Proceedings of Perovskite Thin Film Photovoltaics (ABXPV17)
Publication date: 18th December 2016
The big potential for low-cost production in the perovskite technology is due the possibility of deposited the major components of device with a low-temperature coating process using inexpensive, abundant materials. The possibility of use solution processed methods makes perovskites a promising candidate for inexpensive printing or roll to roll industrial mass solar cell production on light weight, large area and flexible substrates. Precursor solvent, replacement of antisolvent treatment, annealing process and additives are the main parameters that significantly present influence on organo-metal halide perovskite crystallization. A suitable combination of green, low cost and effective precursor solvents, anti-solvents, additives, direct or multi-step annealing processing are needed in order to improve the crystallization and morphology of up-scalable perovskite films. In this work we focus on Hansen Solubility Parameters (HSP) approach as a tool for the design of green ink formulations containing organo-metal halide perovskites. Solvent engineering based on HSPs has been used for achieving an increase of perovskite concentration, a better control of the evaporation rate, and to promote a better crystallization of solution processed perovskite films. A list of potential green solvents for CH3NH3PbI3 perovskites as an alternative to hazardous DMF, DMSO, NMP and DMAC, among others, has been obtained. Processing parameters (such as boiling point, relative evaporation rate, etc.) together with environmental and toxicological aspects have also been considered. Furthermore, thin films of the most promising green solvents were fabricated and characterized. The results for solubility tests and thin film deposition are shown and compared to the use of common toxic solvents. Solvent engineering by HSP considering solubility/insolubility, environmentally friendly solvents, and influence of processing and annealing parameters will help to improve the macromolecular order of perovskite structures replacing toxic solvents that are not industrially up-scalable. The development of this innovative solvent engineering approach will contribute to improve reliability on the wet processing by using more environmentally friendly inks for perovskite absorbers.