Research achievements and highlights

fromProfessor Wei Zhanhua's team from Huaqiao UniversityLeader, published in the top issue《Nature CommunicationsHow to translateThe theme of the article is《

Ultrathin polymer membrane for improved hole extraction and ion blocking in perovskite solar cells》.Regarding the current high efficiencyn-i-pPerovskite type solar cellsLong term operational lifespan is limitedThe problem mainly stems from the perovskite and doped hole transport layer（HTL）In heterojunctionsion diffusionThis will lead toHTL7The decrease in conductivity and loss of perovskite components. To address this critical challenge, Professor Wei Zhanhua's teamDeveloped and researched an ultra-thin (approximately)Nano)pType polymer intermediate layer（D18

）.•D18

The ultra-thin intermediate layer effectively suppresses the diffusion of lithium, methylammonium, formamidine, and iodide ions between the layers.•D18Improved perovskite/HTL

The band arrangement of the interface promotes more efficient hole extraction.•Based on this innovative design, perovskite solar cells have achieved successGundam26.39%(Certified as26.17%）Power conversion efficiency(Small area devices) and25.02%

Efficiency of large-area devices. 1100 •The device operates continuously under maximum power point trackingAfter hours, stillMaintaining initial efficiency

95.4%Showing significant stability improvement.•throughQFLSAnalysis of Quasi Fermi Level SplittingIt has been confirmedVOCThe improvement is not only attributed to the reduction of non radiative recombination, but also benefited from

D18

Optimization of band arrangement in the middle layer.research teamThe research team mainly comes fromHuaqiao University，Wei Zhan PaintingandXie LiqiangThe professor is a co-author of this researchcorresponding authorAnd in collaboration with City University of Hong Kong

Alex. K.-Y. Jen

Professors and other researchers collaborate together.Research BackgroundIn the field of perovskite solar cells, especially in high-efficiency applications

n-i-pIn terms of structure, it faces some significant difficulties and challenges:•Limited operating lifespan: Efficientn-i-pAlthough perovskite solar cells have efficiencyThe operational lifespan is relatively limitedIt's better

p-i-nThe battery is stable.•Perovskite and hole transport layer（HTL）There is ion diffusion between them, leading to

HTLDecreased conductivity and loss of perovskite components.•commonly used HTLmaterialSpiro-OMeTADFluffy and thick structureEasy to occurDoping agent loss, and

Insufficient ion blocking ability.•In order to improve stabilityreplace

Spiro-OMeTADMay lead to a significant decrease in efficiency.•Perovskite materials themselves haveIonic bond characteristics, relatively soft lattice, prone to ion migrationFurthermore, it corrodes

HTLAnd electrodes.•The existing interface materials are

It is difficult to balance the suppression of ion interdiffusion and the maintenance of efficient hole extraction

.solutionRegarding the previously mentionedn-i-pThe difficulties and challenges encountered by perovskite solar cells have been proposedInsert ultra-thinpType polymer intermediate layer（D18

）The core solution. Mainly focusing on the following aspects:•Building an ion barrier layer:利用D18Polymer in perovskite layer and hole transport layer（HTLMainly, it isSpiro-OMeTAD7）Form a gap between themUltra thin (approximately)Nano sized and dense membrane.D18The unique molecular structure of polymers, especially theirDTBT Fused-RingThe strength formed by the unitπ–πstack, which helps to form a tighter film, thusEffectively block ions in perovskite, such as lithium, methylammonium, formamidine, and iodide ions, from enteringHTLThe diffusionThis blocking effect can protect

HTLProtect from ion corrosion and reduce the loss of perovskite components, thereby improving the stability of the device.•Optimize interface energy level arrangement:In addition to its ion blocking function,D18The middle layer is also designed to be able toImproving perovskite andHTLThe arrangement of energy levels between themResearch has found that,D18The energy levels of adjacent perovskites andSpiro-OMeTADThere is good matching between them. by introducingD18can

Reduce energy loss at the interface and promote more efficient hole extraction.•Adopting the hot spin coating process:To ensureD18The middle layerDensity and uniform coverageThe research team adoptsHot spin coating processCome and deposit

D18film. This method can form better interface contact, improve ion barrier effect and hole transport efficiency.•verificationD18：The research team has demonstrated through experiments that,D18inThe ability to suppress ion diffusion is significantly better than commonly used polymersHTLMaterials, such asP3HTandPTAAThis is attributed to

D18

Stronger intermolecular interactions enable the formation of denser thin films.Experimental process and steps

•Material preparation:○research teamsynthesisAs a key material for the intermediate layer

D18polymer○preparationOther required materials for perovskite solar cells, such as tin salts (used for...)SnO2Electronic transport layer, lead iodide（

PbI2）And various organic salts (used to form perovskite).○prepare, compound, formulateDifferent concentrations of

D18Solution, used for subsequent thin film deposition.

1. •Device preparation:firstFTODeposition on glass substrate

2. SnO2electron transport layerthroughTwo-step solution methodinSnO2On the layerPreparation of Perovskite Thin FilmsAnd use itOAI

3. Perform surface passivation treatment.In order to introduceD18In the middle layer, researchers willhotD18Solution spin coating on passivated perovskite thin filmThey found thatUse hot spin coating and appropriate concentrationD18Solution plays a crucial role in forming a dense and uniform structureD18The middle layer is very importantThey observed that different molecular weightsD18There are differences in solubility and film-forming properties, so we ultimately chose D18-M(Medium molecular weight)As the main interface material. They also discovered that

4. D18Spin coating on cold perovskite thin films is prone to agglomeration.inD18On the layerspin coatingSpiro-OMeTAD

5. Hole transport layer.

Steam gold or silverElectrode, complete the preparation of solar cell devices.

•Research on ion barrier effect:To verify D18Researchers have designed an experiment to observe the ion blocking ability of [substance]PbBr2andFAI

The reaction.○They first lay it on a glass substratedepositionPbBr2

film.○Then, in some partsPbBr2On the filmSpin coating different concentrationsD18TheP3HTandPTAA

Polymer filmAs a comparison.○Next, in these areas covered with different materialsPbBr2On the filmspin coatingFAIsolutionObserve whether there is a color change. Observed coverageD18ofPbBr2The film isFAIAfter spin coatingThere is no obvious color change, indicatingD18Effectively blocked ion diffusion. In contrast, higher concentrations are requiredP3HTand

PTAAOnly then can a similar blocking effect be achieved.○Researchers also utilizeXX-ray diffraction(XRD)Technical analysis of the crystal structure changes of these thin films further confirmsD18At a certain concentration, it can preventPbBr2andFAIThe reaction between them. They also studied under thermal stress

D18The ability to block different ions.•

D18Thin film characteristic analysis:○useScanning electron microscope(SEM)Observed itD18The coverage on the surface of perovskite confirms that it can be obtained through thermal spin coatingUniform and denseD18

film.○useHigh resolution transmission electron microscopeHRTEMmeasured7D18The thickness of the intermediate layer is approximatelyNanoAnd observed thatD18Close contact with perovskite grains and grain boundaries. They also confirmed in the follow-upSpiroDuring the sedimentation process, ultra-thin

D18The middle layer will not be damaged. ○through Surface potential microscope(KPFM)Analyzed the distribution of surface potential of perovskite and found thatD18Can form with the surface of perovskite

Uniform contact

.Research results and characterizationQuasi Fermi level splitting(Quasi-Fermi Level Splitting, QFLS)

Compared to open circuit voltage(Voc)Evaluate non radiative composite losses and understand them

D18The influence of the intermediate layer on the open circuit voltage.picture3dDisplayed the control group andD18Measurement of componentsVocandQFLSPresented the control group（Control）AndD18Open circuit voltage of components（VOC）And based on the photoluminescence quantum efficiency（PLQY）Calculated quasi Fermi level splitting（QFLS）.D18The components of the groupQFLSThe value has increased compared to the control group20 meVThis is related tomeasuredVOC improved33 mVMatch. This indicatesVOCThe improvement is not only attributed to the reduction of non radiative composite losses, but also to

Improved interface energy level arrangementofEnlitechWe are about to launch a brand new product

QFLSMeasuring instruments!3Enlitech QFLS-MaperCan be achieved in a short period of timeQuickly generate quasi Fermi levels within seconds（2QFLS）The image is not availableReconstruct within minutesPseudo J-VCurves allow you to easily grasp the theoretical efficiency limit and non radiative composite losses of materials. Not only does it support measurementiVOCThePLImages and PLQYBy utilizing multimodal parameters and presenting them in highly visual form, researchers can accurately analyze and optimize the performance of solar cells and other advanced optoelectronic components.

2. Follow us for more latest news!current density-voltage

(J-V)curveThe research team utilizedEnliTechofAAASolar simulator SS-XconductJ-V

Measurement of curves,Evaluate the core performance parameters of solar cellspicture4aCompared the control group andD18Small area perovskite solar cellsJ-VCurves, including reverse scan and forward scan. introduceD18After the middle layer, the best D18The implementation of small area devices has been achieved26.39%(Reverse scan) and26.12%The power conversion efficiency (forward scan), fill factor from80.37%raise to83.92%The open circuit voltage is from1.152 Vraise to1.185 V

，Thus improving overall efficiency.•picture4cShowcased a large area(1 cm2)Perovskite solar cellsJ-VThe curve also compared the control group andD18Group. Even in large areas, use

3. D18The devices in the middle layer still exhibit high efficiency.

External quantum efficiency(External Quantum Efficiency, EQE)The research team usesEnliTechofEQEsystemQE-R，Measure the response of solar cells under different wavelengths of light and integrate to calculate the short-circuit current density

(Jsc).pictureS 23：Compared the control groupD18External quantum efficiency of perovskite solar cells（EQE）Spectrum. Within the entire visible light absorption range,D18The components of the groupEQECompared to the control group, there has been an improvement. pointsEQEThe short-circuit current density obtained from the spectrum and

J-VThe values measured by the curve are consistent.research findings: D18The integrated short-circuit current density of the component is25 25.86 mA cm?, with

J-V

The results of the curve are consistent.Other characterizations•XX-ray diffraction

(XRD)：Analyze the crystal structure and phase purity of perovskite thin films, and evaluate the degradation of devices under thermal stress. Also used for evaluationD18The ion blocking effect. The results confirmD18The intermediate layer can effectively suppress the decomposition of perovskite under thermal stress,And at a certain concentration, it canpreventPbBr2andFAIIon exchange reaction between them.(Image)1c, picture2b, picture

S 10）•Flight time secondary ion mass spectrometry

(ToF-SIMS)：Analyze the distribution of elements within the device layer and study the migration behavior of ions during aging. The results indicate that under thermal stress,In the perovskite of control group devicesI-andFA+Ions are clearly oriented towardsSpiro-OMeTADLayer diffusionButD18The migration of ions in the device is significantly inhibited.(Image)2eThe2f, picture

S 13）•photoluminescence(PL)Time-resolved photoluminescence

(TRPL)：Study the carrier dynamics and interface charge transfer efficiency of perovskite. introduceD18After the middle layer,The exciton recombination of perovskite is effectively suppressed, and the efficiency of charge separation and extraction is improved.(Image)3a, picture3b, picture

S 19）•Kelvin probe force microscope

(KPFM)：measurementHTLSurface potential of the surface, evaluated after agingHTLChanges in work function. after agingControl group componentsSpiro-OMeTADThe surface potential significantly decreases, and the work function also significantly decreases，D18Component assemblySpiro-OMeTADThe surface potential and work function have relatively small changes. (Image)2hThe

2i）•Scanning electron microscope

(SEM)：Observe the surface morphology of the thin film and the cross-sectional structure of the device. Image confirmationD18The intermediate layer can form a dense thin film, effectively covering the surface of perovskite and protecting its morphology after aging. (Image)2d, picture

S5

）conclusionThis study has been successfully conducted in an efficient mannern-i-pIntroducing a layer in perovskite solar cellsExtremely thinD18

Polymer intermediate layerThis innovative design has brought significant progress:•Significantly improved the stability of solar cells：D18The middle layer effectivelyBlocked the perovskite layer and the tunnel transport layer(HTL)Ionic diffusion between themThus protecting the perovskite material andHTLFree from degradation. Experimental evidence shows that compared to noneD18Devices in the middle layer, using

D18The device can maintain higher efficiency under continuous illumination and high temperature conditions.•Improved energy conversion efficiency：D18middle layerOptimized perovskite andHTLThe arrangement of energy levels between themThis promotes the effective extraction of holes and reduces interface energy loss. In the end, the solar cell manufactured by the research team obtainedGundam26.39% (Verified as26.17%)Power conversion efficiencyAnd over a large area(1Square centimeters)The efficiency of the device has also reached

25.02%

.