Design, synthesis and characterization of Dimethylammonium / Ethylammonium / Cesium Lead  Halide Perovskites for optoelectronic applications

Abstract: The world is facing a climate crisis and to be able to solve it society needs to decrease the use of fossil fuels and find renewable alternatives. Solar energy is a great contender for a renewable energy source since it can be harvested for eternal time. One of the problems with the solar cells available today is that they are more expensive than fossil alternatives, and the process of making them still uses a lot of resources and energy. However, in the last decade an alternative has arisen; perovskite solar cells. Due to the fact that perovskite solar cell production uses less energy and resources than the current silicon solar cell, perovskite solar cells are more cost effective. The main problem with perovskite solar cells is that they are too unstable and do not last very long. One way to stabilize them is to introduce one more cation and make hybrid perovskites. The purpose of this project was to synthesize a perovskite material with the chemical formula AA’PbI3 (A = Cs, A’ = dimethylammonium or ethylammonium) to see if any of the compositions would generate a stable black cubic phase, which is the optimal phase of the perovskite. Mesoporous N-I-P solar cells were created by a layer by layer deposition method. The perovskite layer was added using a spin-coater to deposit the perovskite solution. The films were then characterized using XRD and UV/Vis absorption spectroscopy. Due to the coronavirus pandemic of 2020, the hole transport material and gold electrode were not added to the solar cell. As a consequence of this, not all of the compositions were synthesised which also means that the results are not conclusive. It was observed that all of the films were yellow, which indicates that none of the perovskites achieved a cubic structure. An explanation could be that some parts of the synthesis needs to be done inside a glove box where the environmental variables like humidity could be controlled. The XRDs show that some films had the expected perovskite composition, while some perovskites had decomposed into its starting materials. For hybrid components and pure ethylammonium perovskite film it was harder to confirm our conclusion since no characterization of single crystals was available for these components. However, it was determined that the addition of cesium did make the perovskites more stable.