Non-destructive buffer enabling near-infrared-transparent inverted inorganic perovskite solar cells toward 1400 h light-soaking stable perovskite/Cu(In,Ga)Se_(2) tandem solar cells

Near-infrared(NIR)transparent inverted all-inorganic perovskite solar cells(PSCs)are excellent top cell candidates in tandem applications.An essential challenge is the replacement of metal contacts with transparent conductive oxide(TCO)electrodes,which requires the introduction of a buffer layer to prevent sputtering damage.In this study,we show that the conventional buffers(i.e.,small organic molecules and atomic layer deposited metal oxides)used for organic-inorganic hybrid perovskites are not applicable to all-inorganic perovskites,due to non-uniform coverage of the vulnerable layers underneath,deterioration upon ion bombardment and moisture induced perovskite phase transition,A thin film of metal oxide nanoparticles by the spin-coating method serves as a non-destructive buffer layer for inorganic PSCs.All-inorganic inverted near-infrared-transparent PSCs deliver a PCE of 17.46%and an average transmittance of 73.7%between 780 and 1200 nm.In combination with an 18.56%Cu(In,Ga)Se_(2) bottom cell,we further demonstrate the first all-inorganic perovskite/CIGS 4-T tandem solar cell with a PCE of 24.75%,which exhibits excellent illumination stability by maintaining 86.7%of its initial efficiency after 1400 h.The non-destructive buffer lays the foundation for efficient and stable NIR-transparent inverted inorganic perovskite solar cells and perovskite-based tandems.

Chlorofullerene C_(60)Cl_(6) Enables Efficient and Stable Tin-Based Perovskite Solar Cells

Tin-based perovskite solar cells(TPSCs)have received great attention due to their eco-friendly properties and high theoretical efficiencies.However,the fast crystallization feature of tin-based perovskites leads to poor film quality and limits the corresponding device performance.Herein,a chlorofullerene,C_(60)Cl_(6),with six chlorine attached to the C_(60)cage,is applied to modulate the crystallization process and passivate grain boundary defects of the perovskite film.The chemical interactions between C_(60)Cl_(6)and perovskite components retard the transforming process of precursors to perovskite crystals and obtain a high-quality tin-based perovskite film.It is also revealed that the C_(60)Cl_(6)located at the surfaces and grain boundaries can not only passivate the defects but also offer a role in suturing grain boundaries to suppress the detrimental effects of water and oxygen on perovskite films,especially the oxidation of Sn^(2+)to Sn^(4+).As a result,the C_(60)Cl_(6)-based device yields a remarkably improved device efficiency from 10.03%to 13.30%with enhanced stability.This work provides a new strategy to regulate the film quality and stability of TPSCs using functional fullerene materials.

Role of self-assembled molecules’anchoring groups for surface defect passivation and dipole modulation in inverted perovskite solar cells

Inverted perovskite solar cells have gained prominence in industrial advancement due to their easy fabrication,low hysteresis effects,and high stability.Despite these advantages,their efficiency is currently limited by excessive defects and poor carrier transport at the perovskite-electrode interface,particularly at the buried interface between the perovskite and transparent conductive oxide(TCO).Recent efforts in the perovskite community have focused on designing novel self-assembled molecules(SAMs)to improve the quality of the buried interface.However,a notable gap remains in understanding the regulation of atomic-scale interfacial properties of SAMs between the perovskite and TCO interfaces.This understanding is crucial,particularly in terms of identifying chemically active anchoring groups.In this study,we used the star SAM([2-(9H-carbazol-9-yl)ethyl]phosphonic acid)as the base structure to investigate the defect passivation effects of eight common anchoring groups at the perovskite-TCO interface.Our findings indicate that the phosphonic and boric acid groups exhibit notable advantages.These groups fulfill three key criteria:they provide the greatest potential for defect passivation,exhibit stable adsorption with defects,and exert significant regulatory effects on interface dipoles.Ionized anchoring groups exhibit enhanced passivation capabilities for defect energy levels due to their superior Lewis base properties,which effectively neutralize local charges near defects.Among various defect types,iodine vacancies are the easiest to passivate,whereas iodine-substituted lead defects are the most challenging to passivate.Our study provides comprehensive theoretical insights and inspiration for the design of anchoring groups in SAMs,contributing to the ongoing development of more efficient inverted perovskite solar cells.

Fast and Balanced Charge Transport Enabled by Solution-Processed Metal Oxide Layers for Efficient and Stable Inverted Perovskite Solar Cells

Metal oxide charge transport materials are preferable for realizing long-term stable and potentially low-cost perovskite solar cells(PSCs).However,due to some technical difficulties(e.g.,intricate fabrication protocols,high-temperature heating process,incompatible solvents,etc.),it is still challenging to achieve efficient and reliable all-metal-oxide-based devices.Here,we developed efficient inverted PSCs(IPSCs)based on solution-processed nickel oxide(NiO_(x))and tin oxide(SnO_(2))nanoparticles,working as hole and electron transport materials respectively,enabling a fast and balanced charge transfer for photogenerated charge carriers.Through further understanding and optimizing the perovskite/metal oxide interfaces,we have realized an outstanding power conversion efficiency(PCE)of 23.5%(the bandgap of the perovskite is 1.62 eV),which is the highest efficiency among IPSCs based on all-metal-oxide charge transport materials.Thanks to these stable metal oxides and improved interface properties,ambient stability(retaining 95%of initial PCE after 1 month),thermal stability(retaining 80%of initial PCE after 2 weeks)and light stability(retaining 90%of initial PCE after 1000 hours aging)of resultant devices are enhanced significantly.In addition,owing to the low-temperature fabrication procedures of the entire device,we have obtained a PCE of over 21%for flexible IPSCs with enhanced operational stability.

Chlorine-Substituent Regulation in Dopant-Free Small-Molecule Hole-Transport Materials Improves the Effi ciency and Stability of Inverted Perovskite Solar Cells

Although doped hole-transport materials(HTMs)off er an effi ciency benefi t for perovskite solar cells(PSCs),they inevi-tably diminish the stability.Here,we describe the use of various chlorinated small molecules,specifi cally fl uorenone-triphenylamine(FO-TPA)-x-Cl[x=para,meta,and ortho(p,m,and o)],with diff erent chlorine-substituent positions,as dopant-free HTMs for PSCs.These chlorinated molecules feature a symmetrical donor-acceptor-donor structure and ideal intramolecular charge transfer properties,allowing for self-doping and the establishment of built-in potentials for improving charge extraction.Highly effi cient hole-transfer interfaces are constructed between perovskites and these HTMs by strategi-cally modifying the chlorine substitution.Thus,the chlorinated HTM-derived inverted PSCs exhibited superior effi ciencies and air stabilities.Importantly,the dopant-free HTM FO-TPA-o-Cl not only attains a power conversion effi ciency of 20.82% but also demonstrates exceptional stability,retaining 93.8%of its initial effi ciency even after a 30-day aging test conducted under ambient air conditions in PSCs without encapsulation.These fi ndings underscore the critical role of chlorine-substituent regulation in HTMs in ensuring the formation and maintenance of effi cient and stable PSCs.

High-Performance and Large-Area Inverted Perovskite Solar Cells Based on NiO_(x) Films Enabled with A Novel Microstructure-Control Technology

The improvement in the efficiency of inverted perovskite solar cells(PSCs)is significantly limited by undesirable contact at the NiO_(x)/perovskite interface.In this study,a novel microstructure-control technology is proposed for fabrication of porous NiO_(x)films using Pluronic P123 as the structure-directing agent and acetylacetone(AcAc)as the coordination agent.The synthesized porous NiO_(x)films enhanced the hole extraction efficiency and reduced recombination defects at the NiO_(x)/perovskite interface.Consequently,without any modification,the power conversion efficiency(PCE)of the PSC with MAPbl_(3)as the absorber layer improved from 16.50%to 19.08%.Moreover,the PCE of the device composed of perovskite Cs0.05(MA_(0.15)FA_(0.85))_(0.95)Pb(I_(0.85)Br_(0.15))_(3)improved from 17.49%to 21.42%.Furthermore,the application of the fabricated porous NiO_(x)on fluorine-doped tin oxide(FTO)substrates enabled the fabrication of large-area PSCs(1.2 cm^(2))with a PCE of 19.63%.This study provides a novel strategy for improving the contact at the NiO_(x)/perovskite interface for the fabrication of high-performance large-area perovskite solar cells.

High-Performance Inverted Perovskite Solar Cells with Sol-Gel-Processed Sliver-Doped NiO_(x)Hole Transporting Layer

Nickel oxide(NiO_(x))has been established as a highly efficient and stable holetransporting layer(HTL)in perovskite solar cells(PSCs).However,existing deposition methods for NiO_(x)have been restricted by high-vacuum processes and fail to address the energy level mismatch at the NiO_(x)/perovskite interface,which has impeded the development of PSCs.Accordingly,we explored the application of NiO_(x)as a hybrid HTL through a sol-gel process,where a NiO_(x)film was pre-doped with Ag ions,forming a p/p^(+)homojunction in the NiO_(x)-based inverted PSCs.This innovative approach offers two synergistic advantages,including the enlargement of the built-in electric field for facilitating charge separation,optimizing energy level alignment,and charge transfer efficiency at the interface between the perovskite and HTL.Incorporating this hybrid HTL featuring the p/p^(+)homojunction in the inverted PSCs resulted in a high-power conversion efficiency(PCE)of up to 19.25%,significantly narrowing the efficiency gap compared to traditional n-i-p devices.Furthermore,this innovative strategy for the HTL enhanced the environmental stability to 30 days,maintaining 90%of the initial efficiency.

Efficient and Stable Inverted Perovskite Solar Modules Enabled by Solid-Liquid Two-Step Film Formation

A considerable efficiency gap exists between large-area perovskite solar modules and small-area perovskite solar cells.The control of forming uniform and large-area film and perovskite crystallization is still the main obstacle restricting the efficiency of PSMs.In this work,we adopted a solid-liquid two-step film formation technique,which involved the evaporation of a lead iodide film and blade coating of an organic ammonium halide solution to prepare perovskite films.This method possesses the advantages of integrating vapor deposition and solution methods,which could apply to substrates with different roughness and avoid using toxic solvents to achieve a more uniform,large-area perovskite film.Furthermore,modification of the NiO_(x)/perovskite buried interface and introduction of Urea additives were utilized to reduce interface recombination and regulate perovskite crystallization.As a result,a large-area perovskite film possessing larger grains,fewer pinholes,and reduced defects could be achieved.The inverted PSM with an active area of 61.56 cm^(2)(10×10 cm^(2)substrate)achieved a champion power conversion efficiency of 20.56%and significantly improved stability.This method suggests an innovative approach to resolving the uniformity issue associated with large-area film fabrication.

Effective Surface Treatment for High‑Performance Inverted CsPbI2Br Perovskite Solar Cells with Efficiency of 15.92%

Developing high-efficiency and stable inverted CsPbI2Br perovskite solar cells is vitally urgent for their unique advantages of removing adverse dopants and compatible process with tandem cells in comparison with the regular.However,relatively low opening circuit voltage(Voc)and limited moisture stability have lagged their progress far from the regular.Here,we propose an effective surface treatment strategy with high-temperature FABr treatment to address these issues.The induced ions exchange can not only adjust energy level,but also gift effective passivation.Meanwhile,the gradient distribution of FA+can accelerate the carriers transport to further suppress bulk recombination.Besides,the Br-rich surface and FA+substitution can isolate moisture erosions.As a result,the optimized devices show champion efficiency of 15.92%with Voc of 1.223 V.In addition,the tolerance of humidity and operation get significant promotion:maintaining 91.7%efficiency after aged at RH 20%ambient condition for 1300 h and 81.8%via maximum power point tracking at 45°C for 500 h in N2.Furthermore,the unpackaged devices realize the rare reported air operational stability and,respectively,remain almost efficiency(98.9%)after operated under RH 35%for 600 min and 91.2%under RH 50%for 300 min.

Tin dioxide buffer layer-assisted efficiency and stability of wide-bandgap inverted perovskite solar cells

Inverted perovskite solar cells(IPSCs) have attracted tremendous research interest in recent years due to their applications in perovskite/silicon tandem solar cells. However, further performance improvements and long-term stability issues are the main obstacles that deeply hinder the development of devices. Herein, we demonstrate a facile atomic layer deposition(ALD) processed tin dioxide(SnO2) as an additional buffer layer for efficient and stable wide-bandgap IPSCs. The additional buffer layer increases the shunt resistance and reduces the reverse current saturation density, resulting in the enhancement of efficiency from 19.23% to 21.13%. The target device with a bandgap of 1.63 eV obtains open-circuit voltage of 1.19 V, short circuit current density of 21.86 mA/cm^(2), and fill factor of 81.07%. More importantly, the compact and stable SnO_(2) film invests the IPSCs with superhydrophobicity, thus significantly enhancing the moisture resistance. Eventually, the target device can maintain 90% of its initial efficiency after 600 h storage in ambient conditions with relative humidity of 20%–40% without encapsulation. The ALD-processed SnO_(2) provides a promising way to boost the efficiency and stability of IPSCs, and a great potential for perovskite-based tandem solar cells in the near future.

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.

Propylamine hydrobromide passivated tin-based perovskites to efficient solar cells

The development of tin-based devices with low toxicity is critical for the commercial viability of perovskite solar cells.However because tin halide is a stronger Lewis acid,its crystallization rate is extremely fast,resulting in the formation of numerous defects that affect the device performance of tin-based perovskite solar cells.Herein,propylamine hydrobromide(PABr)was added to the perovskite precursor solution as an additive to passivate defects and fabricate more uniform and dense perovskite films.Because propylamine cations are too large to enter the perovskite lattices,they only exist at the grain boundary to passivate surface defects and promote crystal growth in a preferred orientation.The PABr additive raises the average short-circuit current density from 19.45 to 25.47 mA·cm^(-2)by reducing carrier recombination induced by defects.Furthermore,the device’s long-term illumination stability is improved after optimization,and the hysteresis effect is negligible.The addition of PABr results in a power conversion efficiency of 9.35%.

Spatial configuration engineering of perylenediimide-based non-fullerene electron transport materials for efficient inverted perovskite solar cells

Due to their excellent photoelectron chemical properties and suitable energy level alignment with perovskite,perylene diimide(PDI)derivatives are competitive non-fullerene electron transport material(ETM)candidates for perovskite solar cells(PSCs).However,the conjugated rigid plane structure of PDI units result in PDI-based ETMs tending to form large aggregates,limiting their application and photovoltaic performance.In this study,to restrict aggregation and further enhance the photovoltaic performance of PDI-type ETMs,two PDI-based ETMs,termed PDO-PDI2(dimer)and PDO-PDI3(trimer),were constructed by introducing a phenothiazine 5,5-dioxide(PDO)core building block.The research manifests that the optoelectronic properties and film formation property of PDO-PDI2 and PDO-PDI3 were deeply affected by the molecular spatial configuration.Applied in PSCs,PDO-PDI3 with threedimensional spiral molecular structure,exhibits superior electron extraction and transport properties,further achieving the best PCE of 18.72%and maintaining 93%of its initial efficiency after a 720-h aging test under ambient conditions.

Ecofriendly Hydroxyalkyl Cellulose Additives for Efficient and Stable MAPbI_(3)-Based Inverted Perovskite Solar Cells

Perovskite solar cells(PSCs)have been demonstrated to be one of the most promising technologies in the field of renewable energy.However,the presence of the defects in the perovskite films greatly limits the efficiency and the stability of the PSCs.The additive engineering is one of the most effective approaches to overcome this problem.Most of the successful additives are extracted from the petroleum-based materials,while the research on the biomass-based additives is still lagging behind.In this paper,two ecofriendly hydroxyalkyl cellulose additives,i.e.,hydroxyethyl cellulose(HEC)and hydroxylpropyl cellulose(HPC),are investigated on the performance of the MAPbl_(3)-based inverted PSCs.Due to the strong interaction between the hydroxyl groups of the cellulose and the divalent cations of the perovskite,these additives enhance the crystal grain orientation and significantly repair the defects of the perovskite films.Working as the additives,these two cellulose derivatives show a strong passivation ability,which significantly reduces the trap density and improves the optoelectronic feature of the PSCs.Compared with the average power conversion efficiency(PCE)of the control device(19.19%),an enhancement of~10%is achieved after the addition of HEC.The optimized device(PCE=21.25%)with a long-term stability(10:80 h,PCE=20.93%)is achieved by the incorporation of the HEC additives into the precursor solution.It is the best performance among the PSCs with the cellulose additives up to now.This research provides a novel choice to develop a cost-effective and renewable additive for the PSCs with high efficiency and excellent long-term stability.

Thermally Evaporated ZnSe for Efficient and Stable Regular/Inverted Perovskite Solar Cells by Enhanced Electron Extraction

Electron transport layers(ETLs)are crucial for achieving efficient and stable planar perovskite solar cells(PSCs).Reports on versatile inorganic ETLs using a simple film fabrication method and applicability for both low-cost planar regular and inverted PSCs with excellent efficiencies(>22%)and high stability are very limited.Herein,we employ a novel inorganic ZnSe as ETL for both regular and inverted PSCs to improve the efficiency and stability using a simple thermal evaporation method.The TiO_(2)-ZnSe-FAPbl_(3)heterojunction could be formed,resulting in an improved charge collection and a decreased carrier recombination further proved through theoretical calculations.The optimized regular PSCs based on TiO_(2)/ZnSe have achieved 23.25%efficiency with negligible hysteresis.In addition,the ZnSe ETL can also effectively replace the unstable bathocuproine(BCP)in inverted PSCs.Consequently,the ZnSe-based inverted device realizes a champion efficiency of 22.54%.Moreover,the regular device comprising the TiO_(2)/ZnSe layers retains 92%of its initial PCE after 10:00 h under 1 Sun continuous illumination and the inverted device comprising the C_(60)/ZnSe layers maintains over 85%of its initial PCE at 85℃for 10:00 h.This highlights one of the best results among universal ETLs in both regular and inverted perovskite photovoltaics.

Interfacial engineering in lead-free tin-based perovskite solar cells

Lead(Pb)-free Tin(Sn)-based perovskite solar cells(PSCs)have been favored by the community due to their low toxicity,preferable bandgaps,and great potential to achieve high power conversion efficiencies(PCEs).Interfaces engineering plays important roles in developing highly efficient Sn-based PSCs via passivation of trap defects,alignment of energy levels,and incorporation of low-dimensional Sn-based perovskites.In this review,we summarize the development of Pb-free Sn-based perovskites and their applications in devices,especially the strategies of improving the interfaces.We also provide perspectives for future research.Our aim is to help the development of new and advanced approaches to achieving high-performance environment-friendly Pb-free Sn-based PSCs.

Multiple methoxy-substituted hole transporter for inverted perovskite solar cells

Inverted organic-inorganic hybrid perovskite solar cells(i-PSC)with low temperature processed interlayers and weak hysteresis behaviors have shown great potential for commercialization[1-5].However,their relatively lower power conversion efficiency(PCE)and inferior reproducibility than conventional PSCs limit further developments.These problems are largely determined by the hole transporting layer(HTL)and the quality of the upper perovskite film[6-8];in particular,the latter is considerably influenced by the surface property of the underlying HTL.

Improved interfacial property by small molecule ethanediamine for high performance inverted planar perovskite solar cells

We report a simple and effective method to realize desirable interfacial property for inverted planar perovskite solar cells(PSCs)by using small molecule ethanediamine for the construction of a novel polyelectrolyte hole transport material(P3CT-ED HTM).It is found that P3CT-ED can not only improve the hole transport property of P3CT-K but also improve the crystallinity of adjacent perovskite film.In addition,the introduction of ethanediamine into P3CT realigns the conduction and valence bands upwards,passivates surface defects and reduces nonradiative recombination.As a consequence,compared to P3CT-K hole transport layer(HTL)based devices,the average power conversion efficiency(PCE)is boosted from17.2% to 19.6% for the counterparts with P3CT-ED,with simultaneous enhancement in open circuit voltage and fill factor.The resultant device displays a champion PCE of 20.5% with negligible hysteresis.

Enhanced Photovoltage for Inverted Perovskite Solar Cells Using Delafossite CuCrO_(2) Hole Transport Material

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)has been widely adopted as hole transport material(HTM)in inverted perovskite solar cells(PSCs),due to high optical transparency,good mechanical flexibility,and high thermal stability;however,its acidity and hygroscopicity inevitably hamper the long-term stability of the PSCs and its energy level does not match well with perovskite materials with a relatively low open-circuit voltage.In this work,p-type delafossite CuCrO_(2)nanoparticles synthesized through hydrothermal method was employed as an alternative HTM for triple cation perovskite[(FAPbI_(3))_(0.87)(MAPbBr_(3))_(0.13)]_(0.92)(CsPbI_(3))_(0.08)(possessing better photovoltaic performance and stability than conventional CH3NH3PbI3)based inverted PSCs.The average open-circuit voltage of PSCs increases from 908 mV of the devices with PEDOT:PSS HTM to 1020 m V of the devices with CuCrO_(2)HTM.Ultraviolet photoemission spectroscopy demonstrates the energy band alignment between CuCrO_(2)and perovskite is better than that between PEDOT:PSS and perovskite,the electrochemical impedance spectroscopy indicates CuCrO_(2)-based PSCs exhibit larger recombination resistance and longer charge carrier lifetime than PEDOT:PSS-based PSCs,which contributes to the high VOCof CuCrO_(2)HTM-based PSCs.

Potassium thiocyanate additive for PEDOT:PSS layer to fabricate efficient tin-based perovskite solar cells

The commercialized poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)is usually used as hole transport layers(HTLs)in tin-based perovskite solar cells(TPSCs).However,the further development has been restricted due to the acidity that could damage the stability of TPSCs.Although the PEDOT:PSS solution can be diluted by water to decrease acidity and reduce the cost of device fabrication,the electrical conductivity will decrease obviously in diluted PEDOT:PSS solution.Herein,potassium thiocyanate(KSCN)is selected to regulate the properties of PEDOT:PSS HTLs from the diluted PEDOT:PSS aqueous solution by water with a volume ratio of 1:1 to prepare efficient TPSCs.The effect of KSCN addition on the structure and photoelectrical properties of PEDOT:PSS HTLs and TPSCs have been systematically studied.At the optimal KSCN concentration,the TPSCs based on KSCN-doped PEDOT:PSS HTLs(KSCN-PSCs)demonstrate the champion power conversion efficiency(PCE)of 8.39%,while the reference TPSCs only show a champioan PCE of 6.70%.The further analysis demonstrates that the KSCN additive increases the electrical conductivity of HTLs prepared by the diluted PEDOT:PSS solution,improves the microstructure of perovskite film,and inhibits carrier recombination in TPSCs,leading to the reduced hysteresis effect and enhanced PCE in KSCN-PSCs.This work gives a low-cost and practical strategy to develop a high-quality PEDOT:PSS HTLs from diluted PEDOT:PSS aqueous solution for efficient TPSCs.