A-site Modified Hybrid Perovskites: Compositional Engineering and Role of Grain Boundaries on Optoelectronic Properties (ASTRAL)

基于a位阳离子混合物的杂化碘化铅钙钛矿由于其与母体化合物三碘化铅甲基铵相比具有更高的稳定性而引起了人们的极大关注。本项目的目标是围绕溶液处理a位改性杂化烷基铵碘化铅钙钛矿的可成形性、结晶性和晶界工程的基本认识。通过综合合成、加工和计算，将开发出具有最佳晶体尺寸和溶剂化学性质的功能钙钛矿油墨，用于检测器件结构中固态吸收膜的光电性能。为了了解多阳离子杂化钙钛矿结构的协同效应，详细了解不同a位阳离子的作用和位置以及晶体对称性是至关重要的。由于化学和结构的自由度，我们建议系统地改变a位阳离子的取代，主要负责结构参数（公差因子）和光学带隙的调制。该项目的研究任务将主要集中在(i)基于a位改性化学成分（(A1,A2,A3,A4)PbI3）的钙钛矿油墨配方，结合溶液研究，开发受控晶体生长的合成方案，并测试用于精确晶体工程的新溶剂系统（ii）控制表面晶粒生长和晶粒裁剪单一和串联应用方法的边界（旋转涂层和电喷涂）（iii）钙钛矿固态吸收膜的制造，以研究钙钛矿畴大小的输运性质（iv）详细了解钙钛矿材料及其组成，(v)通过DFT计算验证实验数据，证明混合阳离子钙钛矿中a位工程的影响；（vi）制备薄膜太阳能电池器件结构，评估溶剂、沉积技术和加工条件对器件性能和稳定性的影响。通过光或热刺激过程对预装置结构降解的初步研究也将开始。总之，这一跨学科的努力将追求综合的合成-应用-建模方法，以收集具有a位变化的钙钛矿晶体成核行为的新见解和溶剂效应的原位研究，以获得稳定和可加工的油墨。薄膜形成和器件前结构对光学和输运性质的理解，将通过对a位混合系统缺陷化学的DFT计算和晶界输运建模进行验证。

Hybrid lead iodide perovskites based on a mixture of A-site cations have attracted significant attention due to their higher stability when compared to the parent compound methyl ammonium lead triiodide. The objectives of this project center around fundamental understanding of formability, crystallization and grain boundary engineering in solution-processed A-site modified hybrid alkyl ammonium lead iodide perovskites. Through an integrated synthesis, processing and computational effort, functional perovskite inks with optimal crystal size and solvent chemistry will be developed to examine the optoelectronic properties of solid-state absorber films in device structures. In order to understand the synergistic effect of multi-cation hybrid perovskite structures, detailed information on the role and position of the different A-site cations and crystal symmetry is critically important. Owing to the chemical and structural degrees of freedom, we propose to systematically vary the substitution of A-site cations, which are majorly responsible for the structural parameters (tolerance factor) and modulations in optical band gap The research tasks in this project will primarily focus on (i) formulation of perovskite inks based on A-site modified chemical compositions ((A1,A2,A3,A4)PbI3) in conjunction with solution studies to develop synthetic protocols for controlled crystal growth and test new solvent systems for precise crystal engineering (ii) control of on-surface grain growth and tailoring of grain boundaries in single and tandem application methods (spin-coating and electrospraying) (iii) fabrication of perovskite solid-state absorber films to investigate the transport properties as function of the size of perovskite domains (iv) detailed understanding of perovskite materials, their composition, nucleation and layer growth and effects of intergranular and intragranular transport mechanisms in predevice structures (v) demonstrate the impact of A-site engineering in mixed-cation perovskites by validating the experimental data through DFT calculations and (vi) fabricate thin film solar cell device structures and evaluation of the solvent influence, deposition technique and processing conditions on the device performance and stability. Preliminary studies on degradation of pre-device structures through light or heat-stimulated processes will be initiated as well. In summary, this interdisciplinary effort will pursue an integrated synthesis – application – modelling approach to gather new insights in the nucleation behavior of perovskite crystals with A-site variations and in-situ studies on solvent effects to obtain stable and processable inks, film formation and understanding of pre-device structure towards optical and transport properties that will be validated by DFT calculations on defect chemistry of A-site mixed systems and modelling of grain boundary transport.