Surface repair of wide-bandgap perovskites for high-performance all-perovskite tandem solar cells

Wide-bandgap(WBG)perovskite solar cells(PSCs)play a fundamental role in perovskite-based tandem solar cells.However,the efficiency of WBG PSCs is limited by significant open-circuit voltage losses,which are primarily caused by surface defects.In this study,we present a novel method for modifying surfaces using the multifunctional S-ethylisothiourea hydrobromide(SEBr),which can passivate both Pb^(-1)and FA^(-1)terminated surfaces,Moreover,the SEBr upshifted the Fermi level at the perovskite interface,thereby promoting carrier collection.This proposed method was effective for both 1.67 and 1.77 eV WBG PSCs,achieving power conversion efficiencies(PCEs)of 22.47%and 19.90%,respectively,with V_(OC)values of 1.28 and 1.33 V,along with improved film and device stability.With this advancement,we were able to fabricate monolithic all-perovskite tandem solar cells with a champion PCE of 27.10%,This research offers valuable insights for passivating the surface trap states of WBG perovskite through rational multifunctional molecular engineering.

Recent progress of inverted organic-inorganic halide perovskite solar cells

In recent years,inverted perovskite solar cells(IPSCs)have attracted significant attention due to their low-temperature and cost-effective fabrication processes,hysteresis-free properties,excellent stability,and wide application.The efficiency gap between IPSCs and regular structures has shrunk to less than 1%.Over the past few years,IPSC research has mainly focused on optimizing power conversion efficiency to accelerate the development of IPSCs.This review provides an overview of recent improvements in the efficiency of IPSCs,including interface engineering and novel film production techniques to overcome critical obstacles.Tandem and integrated applications of IPSCs are also summarized.Furthermore,prospects for further development of IPSCs are discussed,including the development of new materials,methods,and device structures for novel IPSCs to meet the requirements of commercialization.

In-depth understanding of ionic liquid assisted perovskite film formation mechanism for two-step perovskite photovoltaics

Ionic liquids(ILs)have been widely applied in the one-step fabrication of perovskite with noticeable enhancement in the device performance.However,in-depth mechanism of ionic-liquid-assisted perovskite film formation is not well understood for also important two-step perovskite fabrication method,with better control of crystallization behavior.In this work,we introduced ionic liquid methylammonium formate(MAFa)into organic salt to produce perovskite film via a two-step method.Systematic investigations on the influence of MAFa on the perovskite thin film formation mechanism were performed.Ionic liquid is shown to assist lowering the perovskite formation enthalpy upon the density functional theory(DFT)calculation,leading to an accelerated crystallization process evidenced by in-situ UV-Vis absorption measurement.A gradient up-down distribution of ionic liquid has been confirmed by timeof-flight SIMS.Importantly,besides the surface passivation,we found the HCOO-can diffuse into the perovskite crystals to fill up the halide vacancies,resulting in significant reduction of trap states.Uniform perovskite films with significantly larger grains and less defect density were prepared with the help of MAFa IL,and the corresponding device efficiency over 23%was obtained by two-step process with remarkably improved stability.This research work provides an efficient strategy to tune the morphology and opto-electronic properties of perovskite materials via ionic-liquid-assisted two-step fabrication method,which is beneficial for upscaling and application of perovskite photovoltaics.

Vacuum-free fabrication of high-performance semitransparent perovskite solar cells via e-glue assisted lamination process

From a base material of conductive polymer(poly-(3,4-ethylenedioxythiophene):poly(styrenesulfonate),PEDOT:PSS),a flexible and high-conductivity(as low as 45Ω/sq)transparent electrode was fabricated on polydimethylsiloxane elastomer by an acid treatment and transfer process.Combined with the D-sorbitol-doped PEDOT:PSS electric glue,we successfully demonstrated a vacuum-free and ambient lamination fabrication process for semi-transparent perovskite solar cells using triple cation Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3perovskite.By this manufacturing-friendly lamination process,we fabricated semitransparent perovskite solar cell devices with power conversion efficiencies up to 16.4%and variable transparencies.

Solution process formation of high performance,stable nanostructured transparent metal electrodes via displacement-diffusion-etch process

Transparent electrodes(TEs)with high chemical stability and excellent flexibility are critical for flexible optoelectronic devices,such as photodetectors,solar cells,and light-emitting diodes.Ultrathin metal electrode(thickness less than 20 nm)has been a promising TE candidate,but the fabrication can only be realized by vacuum-based technologies to date,and require tedious surface engineering of the substrates,which are neither ideal for polymeric based flexible applications nor suitable for roll-to-roll large-scale manufacture.This paper presents high-performance nanostructured transparent metal electrodes formation via displacement-diffusion-etch(DDE)process,which enables the solution-processed sub-20-nm-thick ultrathin gold electrodes(UTAuEs)on a wide variety of hard and soft substrates.UTAuEs fabricated on flexible polyethylene terephthalate(PET)substrates show a high chemical/environmental stability and superior bendability to commercial flexible indiumtin-oxide(ITO)electrodes.Moreover,flexible organic solar cells made with UTAuEs show similar power conversion efficiency but much enhanced flexibility,in comparison to that of ITO-based devices.

Enhanced efficiency and stability of triple-cation perovskite solar cells with CsPbI_(x)Br_(3−x)QDs“surface patches”

Perovskite solar cells(PSCs)with a light-harvesting three-dimensional perovskite bulk layer as backbone component have achieved great progress in performance.Nonradiative recombination is one major place to improve efficiency and stability as they cause significant energy loss in PSCs.Additionally,an imperfection in grain boundaries will initiate device degradation.One of the most successful strategies to decrease nonradiative recombination in PSCs is the introduction of reduced dimensional perovskite(e.g.,perovskite quantum wells),benefiting the device's efficiency and stability tremendously.Here,instead of quantum wells,mixed-cation perovskites with ligand-contained CsPbBr_(x)I_(3−x)quantum dots(QDs)are prepared,which is shown to function as perovskite healing“surface patches.”Benefiting from the“surface patches”effect,the QDs-film shows reduced defects and enhancing film quality which lead to the excellent performance of solar cells(enhancing the power conversion efficiency from 19.21%of the control device to 21.71%[22.1%in reverse scan]).

Room-temperature multiple ligands-tailored SnO_(2) quantum dots endow in situ dual-interface binding for upscaling efficient perovskite photovoltaics with high V_(OC)

The benchmark tin oxide(SnO_(2))electron transporting layers(ETLs)have enabled remarkable progress in planar perovskite solar cell(PSCs).However,the energy loss is still a challenge due to the lack of“hidden interface”control.We report a novel ligand-tailored ultrafine SnO_(2) quantum dots(QDs)via a facile rapid room temperature synthesis.Importantly,the ligand-tailored SnO_(2) QDs ETL with multi-functional terminal groups in situ refines the buried interfaces with both the perovskite and transparent electrode via enhanced interface binding and perovskite passivation.These novel ETLs induce synergistic effects of physical and chemical interfacial modulation and preferred perovskite crystallization-directing,delivering reduced interface defects,suppressed non-radiative recombination and elongated charge carrier lifetime.Power conversion efficiency(PCE)of 23.02%(0.04 cm^(2))and 21.6%(0.98 cm^(2),V_(OC) loss:0.336 V)have been achieved for the blade-coated PSCs(1.54 eV E_(g))with our new ETLs,representing a record for SnO_(2) based blade-coated PSCs.Moreover,a substantially enhanced PCE(V_(OC))from 20.4%(1.15 V)to 22.8%(1.24 V,90 mV higher V_(OC),0.04 cm^(2) device)in the blade-coated 1.61 eV PSCs system,via replacing the benchmark commercial colloidal SnO_(2) with our new ETLs.

In-situ fabrication of vertical heterogeneous nickel diselenide-molybdenum diselenide architectures as bifunctional overall water-splitting electrocatalyst

Despite the rapid advances in electrocatalysts based on two-dimensional(2D)transition metal dichalco-genides(TMDs)materials,they are subject to serious aggregation,poor conductivity and the presence of inactive basal planes.Herein,we have successfully demonstrated the in-situ construction of NiSe_(2)-MoSe_(2) heterostructure arrays on carbon cloth(NiSe_(2)-MoSe_(2)/CC)by a facile two-step hydrothermal process.The presence of the synergistic effect in the heterostructures effectively optimizes the poor conductivity and hydrophilicity,and thus enables fast electron transfer,leading to enhanced electrochemical reaction.Fur-thermore,density functional theory calculations reveal that the electrons redistribution at the heterojunc-tion interface and the reduced Gibbs free energy of hydrogen adsorption for hydrogen evolution reaction(HER)/the Gibbs free energy change value of rate-determining step for oxygen evolution reaction(OER),thus enhancing the HER/OER catalytic activity.Importantly,the device displays a good performance with a low overpotential of 98 and 310 mV for HER and OER,respectively,and a low cell voltage of 1.59 V for its corresponding electrolyzer(10 mA cm^(-2)).This work presents the high-performance water splitting of bifunctional electrocatalysts based on 2D TMDs materials and offers a novel design concept of interface engineering.