Employing Low-Cost Organic and Inorganic Hole Transporting Materials for Perovskite Solar Cells

Abstract

Organic-inorganic halide perovskites have attracted substantial attention from the photovoltaic research community since 2009, with power conversion efficiencies (PCE) already exceeding 26.1% 2023. The low cost of perovskite precursors and their simple solution processability make them very promising to be developed as a next-generation photovoltaic technology. However, perovskites are notoriously unstable, particularly in high-humidity environments, which are currently slowing down their widespread implementation. While efficient encapsulation of the full device will certainly inhibit this type of degradation, it is still desirable to fabricate devices which are stable in standard atmospheric conditions. Here, the hole-transporting materials (HTM) play a key role as they can enhance the stability of Perovskite solar cells (PSCs) by acting as moisture barriers. This thesis will discuss the effect of novel hole-transporting materials on Perovskite device performance. Chapter 1 shows the introduction and the aims of this thesis. Chapter 2 gives a general background, the working principle of perovskite solar cells, and introduces the hole transporting materials and their classification as organic and inorganic. Chapter 3 describes the techniques used in the characterization in detail. Chapter 4 represents a new HTM (TPABT) based on familiar building blocks linked by functional amides and their application in PSCs. For a non-conjugated material, this HTM demonstrates the exceptional properties of high conductivity and charge carrier mobility and a blue-shifted onset of absorption that avoids competition for light with the perovskite layer. These observations show that conjugation through the main chain is unimportant for materials with good charge transfer properties. Chapter 5 focused on investigating two new hole transport oxides, CuBi2O4 and NiMnO4, using a novel synthesis method with different variables, such as various salts and hydrothermal treatment of different durations. The XRD patterns of these materials confirmed their crystal structure and alignment with existing databases. Moreover, a perovskite solar cell utilising a spin-coated smooth film of CuBi2O4 as the hole-transporting material achieved an efficiency of 2.13%. Last chapter is the sixth and presents the conclusions and outlook.