取的电池。薄膜和电池工程的努力将不断伴随着能带结构，结构特性和电荷载流子动力学的研究。因此，一方面，我们将在异质结太阳能电池领域取得新的技术进展，另一方面，我们将为固态物理领域的广泛社区获得并提供对弛豫基光生伏打的新见解。团队在钙钛矿材料的光伏效应和太阳能电池制造方面具有研究经验。他们在铁电体和弛豫体的研究方面也有很强的背景。在过去的5年中，团队之间建立了密切的合作关系，为项目的成功提供了大量必要的互补专业知识：纳米颗粒合成，薄膜制备，太阳能电池开发，结构表征，宏观和局部尺度上的功能特性测量，介电和拉曼光谱。