Research On Highly Efficient And Stable All-inorganic CsPbX₃ Perovskite Solar Cells

Organic-inorganic hybrid halide perovskites have attracted a great deal of attention due to their large absorption coefficient,adjustable direct band gap,high charge mobility,abundant material resources,and so on.The power conversion efficiency(PCE)of the perovskite solar cells has been increased from 3.8%to 23.7%since its first report in 2009.However,stability remains to be the main hurdle for its commercialization.Therefore,we attempt to replace the organic components with Cs to fabricate the all inorganic perovskite solar cells with stable performance.However,among inorganic perovskite,the most phase-stable inorganic perovskites based on CsPbBr3 and CsPbBr2I are wide bandgap semiconductors,excluding the possibility to harvest light in the long wavelength spectrum,hence low solar cell efficiency.Moreover,the CsPbl3 is found to be unstable in the black perovskite phase,it phase transformed into non-perovskite yellow phase even in ambient atmosphere.The CsPbI2Br perovskite possesses advantages in its suitable band gap(1.91 eV)and phase stability.Therefore,we chose CsPbI2Br and CsPbl3 as the light absorption layer and optimize all inorganic PSCs.The main contents and results of the dissertation are summatized as follows:(1)The moisture resistance of the CsPbI2Br PSC is designed through an effective PEACl interface treatment between the CsPbI2Br film and the HTL.Compared with the reference device,the optimized device achieved an undiminished PCE of 14.05%and dramatically improved stability in humid conditions.Further study found that the PEACl plays the beneficial roles of(i)assisting the formation of a hydrophobic layer on the CsPbI2Br surface,and(ii)controlling the crystallization of the film and lattice shrinkage induced by the Cl' doping effect.We believe our findings provide an effective strategy to address the main barrier to the practical application of inorganic perovskite devices,which may also be applicable to other inorganic perovskite-based optoelectronic devices beyond photovoltaics.(2)By optimizing with Br concentration,CsPbI2.85Br0.15 PSCs are fabricated with Eloss as low as 0.58 eV,and the best performing device demonstrates a record PCE of 17.17%.Simultaneously,it also plays a positive role in the stability of devices after continuous light soaking or long-term exposure in ambient condition.Further characterizations found that the role of Br is effectively suppressing bulk trap-assisted nonradiative recombination and lattice strain relaxation.This kind of optimization method are greatly beneficial for their various scientific and application investigations in inorganic perovskite devices.With further exploration to furnish an excellent mix of performance,material abundance and scalable fabrication ultimately,inorganic CsPbX3 PSCs is potentially becoming the prevailing thin-film technology of the next-generation photovoltaic devices or other optoelectronic devices in the future.