Perfection of Perovskite Grain Boundary Passivation by Rhodium Incorporation for Efficient and Stable Solar Cells

Organic cation and halide anion defects are omnipresent in the perovskite films,which will destroy perovskite electronic structure and downgrade the properties of devices.Defect passivation in halide perovskites is crucial to the application of solar cells.Herein,tiny amounts of trivalent rhodium ion incorporation can help the nucleation of perovskite grain and passivate the defects in the grain boundaries,which can improve efficiency and stability of perovskite solar cells.Through first-principle calculations,rhodium ion incorporation into the perovskite structure can induce ordered arrangement and tune bandgap.In experiment,rhodium ion incorporation with perovskite can contribute to preparing larger crystalline and uniform film,reducing trap-state density and enlarging charge carrier lifetime.After optimizing the content of 1% rhodium,the devices achieved an efficiency up to 20.71% without obvious hysteresis,from 19.09% of that pristine perovskite.In addition,the unencapsulated solar cells maintain 92% of its initial efficiency after 500 h in dry air.This work highlights the advantages of trivalent rhodium ion incorporation in the characteristics of perovskite solar cells,which will promote the future industrial application.

Enhancement of Curie Temperature under Built-in Electric Field in Multi-Functional Janus Vanadium Dichalcogenides

Functionalized two-dimensional materials with multiferroicity are highly desired to be next-generation electronic devices.Here we theoretically predict a family of Janus vanadium dichalcogenides VXX'(X/X'=S,Se,Te)monolayers with multiferroic properties,combing ferromagnetism,ferroelasticity and piezoelectricity.Due to the unpaired electrons on the V atom,the Janus VXX'monolayers have intrinsic long-range ferromagnetic orders.Particularly,the Curie temperature of 1T-VSeTe monolayer is up to 100 K,which is greatly higher than 2D 1T-VSe2 and 1T-VTe2.Furthermore,the six Janus VXX'monolayers have similar crater-like ferroelastic switching curves.Compared to black phosphorus,2H-VSSe monolayer has the similar ferroelastic switching signal and 4 times lower energy barrier.In addition,the out-of-plane piezoelectricity induced by the structure asymmetry in the vertical direction gives the 2H-VXX'monolayers the potential to be piezoelectric materials.It is found that a built-in electric field in the vertical direction due to the different electronegativity values of chalcogen atoms induces the changes of electronic structures,which leads to the appearance of three different types of band gaps in the three H-phase structures.Recently,the experimental growth of the Janus MoSSe monolayers and the electrochemical exfoliation of ferromagnetic monolayered VSe2 make the Janus VXX'monolayers possibly fabricated in experiments.

Three-dimensional/one-dimensional perovskite heterostructures for stable tri-state synaptic memristors

Memristors have great potential in neural network computation.Perovskite memristors exhibit excellent resistive-switching(RS)properties between high resistance state(HRS)and low resistance state(LRS)state under applied voltage due to the extraordinary ion migration and superior charge transfer.However,the stability issue of traditional three-dimensional(3D)perovskites is still challenging.Here,one-dimensional(1D)(CH_(3))_(3)SPbI_(3)perovskite passivation layer was in-situ formed on 3D perovskite film,which was further applied in stable synaptic memristor.The memristor was provided with three resistance states due to the heterojunction electric field coupled with ion migration.The on/off ratio of memristors was obviously improved from 10 to over 60.The RS characteristics of 3D/1D perovskite memristor remained unchanged after 10^(3)s read and 300 switching cycles.The 3D/1D perovskite memristor effectively exhibited versatile synaptic plasticity behaviors including long-term potentiation,long-term depression and paired-pulse facilitation by controlling the input voltages.Notably,the novel device provides a new candidate for next-generation neuromorphic computing.