Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids)for Efficient and Stable Perovskite Solar Cells

The inevitable ion migration that occurs within ionic polycrystalline perovskite film results in inferior longterm stability of perovskite solar cells(PVSCs)that cannot meet the commercial requirements.Here,a novel poly(ionic liquid)named poly-1-vinyl-3-propyltrimethoxysilane imidazolium chloride(PImIL-SiO)is first introduced into perovskite to strengthen grain boundaries(GBs)and construct dual-functional barriers against internal ion migration and external moisture erosion for fabricating highly efficient and stable PVSCs.PImIL-SiO-containing imidazoliumcations and pendant siloxane groups contribute to passivation of bulk defects and anchoring of GBs,which effectively hinders ion migration channels,thus reducing perovskite film phase separation and device hysteresis.Furthermore,the intrinsically hydrophobic PImIL-SiO automatically forms a secondary protective barrier to endow the perovskite film with ultrahigh moisture corrosion resistance through the hydrolyzation reaction of siloxane with the permeated moisture.Consequently,the PImIL-SiO-modified PVSCs achieve a champion power conversion efficiency(PCE)of 22.46%,accompaniedby excellent thermal andhumidity stabilities where the non-encapsulated devices retain 87%of the initial PCE after aging at 85℃for 250 h and>85%of the initial PCE over 1100 h in air with a relative humidity of 50–70%.

Efficient and Air-Stable Planar Perovskite Solar Cells Formed on Graphene-Oxide-Modified PEDOT:PSS Hole Transport Layer

As a hole transport layer, PEDOT:PSS usually limits the stability and efficiency of perovskite solar cells(PSCs) due to its hygroscopic nature and inability to block electrons. Here, a graphene-oxide(GO)-modified PEDOT:PSS hole transport layer was fabricated by spin-coating a GO solution onto the PEDOT:PSS surface. PSCs fabricated on a GO-modified PEDOT:PSS layer exhibited a power conversion efficiency(PCE) of 15.34%, which is higher than 11.90% of PSCs with the PEDOT:PSS layer.Furthermore, the stability of the PSCs was significantly improved, with the PCE remaining at 83.5% of the initial PCE values after aging for 39 days in air. The hygroscopic PSS material at the PEDOT:PSS surface was partlyremoved during spin-coating with the GO solution, which improves the moisture resistance and decreases the contact barrier between the hole transport layer and perovskite layer. The scattered distribution of the GO at the PEDOT:PSS surface exhibits superior wettability, which helps to form a high-quality perovskite layer with better crystallinity and fewer pin holes. Furthermore, the hole extraction selectivity of the GO further inhibits the carrier recombination at the interface between the perovskite and PEDOT:PSS layers. Therefore, the cooperative interactions of these factors greatly improve the light absorption of the perovskite layer, the carrier transport and collection abilities of the PSCs, and especially the stability of the cells.

STUDY OF DEGRADATION MECHANISM AND PACKAGING OF ORGANIC LIGHT EMITTING DEVICES

Organic Light Emitting Devices (OLED) have attracted much attention recently, for their applications in futureFlat Panel Displays and lighting products. However, their fast degradation remained a major obstacle to theircommercialization. Here we present a brief summary of our studies on both extrinsic and intrinsic causes for the fastdegradation of OLEDs. In particular, we focus on the origin of the dark spots by 'rebuilding' cathodes, which confirms thatthe growth of dark spots occurs primarily due to cathode delamination. In the meantime, we recapture the findings from thesearch for suitable OLED packaging materials, in particular polymer composites, which provide both heat dissipation andmoisture resistance, in addition to electrical insulation.

Improving performance of Cs_(2)AgBiBr_(6)solar cell through constructing gradient energy level with deep-level hole transport material

The valence band offset between Cs_(2)AgBiBr_(6)and hole transport layer(HTL)is approximately 1.00 e V,which results in high energy loss and is identified as one of the bottle necks of Cs_(2)Ag BiBr_(6)perovskite solar cell(PSC)for achieving high power conversion efficiency(PCE).To tackle this problem,we propose the optimization of the energy level alignment by designing and synthesizing novel deep-level hole transport materials(HTMs).The sole introduction of deep-level HTMs successfully reduces the valence band offset between Cs_(2)Ag Bi Br_(6)and HTL,but induces the increased valence band offset at HTL/Au interface,limiting the PCE improvement.To further solve the problem and improve the PCE,the gradient energy level arrangement is constructed by combining the newly developed deep-level HTM 6,6’-(3-((9,9-dimethyl-9H-fluoren-3-yl)(4-methoxyphenyl)amino)thiophene-2,5-diyl)bis(N-(9,9-dimethyl-9H-fluoren-2-yl)-N,9-bis(4-methoxyphenyl)-9H-carbazol-3-amine)(TF)with 2,2’,7,7’-tetrakis(N,N’-dipmethoxyphenylamine)-9,9-spirobifluorene(Spiro-OMeTAD).Through optimization,an impressive PCE of 3.50%with remarkably high open-circuit voltage(V_(oc))and fill factor(FF)is achieved,qualifying it among the best pristine Cs_(2)AgBiBr_(6)PSCs.

Well-designed g-C_(3)N_(4)nanosheet incorporated Ag loaded Er_(0.05)La_(0.95)FeO_(3)heterojunctions for isoamyl alcohol detection

Because the volatile content of isoamyl alcohol increases sharply on the seventh day of wheat mildew infection,isoamyl alcohol can be used as an early biomarker of wheat mildew infection.Currently,only a few sensors for isoamyl alcohol detection have been reported,and these sensors still suffer from low sensitivity and poor moisture resistance.Herein,the isoamyl alcohol sensitivity of 5 at%Er@LaFeO_(3)(ELFO)was enhanced by loading Ag nanoparticles on the surface of the ELFO microspheres,while the optimal operating temperature was reduced.The moisture resistance of Ag/ELFO was improved by the incorporation of g-C_(3)N_(4)nanosheets(NSs)on the surface of Ag/ELFO through electrostatic self-assembly.Given the requirements for practical applications in grain granaries,the sensing behavior of a Ag/ELFO-based sensor incorporating g-C_(3)N_(4)NSs at 20%relative humidity(RH)was systematically studied,and the sensor demonstrated excellent repeatability,long-term stability,and superior selectivity(791 at 50 ppm)for isoamyl alcohol with a low limit of detection(LOD=75 ppb).Furthermore,the practical results obtained for wheat at different mildew stages further confirmed the potential of the g-C_(3)N_(4)/Ag/ELFO-based sensor for monitoring the early mildew stage of wheat.This work may offer guidance for enhancing the moisture resistance of gas-sensitive materials through the strategy of employing composite nanomaterials.