The effect of ethylene-amine ligands enhancing performance and stability of perovskite solar cells
We develop an approach that combines molecular dimensionality control and interfacial passivation of perovskite layers using a novel post-device treatment (PDT) with the vapour of ethylene-amine salts of different carbon chain lengths to improve both efficiency and stability of the PSCs. The effect of a series of ligand vapours including ethylenediamine (EDA), diethylenetriamine (DETA) and triethylenetetramine (TETA) was systematically investigated. A thin hydrophobic two-dimensional (2D) perovskite capping layer formed in the device after the 3D perovskite was exposed to the vapour of long chain ethylene-amine molecules, such as DETA and TETA, which protected the underlying bulk 3D perovskite layer from moisture attack. An improved energy level alignment was obtained in the treated devices and that a reduced density of defects was present in the perovskite after treatment with DETA and TETA vapours. Consequently, enhanced efficiency from 17.07% to 18.09% (DETA) and improved moisture stability with PCE retention from 73.8% to 90.0% (TETA) under a relative humidity>65% for 1000 h were achieved by this vapour treatment respectively.
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