Research Projects

Solution-processed inorganic–organic hybrid perovskite solar cells (PSC) have rapidly progressed in efficiency from 3.8% in 2009 to over 26% in recent years. While such power conversion efficiencies have been achieved in a small area lab cell, translation of this performance to large area cells/modules is a challenge. The process starts with the preparation of a precursor solution in a suitable solvent. Depending on the properties of the solvent, the precursor solution forms a variety of co-ordination complexes which are converted into perovskite crystals via any number of methods. These include (i) temperature reduction, (ii) solvent evaporation or (iii) addition of anti-solvent. A number of factors including solvent composition, nature of anti-solvent, presence of additives, substrate, temperature, etc., affect film coverage, grain growth, crystallinity, traps passivation. Currently design of synthesis processes is confined to purely empirical trial-and-error strategies. An understanding the solution chemistry during perovskite crystallization is a key ingredient to the development of a solution based industrial manufacturing of PSCs. The focus of this proposal is on solution based synthesis of perovskite materials which is used to develop thin films of perovskites on suitable substrates. Crystal nucleation is the earliest stage during any crystallization process. It is expected that among other factors, knowledge of the mechanism and rate of crystal nucleation can help uncover the role of solution chemistry on the final morphology of the perovskite material. Molecular simulations act as a digital microscope and can provide atomistic details of the structure of the critical nucleus and the nucleation pathway. Hence molecular simulations are widely used to study crystal nucleation. The objective of this proposal is to develop and apply computational methods for simulating nucleation of perovskites from solutions and gain insights into the nucleation pathway and role of solvents. The simulations will be complemented by in-situ spectroscopic experiments on the perovskite intermediate phases. The results from these experiments will guide the simulation setups and vice-versa. The model perovskite for our study will be Methylammonium Lead Iodide MAPbI₃. The common solvents used in perovskite synthesis are dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), acetonitrile (ACN) and urea. In our study we will consider between two and three solvents from the above pool. We will then repeat the calculation by simulating MAPbI₃ nucleation on the surface of NiO. NiO is the most commonly used hole transport layer (HTL) in a PSC and perovskite films are grown on top of this HTL. The research outcome from this project will contribute significantly towards the development of highly efficient low cost solar photovoltaic cells.