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Synthesis and Robotized Screening of Novel Perovskite Materials for Solar Cell Application

Time: Fri 2021-11-26 09.00

Location: F3, Lindstedsvägen 26, Stockholm

Language: English

Subject area: Chemistry

Doctoral student: Allan Starkholm , Tillämpad fysikalisk kemi

Opponent: Professor Kasper Moth-Poulsen, Chalmers University of Technology

Supervisor: Professor Lars Kloo, Tillämpad fysikalisk kemi, Molekylär elektronik, CMD; Professor Per H. Svensson,

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As of today, the energy consumption in the world is high and is essential in the development and growth of the modern-day society. The world energy consumption is projected to increase significantly over the next decades. The energy consumed today is predominantly based on fossil fuels, which is of serious concerns with regards to the environmental impact. Fossil fuels release large amounts of greenhouse gases, such carbon dioxide, upon burning, which in turn contributes to global warming. Moreover, fossil fuel resources are definite and are projected to run out in the near future. Therefore, there is a strong need to consume energy from cleaner, and renewable, sources. Harvesting energy from the sun is one possibility. The sun provides an enormous amount of energy and is a renewable resource. Solar cells convert sunlight to electricity in an emission free manner, which renders them one of the most promising technologies for the future. Silicon solar cells are the most common solar cell technology commercially, with relatively high efficiencies. However, solar cells based on silicon are expensive. Perovskite solar cells (PSCs) have in the last decade emerged as a new and competitive third generation photovoltaic technology with power conversion efficiencies exceeding 25%. Specifically, methylammonium lead triiodide (MAPbI3) represents the archetype of 3D perovskite material that has demonstrated high efficiencies as light-absorbing layers in solar cell devices. Despite the promising properties and the high conversion efficiencies of this class of perovskite materials, there are some important challenges that needs to be addressed prior to large-scale commercialization. The intrinsic instability of the perovskite material towards air, moisture and heat is a serious concern, leading to degradation of the active layer in the solar cell devices in a matter of days. The strict intrinsic size requirements to allow the formation of 3D perovskites limit the number of cations to only a few, which significantly restricts the chemical space for alternative 3D perovskites to be explored. In addition, concerns regarding the toxicity of the standard lead-based perovskites may, because of national legislation, hamper future commercialization. Consequently, there is a need to explore and identify alternative photovoltaic materials with suitable properties. Low-dimensional perovskites offer a vast structural and chemical space to be explored, as well as paving the way for incorporation of functional cations. Low-dimensional perovskite materials typically display relatively large bandgaps and poor charge-transport properties. Therefore, it is necessary to both develop a method to rapidly identify interesting low-dimensional candidate materials, as well as addressing the charge-transport problem. The work presented in this thesis seeks to address these issues.

The aim in this work was to synthesize and characterize novel low-dimensional, perovskite-type materials using two strategies. The first has concerned the utilization of the properties of polyiodides to synthesize new low-dimensional, perovskite-type materials incorporating polyiodide entities linking the low-dimensional framework building blocks. In the second strategy, cationic dyes were used to generate new low-dimensional perovskite compounds internally sensitized with a dye, where the dye acts as cation with respect to the inorganic host structure. In addition, the application of automated robotized screening was explored with the aim to quickly synthesize and identify novel, potentially interesting photovoltaic materials.

In Chapter 1, an introduction to the solar cell field, and especially to the PSCs is presented. In Chapter 2, an overview of the methods used in this work is presented.  

 In Chapter 3, the work using automated robotized screening for the synthesis of new low-dimensional dye-sensitized perovskite-type materials is presented and discussed. The characterization, properties and application of the materials in solar cells are also discussed. 

 In Chapter 4, the work incorporating polyiodides into low-dimensional perovskite-type materials is presented and discussed. Properties of the compounds and their application in solar cells are presented and discussed as well.