Grain-Boundary Phenomena in Halide-Perovskite Thin Films and Solar Cells
Abstract
Organic-inorganic halide perovskites (OIHPs) are a family of materials with unprecedented optical, electronic, and defect-tolerance properties, and they are at the heart of perovskite solar cells (PSCs) — a heavily researched new thin-film photovoltaic (PV) technology. The promise of low-cost, solution-processed PSCs with high efficiencies is driving the PSCs effort worldwide. Grain boundaries (GBs) are ubiquitous in solution-processed and vapor-deposited polycrystalline OIHP thin films used in PSCs. GBs are also known to play an important role in determining certain critical properties and phenomena in OIHPs, which can profoundly influence the performance and stability of the resulting PSCs. While there are many empirical observations of GB effects reported in the literature, a basic understanding of OIHP GBs, and related phenomena, is still lacking. Thus, there is a critical and urgent need for conducting basic materials-science research into this area — a necessary component that will enable PSCs reach their full potential. To address this issue, the overall objective of the proposed research is to gain a deep understanding of GB phenomena in polycrystalline OIHP thin films and related PSCs. A comprehensive, multi-faceted research program is proposed, and it comprises the following three interrelated Tasks, and several Subtasks within: (1) Processing and Characterization, (2) Ionic Diffusion Studies, and (3) Studies of Stability and Performance. The Subtasks within Task (1) Processing and Characterization include: (i) Tailoring of OIHP thin films with a wide range of grain sizes using innovative approaches developed in our laboratory. (ii) Functionalization of OIHP GBs with rationally-designed small molecules, where the ionic diffusion along GBs is retarded, without affecting photocarriers transport. (iii) Fabrication of polycrystalline sintered pellets of OIHPs with a wide range of grain sizes. (iv) Comprehensive microscopic, analytical, spectroscopic, and properties characterization of the resulting materials, including the development of an easy-to-use electrochemical-etching technique for the accurate measurement of grain size. The Subtasks within Task (2) Ionic-Diffusion Studies include: (i) Understand the role of GBs, and the associated space-charge, on the interfacial dynamics in OIHP thin films through electrical measurements. (ii) Elucidate the role of GB functionalization on the ionic diffusion in OIHP thin films. (iii) Perform complementary in situ and operando characterization to understand the interfacial dynamics in OIHP thin films at the atomic/nanometer length scales. (iv) Perform mechanical creep experiments on OIHP polycrystalline pellets as an alternative means for measuring ionic diffusion, complementing the electrical measurements. The Subtasks within Task 3 Studies of Stability and Performance include: (i) Understand the role of GBs on the stability of OIHP thin films under thermal, environmental, electrical, and light stresses. (ii) Elucidate the role of GBs on the stability and performance of PSCs made from these OIHP thin films.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 20, 2020
- Source ID
- N000142012574
Entities
People
- Nitin P Padture
Organizations
- Brown University
- Office of Naval Research
- United States Navy