Blade-coating Perovskite Films with Diverse Compositions for Efficient Photovoltaics

In this research highlight,recent significant advances with hot-assisted blade-coating or air knife-assisted blade-coating of different perovskite compositions with bandgaps ranging from 1.3 eV to 1.9 eV(i.e.widebandgap or small-bandgap perovskites with mixed cations and anions,2D/3D perovskites,Pb/Sn binary perovskites,and all-inorganic perovskites)for single-junction or tandem PSCs are discussed,with an emphasis on elucidating the distinct ink formulation engineering strategies,crystal growth mechanisms,crystallization kinetics,and optoelectronic properties of the different perovskite compositions.

Stabilization of formamidinium lead iodide perovskite precursor solution for blade-coating efficient carbon electrode perovskite solar cells

Formamidinium lead triiodide(FAPbI_(3))is a research hotspot in perovskite photovoltaics due to its broad light absorption and proper thermal stability.However,quite a few researches focused on the stability of the FAPbI_(3) perovskite precursor solutions.Besides,the most efficient FAPbI_(3) layers are prepared by the spin-coating method,which is limited to the size of the device.Herein,the stability of FAPbI_(3) perovskite solution with methylammonium chloride(MACl)or cesium chloride(CsCl)additive is studied for preparing perovskite film through an upscalable blade-coating method.Each additive works well for achieving a high-quality FAPbI_(3) film,resulting in efficient carbon electrode perovskite solar cells(pero-SCs)in the ambient condition.However,the perovskite solution with MACl additive shows poor aging stability that noα-FAPbI_(3) phase is observed when the solution is aged over one week.While the perovskite solution with CsCl additive shows promising aging stability that it still forms high-quality pureα-FAPbI_(3) perovskite film even the solution is aged over one month.During the solution aging process,the MACl could be decomposed into methylamine which will form some unfavored intermediated phase inducingδ-phase FAPbI_(3).Whereas,replacing MACl with CsCl could effectively solve this issue.Our founding shows that there is a great need to develop a non-MACl FAPbI_(3) perovskite precursor solution for cost-effective preparation of pero-SCs.

Development and application of blade-coating technique in organic solar cells

Due to the characteristics of lower material waste,higher crystallinity,roll-to-roll compatibility,and high-throughput continuous processing,blade-coating has been widely applied in the preparation of large-area organic solar cells.In this paper,the technique of blade-coating is introduced,including the effects of blading speed,substrate temperature,and other technological innovations during the process of blade-coating.Besides,the recent progress of blade-coating in organic solar cells is summarized and the active layer prepared by a blade-coating method is introduced in detail,including materials,processing methods,solvents,and additives.The interface layer and electrodes prepared by the blade-coating method are also discussed.Finally,some perspectives on the blade-coating method are proposed.In the foreseeable future,blade-coating will become the core of batch production of large-area organic solar cells,so as to make organic solar cells more competitive.

Green‑Solvent Processed Blade‑Coating Organic Solar Cells with an Efficiency Approaching 19%Enabled by Alkyl‑Tailored Acceptors

Power-conversion-efficiencies(PCEs)of organic solar cells(OSCs)in laboratory,normally processed by spin-coating technology with toxic halogenated solvents,have reached over 19%.However,there is usually a marked PCE drop when the bladecoating and/or green-solvents toward large-scale printing are used instead,which hampers the practical development of OSCs.Here,a new series of N-alkyl-tailored small molecule acceptors named YR-SeNF with a same molecular main backbone are developed by combining selenium-fused central-core and naphthalene-fused endgroup.Thanks to the N-alkyl engineering,NIR-absorbing YR-SeNF series show different crystallinity,packing patterns,and miscibility with polymeric donor.The studies exhibit that the molecular packing,crystallinity,and vertical distribution of active layer morphologies are well optimized by introducing newly designed guest acceptor associated with tailored N-alkyl chains,providing the improved charge transfer dynamics and stability for the PM6:L8-BO:YRSeNF-based OSCs.As a result,a record-high PCE approaching 19%is achieved in the blade-coating OSCs fabricated from a greensolvent o-xylene with high-boiling point.Notably,ternary OSCs offer robust operating stability under maximum-power-point tracking and well-keep>80%of the initial PCEs for even over 400 h.Our alkyl-tailored guest acceptor strategy provides a unique approach to develop green-solvent and blade-coating processed high-efficiency and operating stable OSCs,which paves a way for industrial development.

Long-Chain Gemini Surfactant-Assisted Blade Coating Enables Large-Area Carbon-Based Perovskite Solar Modules with Record Performance

Carbon-based perovskite solar cells show great potential owing to their low-cost production and superior stability in ambient air.However,scaling up to high-efficiency carbon-based solar modules hinges on reliable deposition of uniform defect-free perovskite films over large areas,which is an unsettled but urgent issue.In this work,a long-chain gemini surfactant is introduced into perovskite precursor ink to enforce self-assembly into a network structure,considerably enhancing the coverage and smoothness of the perovskite films.The long gemini surfactant plays a distinctively synergistic role in perovskite film construction,crystallization kinetics modulation and defect passivation,leading to a certified record power conversion efficiency of 15.46%with Voc of 1.13 V and Jsc of 22.92 mA cm^(-2)for this type of modules.Importantly,all of the functional layers of the module are printed through a simple and high-speed(300 cm min^(-1))blade coating strategy in ambient atmosphere.These results mark a significant step toward the commercialization of all-printable carbon-based perovskite solar modules.

Improvement on the performance of perovskite solar cells by doctor-blade coating under ambient condition with hole-transporting material optimization

Numerous fabrication methods have been developed for high-efficiency perovskite solar cells(PSCs). However, these are limited to spin-coating processes in a glove box and are yet to be commercialized. Therefore, there is a need to develop a controllable and scalable deposition technique that can be carried out under ambient conditions. Even though the doctor-blade coating technique has been widely used to prepare PSCs, it is yet to be applied to high-efficiency PSCs under ambient conditions(RH ~45%, RT ~25 °C). In this study, we conducted blade-coating fabrication of modified high-efficiency PSCs under such conditions. We controlled the substrate temperature to ensure phase transition of perovskite and added dimethyl sulfoxide(DMSO) to the perovskite precursor solution to delay crystallization, which can facilitate the formation of uniform perovskite films by doctor-blade coating. The as-prepared perovskite films had large crystal domains measuring up to 100 μm. Solar cells prepared from these films exhibited a current density that was enhanced from 17.22 to 19.98 m A/cm^2 and an efficiency that was increased from 10.98% to 13.83%. However, the open-circuit voltage was only 0.908 V, probably due to issues with the hole-transporting layer. Subsequently, we replaced poly(3,4-ethylenedioxythiophene) polystyrene sulfonate(PEDOT:PSS) with Ni O x as the hole-transporting material and then prepared higher-quality perovskite films by blade-coating under ambient conditions. The as-prepared perovskite films were preferably orientated and had large crystal domains measuring up to 200 μm;The open-circuit voltage of the resulting PSCs was enhanced from 0.908 to 1.123 V, while the efficiency increased from 13.83% to 15.34%.

Non-conjugated terpolymer acceptors for highly efficient and stable lager-area all-polymer solar cells

All-polymer solar cells(all-PSCs)have made significant progress recently,but few studies have been conducted to investigate the lab-to-manufacturing translation from the spin-coating method to the printing process.Here,the random copolymerization method and non-conjugated backbone approach are integrated to manipulate the morphology and photoelectric properties of the active layer for large-area printed all-PSCs.A series of non-conjugated terpolymer acceptors PYSe-TC_(6)T(x)(x=5,10,and 20,refers to the molar ratio of TC_(6)T unit)are developed by covalently introducing non-conjugated unit TC_(6)T into the PYSe host bipolymer by random copolymerization.The spin-coated PYSe-TC_(6)T(10)-based all-PSC demonstrates the best power conversion efficiency(PCE)of 13.54%,superior to the PYSe-based one(12.45%).More intriguingly,morphological studies reveal that a combination of the random polymerization and non-conjugated backbone strategy can effectively prevent the active layer from overaggregation and improve the film quality during the printing process,thereby minimizing the efficiency and technology gap between spin-coated small-area devices and blade-coated large-area devices.By directly using the same preparation condition of spin-coating,the blade-coated small-area(0.04 cm^(2))delivers a PCE of 12.83%and the large-area(1.21 cm^(2))device achieves a PCE of 11.96%with a small PCE loss.Both PCE value and PCE loss are one of the most outstanding performances of the bladecoated all-PSCs.These findings reveal that a combination of the non-conjugated flexible backbone with random copolymerization to develop non-conjugated terpolymers is an attractive design concept to smoothly realize the lab-to-manufacturing translation.

Self-assembled monolayer enabling improved buried interfaces in blade-coated perovskite solar cells for high efficiency and stability

Despite the rapidly increased power conversion efficiency(PCE)of perovskite solar cells(PVSCs),it is still quite challenging to bring such promising photovoltaic technology to commercialization.One of the challenges is the upscaling from small-sized lab devices to large-scale modules or panels for production.Currently,most of the efficient inverted PVSCs are fabricated on top of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine](PTAA),which is a commonly used hole-transporting material,using spin-coating method to be incompatible with large-scale film deposition.Therefore,it is important to develop proper coating methods such as blade-coating or slot-die coating that can be compatible for producing large-area,high-quality perovskite thin films.It is found that due to the poor wettability of PTAA,the blade-coated perovskite films on PTAA surface are often inhomogeneous with large number of voids at the buried interface of the perovskite layer.To solve this problem,self-assembled monolayer(SAM)-based hole-extraction layer(HEL)with tunable headgroups on top of the SAM can be modified to provide better wettability and facilitate better interactions with the perovskite coated on top to passivate the interfacial defects.The more hydrophilic SAM surface can also facilitate the nucleation and growth of perovskite films fabricated by blade-coating methods,forming a compact and uniform buried interface.In addition,the SAM molecules can also be modified so their highest occupied molecular orbital(HOMO)levels can have a better energy alignment with the valence band maxima(VBM)of perovskite.Benefitted by the high-quality buried interface of perovskite on SAM-based substrate,the champion device shows a PCE of 18.47%and 14.64%for the devices with active areas of 0.105 cm^(2) and 1.008 cm^(2),respectively.In addition,the SAM-based device exhibits decent stability,which can maintain 90%of its initial efficiency after continuous operation for over 500 h at 40℃ in inert atmosphere.Moreover,the SAM-based perovskite mini-module exhibits a PCE of 14.13%with an aperture area of 18.0 cm^(2).This work demonstrates the great potential of using SAMs as efficient HELs for upscaling PVSCs and producing high-quality buried interface for large-area perovskite films.

Silver nanowire/polymer composite soft conductive film fabricated by large-area compatible coating for flexible pressure sensor array

Soft conductive films composed of a silver nanowire(AgNW) network, a neutral-pH PEDOT:PSS overcoating layer and a polydimethylsiloxane(PDMS) elastomer substrate are fabricated by large area compatible coating processes. The neutral-pH PEDOT:PSS layer is shown to be able to significantly improve the conductivity,stretchability and air stability of the conductive films. The soft conductive films are patterned using a simple maskless patterning approach to fabricate an 8 x 8 flexible pressure sensor array. It is shown that such soft conductive films can help to improve the sensitivity and reduce the signal crosstalk over the pressure sensor array.