Co-evaporated hybrid metal-halide perovskite thin-films for optoelectronic applications

Since the fabrication of the first organic-inorganic halide perovskites solar cell in 2009 this material class has shown a lot of promise for solar cell and other semiconductor device applications. The rapid increase in the realised power conversion efficiencies and the unusual properties of the perovskite materials have drawn many researchers to focus on this material group. The perovskite materials which are investigated for use in solar cells, combine many advantageous properties which are known from either organic or inorganic semiconductors. Their high carrier mobilities, long carrier diffusion lengths, and long radiative lifetimes are similar to those in inorganic semiconductors, while the processibility at low temperatures and from solution as well as the chemical tunability of the optical properties are comparable to properties found in organic semiconductors. Co-evaporation is a versatile method to deposit organic-inorganic halide perovskite thin-films. It was pioneered in 2013 and offers several advantages over solution-based deposition techniques. Co-evaporated films are exceptionally smooth and uniform and due to the additive nature of the technique can be deposited onto solvent sensitive substrates which is crucial for the fabrication of flexible substrates or when building a multi-layer stack for tandem solar cells. In this thesis the co-evaporation of organic-inorganic halide perovskite thin-films is developed further and the resulting films and devices are studied in detail. Initially, the first reported co-evaporation of formamidinium lead triiodide (FAPbI3) solar cells is realised and high efficiencies are achieved. Subsequently, the impact of impurities on the co-vaporation of methylammonium lead triiodide (MAPbI3) is studied and insights are gained to improve the process control and reproducibility of the co-evaporation of perovskite thin-films. Finally, the experience and knowledge gained from these two studies are combined to fabricated co-evaporated patterned (FAPbI3) thin-films for applications in semi-transparent solar cells and micro-lasers. The results from this thesis are important contributions towards the deeper understanding of organic-inorganic halide perovskites and their properties as well as towards the development of stable, efficient, large-scale perovskites solar cells.