Atomistic computer modelling of new solar cell materials

研究背景简介金属卤化物钙钛矿在低成本、高性能和可扩展的光伏(PV)设备中的应用引起了极大的兴奋。这些材料具有一般的ABX3结构，其中A是单阳离子(甲铵，MA；甲酰胺，FA；和/或铯，Cs)，B是双阳离子(通常是铅)，X是阴离子(通常是I或I/Br混合物)。与晶硅相比，钙钛矿通过改变化学成分提供了低温可加工性和带隙可调整性。在10年内，钙钛矿型太阳能电池的功率转换效率(PCE)从3%提高到了25%以上，这是前所未有的。然而，存在着严重的稳定性问题，对支撑缺陷、离子传输和界面性质的全面了解是不完整的。这个项目将通过由赛义夫·伊斯拉姆(SI)教授领导的多方面计算方法来解决这类特殊材料的关键挑战，主要目标如下：(I)阐明离子在多种成分(部分A-阳离子取代和混合I/BR)之间迁移的激活能和扩散系数，并与同类最好的钙钛矿(FA，Cs)PbI3进行比较，作为适当的参照系。(Ii)比较和对比界面离子积累如何影响电流传输和器件稳定性。(Iii)阐明A位阳离子掺杂和2D结构如何能够减少离子迁移和表面反应，并为最佳组成制定设计指南，从而实现工业相关性。c)研究方法的新颖性该项目的特别优势将是(I)能够利用一系列密度泛函理论(DFT)和分子动力学(MD)方法(如VASP，LAMMPS程序)，(Ii)有效开发高性能超级计算机(如Archer-2)，以及(Iii)与牛津物理的实验工作保持密切的协同关系。此外，还将新颖地使用新兴的人工智能(AI)和机器学习技术，这些技术为研究新的光伏材料提供了创新能力，有望实现量子力学的准确性和预测能力，同时比传统方法快许多个数量级。对于这类材料建模工作，牛津大学拥有出色的内部计算设施，SI通过HPC材料化学联盟(SI是Co-I)广泛使用国家Archer-2超级计算机。d)与EPSRC的战略和研究领域保持一致本项目属于EPSRC“能源和脱碳”主题和研究领域：“太阳能技术”和“能源应用材料”。因此，该项目与EPSRC的战略目标保持了良好的一致性，表明“新材料的利用”和“支持材料科学在太阳能技术方面的重大进步”。E)任何参与该项目的公司或合作者都将链接到Henry Snaith FRS教授和Laura Herz教授(两人都在牛津物理学院附近)团队中关于钙钛矿型太阳能电池的互补实验研究。此外，还将与牛津光伏公司进行行业互动。牛津光伏公司成立于2010年，是牛津大学的分支机构，旨在将混合光伏发电商业化。该公司已开发出钙钛矿型硅电池的串联效率高达29%，超过了硅的创纪录表现。

2. Summary of the projecta) Brief description of the context of the researchMetal halide perovskites are generating enormous excitement for their use in low-cost, high-performance and scalable photovoltaic (PV) devices. These materials have the general ABX3 structure, where A is a mono-cation (methylammonium, MA; formamidinium, FA; and/or cesium, Cs), B is a di-cation (typically Pb), and X is an anion (typically I or an I/Br mixture). In contrast to crystalline silicon, perovskites offer low-temperature processability and band gap tunability through modifications of the chemical composition. Within 10 years, there has been an unprecedented rise in the power conversion efficiency (PCE) of perovskite solar cells from 3% to over 25%. However, there are significant stability issues and a full understanding of the underpinning defect, ion transport and interfacial properties is incomplete. Hence, we have yet to unlock the full performance potential of these materials.b) Aims and objectivesThis project will address critical challenges of this extraordinary class of material through a multi-faceted computational approach led by Prof Saiful Islam (SI) with the following key objectives: (i) To elucidate the activation energies and diffusion coefficients for ion migration across multiple compositions (partial A-cation substitution vs mixed I/Br) with comparison to the best-in-class perovskite (FA,Cs)PbI3 as an appropriate reference system.(ii) To compare and contrast how ion accumulation at the interfaces influence current transport and device stability. (iii) To elucidate how A-site cation doping and 2D structures can mitigate ion migration and surface reactions, and to formulate design guidelines for optimum compositions, enabling industrial relevance.c) Novelty of the research methodologyParticular strengths of this project will be (i) the ability to harness a range of density functional theory (DFT) and molecular dynamics (MD) methods (e.g. VASP, LAMMPS codes), (ii) the effective exploitation of high-performance supercomputers (e.g. Archer-2), and (iii) the close synergistic relationship with experimental work in Oxford Physics. In addition, there will be the novel use of emerging artificial intelligence (AI) and machine learning techniques which offer innovative capabilities for studying new PV materials, promising quantum-mechanical accuracy and predictive power, whilst being many orders of magnitude faster than conventional methods. For such materials modelling work, Oxford has excellent in-house computational facilities and SI has extensive access to the national Archer-2 supercomputer through the HPC Materials Chemistry Consortium (SI is Co-I).d) Alignment to EPSRC's strategies and research areas This project falls within the EPSRC 'Energy and Decarbonation' theme and the research areas: 'Solar Technology' and 'Materials for Energy Applications'. Hence, this project aligns well with EPSRC strategic objectives indicating the 'utilisation of new materials' and that 'significant advances in solar technology have arisen from underpinning materials sciences'. e) Any companies or collaborators involvedThis project will have links to complementary experimental studies on perovskite solar cells in the groups of Prof Henry Snaith FRS and Prof Laura Herz (both nearby in Oxford Physics). There will also be industry interactions with Oxford-PV, which was founded in 2010 as a spinout from the University of Oxford to commercialise hybrid photovoltaics and have developed a perovskite-on-silicon tandem efficiency of > 29%, exceeding that of the record performance of silicon.