High Efficiency Perovskite Solar Cells For Space Applications

Abstract

Solar cells have been powering satellites since the beginning of space exploration. As “commercial” space activities are increasing driven by decreasing launch and manufacturing costs, new space solar cell technologies that are of low cost will be needed. Organometal halide perovskite solar cells (PSCs) are promising for this due to their high efficiencies, low manufacturing cost, and radiation hardness warranting research and development. For this, the first experimental work of this thesis reports passivation strategies for perovskites fabricated by gas-quenching to reduce the use of toxic solvent for high efficiency cell demonstration. The strategies involve the incorporation of potassium iodide (KI)) in the perovskite and the deposition of n-hexylammonium bromide (HABr) onto the perovskite surface producing an efficiency of 23.6% for champion device. For better stability critical for operations in space, the progress and opportunities of Cs incorporated perovskites were reviewed, thereby inspiring the demonstration of CsFA perovskite cells optimised on sub-millimetre thin (175-μm) sapphire substrate as part of the second experimental work. High power-to-weight ratios over 200 mW/g were demonstrated - highest amongst PSCs used for proton irradiation studies. The last experimental work compares radiation hardness of 3 different types of hole transport materials (HTMs) for PSCs. HTM with tris(pentafluorophenyl)borane (TPFB) as a dopant was found to be more radiation tolerant than that with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dopant. The more superior cells also recovered from radiation damage via thermal vacuum that can be facilitated by solar irradiation on low earth orbit. Thermal admittance spectroscopy (TAS) and deep-level transient spectroscopy (DLTS) were used to characterize radiation-induced defects in PSCs for the first time at the time of reporting. The thesis concludes with an outlook for future work based on findings from this thesis.