Interfacial Loss Research Articles

Superb improvement of boron doping in selective emitter for TOPCon solar cells via boron-doped silicon paste

High concentration and deep p++/n junctions formed by selective boron (B)-doping can effectively reduce interfacial recombination losses and contact resistance at the emitter-metal interface of N-type TOPCon solar cells. In this work, ball milling method and thermal annealing process were adopted to realize the controllable doping of B into Si nanoparticles (NPs). By adjusting the ball milling conditions, two kinds of B-doped Si pastes were successfully prepared using B-doped Si NPs and an organic carrier. According to the simulation results and doping performance of B-doped Si paste, a suitable localized B concentration of p++/n junction was fabricated by the selected thermal diffusion process using screen printing B-doped Si paste onto the Si wafer. The maximum B-doping concentrations of p+ and p++ layers were 1.67 × 1019 and 4.91 × 1019 atoms/cm3 respectively. The depth of p+/n and p++/n junctions was 0.41 and 0.72 μm, respectively. This technology is expected to boost the power conversion efficiency of TOPCon solar cells.

Heterogeneous Cu9S5/C nanocomposite fibers with adjustable electromagnetic parameters for efficient electromagnetic absorption

One-dimensional carbon-based materials have emerged as promising electromagnetic wave absorption agents due to their outstanding conductivity, high stability, low weight, and easy availability. Properly optimizing their electromagnetic parameters is expected to further enhance the electromagnetic wave attenuation capacity. In this work, efficient Cu9S5/C nanocomposite fibers are prepared by a combined approach of electrospinning and subsequent carbonization-sulfurization processes. The Cu9S5 nanoparticles with size of ca. 100–200 nm were homogeneously embedded in fibrous carbon matrix with diameter of 300 nm. For electromagnetic wave absorption, the optimized composited nanofibers (Cu9S5/C-3) exhibited an extremely superb reflection loss of −65.4 dB (9.5 GHz, 2.7 mm) at a lower mass fraction (20 wt%). And the effective absorption bandwidth could be up to 4.1 GHz (8.0–12.1 GHz) with a matching thickness of 2.9 mm, covering the whole X-band. Electromagnetic wave attenuation mechanism investigation revealed that the performance enhancement originated from the synergy of various loss pathways, including interfacial polarization, dipole polarization, and conductive loss. The unique hierarchical structure from particle embedding, one-dimensional fiber, to three-dimensional network further amplified the performance advantages of each component. This work is anticipated to provide a feasible strategy to synthesize sulfide/carbon binary composite fibers for efficient electromagnetic wave absorption.

(Invited) Understanding the Evolution of Materials and Interfaces in Solid-State Batteries

Solid-state batteries offer improved energy density and better safety characteristics compared to lithium-ion batteries, but interfacial evolution and chemo-mechanical degradation can limit performance. In this talk, I will present my group’s recent work using in situ and operando experiments to understand nanoscale-to-macroscale evolution of materials and interfaces in solid-state batteries. Operando X-ray tomography experiments of solid-state batteries with lithium metal anodes are shown to enable real-time quantification of interfacial contact loss between lithium metal and a solid electrolyte during cycling, which is found to cause current constriction and cell failure. Deposition/stripping behavior in lithium-based batteries is also investigated in real time. Further studies reveal chemical transformations at the interface between lithium and solid electrolytes that lead to the growth of an “interphase”, which is shown to induce large stresses and to cause fracture of the solid electrolyte. Finally, reaction mechanisms in alloy-based anode materials within solid-state batteries are probed with in situ stack pressure measurements. Together, these findings show the controlling impact of the evolution of the structure, chemistry, and mechanics of the materials within solid-state batteries, with in situ and operando experiments being critical for understanding these processes.

Improveament of multiple attenuation and optimized impedance gradient for excellent multilayer microwave absorbers derived from two-dimensional metal–organic frameworks

Low-dimensional carbon matrix magnetic nanocomposites exhibit expansive prospects as lightweight microwave absorbers due to their large specific surface area and multiple attenuation characteristics. The two-dimensional (2D) flaky MOF-derived porous nanocomposites are synthesized successfully by acid etching and subsequent thermal reduction. An in-depth study of composition and flaky porous structure shows that acid etching increases multiple interfaces and carbon defects, proving beneficial for improving multiple interfacial polarization and relaxation polarization loss. In addition, the generated ferromagnetic products (Ni4N, CoFe) are beneficial in improving the magnetic loss ability. More importantly, the multilayer impedance gradient design optimizes the impedance matching characteristic. As a result, the prepared bilayer absorbing coating exhibits excellent microwave absorption properties with an effective absorption bandwidth (EAB) of 6.32 GHz at a thickness of 2.5 mm with a filling amount less than 15 wt%. When the total thickness is 3 mm, it can exhibit the widest EAB of about 7.1 GHz and the minimum reflection loss (RLmin) value of about −54.5 dB. The RCS simulation shows that the multilayer coatings exhibit good microwave scattering and absorption ability under different pitching angles, proving potential candidates for excellent microwave absorbers.

Bottom-up holistic carrier management strategy induced synergistically by multiple chemical bonds to minimize energy losses for efficient and stable perovskite solar cells

The defects from electron transport layer, perovskite layer and their interface would result in carrier nonradiative recombination losses. Poor buried interfacial contact is detrimental to charge extraction and device stability. Here, we report a bottom-up holistic carrier management strategy induced synergistically by multiple chemical bonds to minimize bulk and interfacial energy losses for high-performance perovskite photovoltaics. 4-trifluoromethyl-benzamidine hydrochloride (TBHCl) containing –CF3, amidine cation and Cl− is in advance incorporated into SnO2 colloid solution to realize bottom-up modification. The synergistic effect of multiple functional groups and multiple-bond-induced chemical interaction are revealed theoretically and experimentally. F and Cl− can passivate oxygen vacancy and/or undercoordinated Sn4+ defects by coordinating with Sn4+. The F can suppress cation migration and modulate crystallization via hydrogen bond with FA+, and can passivate lead defects by coordinating with Pb2+. The –NH2–CNH2+ and Cl− can passivate cation and anion vacancy defects through ionic bonds with perovskites, respectively. Through TBHCl modification, the suppression of agglomeration of SnO2 nanoparticles, bulk and interfacial defect passivation, and release of tensile strains of perovskite films are demonstrated, which resulted in a PCE enhancement from 21.28% to 23.40% and improved stability. With post-treatment, the efficiency is further improved to 23.63%.

Rational Design of Yolk Core-Shell Structure MnO-Co@C Nanospheres for High-Performance Microwave Absorption

MnO-Co@C nanospheres were fabricated by in situ polymerizing and high-temperature carbonizing processes. This unique synthesis method does not require any template or reducing gas. The synthesized multicore-shell structure has a shell of about 500 nm and multiple nuclei of several tens of nanometers. Subsequently, extensive experiments were conducted to adjust the material composition of the nanospheres by adjusting the amount of resorcinol and formaldehyde. The results showed that the obtained material performed best when resorcinol and formaldehyde were added to 0.2 g MnCo2O4 at 0.3 g and 0.42 mL, respectively. The efficient absorption bandwidth (EAB) value reaches 3.3 GHz when the absorber thickness is 3 mm. The reflection loss (RL) is up to −23.8 dB when the frequency is at 8.6 GHz. The unique yolk core-shell structure gives the material a heterogeneous interface, and the enhanced interfacial polarization loss causes the enhanced dielectric loss. The carbon layer with microporosity also causes conduction loss and multiple reflections. The composite structure formed by metallic Co, MnO, and carbon has better impedance matching and improved microwave absorption capability.

Dual-passivation strategy on CsPbI2Br perovskite solar cells for reduced voltage deficit and enhanced stability

The notorious defects in the grain boundaries (GBs) and surfaces trigger serious nonradiative recombination and interfacial charge losses, concomitantly exacerbating the deterioration of photovoltaic performance and phase stability of CsPbI2Br perovskite solar cells. In this work, a comprehensive dual-passivation strategy enabled by formamidine salts (FADP) is developed to annihilate defects both inside the GBs and over the surface. It is shown that formamidinothiourea (FATU) additive could effectively modulate crystallization and afford to passivate both shallow-/deep-level defects at GBs, thereby endowing CsPbI2Br films with reduced lattice micro-strains and enlarged grains over 2 µm. Meanwhile, formamidinium bromine (FABr) post-treatment can efficiently heal the defective surface and realize cationic exchange with below CsPbI2Br films, forming a gradient band alignment at the CsPbI2Br/HTL interface. Profiting from ameliorated crystallization, inhibited GBs/surface charge recombination and facilitated hole transport ability, the novel FADP strategy substantially lifts the Voc from 1.22 V to 1.34 V, yielding a champion PCE of 16.74% with greatly reduced hysteresis. Coincidently, the unencapsulated FADP devices maintained 86.2% of initial PCE after aging at 25% RH for 40 days and 83.8% after 480 h aging under continuous illumination, which is pertinent to the inhibited defective region as well as Br-rich surface.

Microrod superstructure of graphene nanocages with enhanced microwave absorption performance

The carbon based microwave absorption materials are considered as new generation absorbers owing to their lightweight, thin-thickness and good electronic conductivity. The challenge to develop excellent carbon absorbers is to improve its impedance matching behavior through decreasing its skin effect. In this study, the microrod superstructure of graphene nanocages (MSGN) have been prepared via a combination method of the precipitation, CVD and etching techniques. The MSGN realizes an optimal reflection loss of − 52.45 dB and an effective absorption bandwidth of 14.64 GHz. The unique superstructure might facilitate interfacial polarization loss and improve impedance matching behavior, thus resulting in an enhanced microwave absorption performance. Besides, the Radar Cross Section (RCS) simulation shows that MSGN delivers a reduction value of 13.50 dBm2 at the detective angle of 0°, suggesting that MSGN can be an eligible absorber for actual application.

Construction of SnO2 nanoparticle cluster@PANI core-shell microspheres for efficient X-band electromagnetic wave absorption

Superior electromagnetic (EM) wave absorption properties in 8.2–12.4 GHz (X-band) can be obtained via the effective combination of polyaniline (PANI) and SnO 2 nanoparticle cluster. In this work, SnO 2 nanoparticle cluster@PANI (SnO 2 @PANI) core-shell microspheres were firstly fabricated via a hydrothermal process followed by in-situ polymerization, and the EM wave absorption properties of SnO 2 @PANI core-shell microspheres in X band were studied. The related structure and morphology analyses indicated SnO 2 @PANI core-shell microspheres were successfully synthesized with PANI coated on the surface of SnO 2 nanoparticle cluster. The minimum reflection loss (RL min ) of − 69.1 dB (thickness of 2.78 mm) and effective absorption bandwidth (EAB) covering the whole X-band (when the thickness was from 2.5 to 3.1 mm) was achieved. Remarkable EM wave absorption properties of SnO 2 @PANI core-shell microspheres were mainly attributed to the outstanding impedance matching characteristic and dielectric loss capability (conduction loss, interfacial polarization loss and dipole polarization loss). • SnO 2 @PANI core-shell micropheres have been synthesized via a hydrothermal process followed by in-situ polymerization. • The excellent reflection loss of SnO 2 @PANI core-shell micropheres is − 69.1 dB with a matching thickness of 2.78 mm. • The effective absorption bandwidth of SnO 2 @PANI core-shell micropheres could cover the whole X-band.

Preparation of CNFs/RGO/CuS Composite Materials with Porous Structure and Excellent Microwave Absorption Performance

In this study, green cellulose nanofibers-based composites were successfully prepared for efficient wide-band electromagnetic absorber to realize functional and high-value diversified utilization of cellulose nanofibers. Specifically, by the introduction of reduced graphene oxide (RGO) and flower-like copper sulfide (CuS) into CNFs used as raw material, CNFs/RGO/CuS porous composite microwave absorber were obtained. The CNFs/RGO/CuS porous composite exhibited excellent microwave absorption performance due to its unique three-dimensional porous flower-like structure and heterogeneous interface, which provided excellent impedance matching and attenuation capabilities. The fabricated CNFs/RGO/CuS composite exhibited a minimum reflection loss (RLmin) of [Formula: see text]49.71[Formula: see text]dB at 11.52 GHz and a maximum absorption bandwidth of 5.30 GHz (from 10.40 GHz to 15.70 GHz) at only 2.50[Formula: see text]mm. In addition, the scanning electron microscope (SEM) results showed that the CNFs/RGO/CuS composite had a porous microstructure. And the Brunauer–Emmett–Teller (BET) specific surface area of the CNFs/RGO/CuS composite was 326.46[Formula: see text]m2/g. Potential absorption mechanisms were proposed considering the interfacial polarization, impedance matching, and dielectric losses caused by the synergistic effects among CNFs, RGO, and CuS. This work proposed a new strategy to biomass-based functional materials, and used the natural polymer CNFs, compounded with reduced graphene oxide and copper sulfide, to achieve efficient microwave absorbing materials.

Interfacial polarization suppression of P(VDF-HFP) film through 2D montmorillonite nanosheets coating

Polymer based dielectrics with excellent high electric field withstanding capability are of great significance for enhancing the power density and payload efficiency for both electrical and electronic systems. However, polymer-metal interface is prone to defect formation, leading to the dielectric aging and the initialization of electrical breakdown failure. A facile Montmorillonite (MMT) coating is self-co-assembled on the surface of P(VDF-HFP) high-k film to form hundreds of 2D nanosheets layers to impede the charge injection over the metal-polymer interface. The MMT coating increases the breakdown strength of the P(VDF-HFP) co-polymer film from 405 to 452 MV/m. The high field conduction study reveals a highly enhanced Schottky injection barrier that blocks the charge injection from electrodes to polymer bulk, leading to significantly suppressed charge injection and conduction loss in polymer. In addition, the introduction of MMT layered coating leads to prominent suppression of interfacial polarization loss, a phenomenon known as the blocking capacitance, which would otherwise stem from the accumulated charges of polymer-metal interface, by one order of magnitude, as demonstrated by the dielectric response analysis by using the Dissado-Hill model over a broad range of temperature and frequency. The superior charge injection and interfacial polarization suppression via the application of MMT coating impart the P(VDF-HFP) co-polymer film with higher breakdown strength, and provides an effective approach to develop high performance polymer dielectrics by interfacial engineering. This work provides insights into the understanding of the enhancement mechanism of 2D coating.

Managing Challenges in Organic Photovoltaics: Properties and Roles of Donor/Acceptor Interfaces

AbstractOrganic photovoltaics (OPVs) have demonstrated increasing potential for use in large‐area, flexible, and light‐weight applications. To date, the rapid development of nonfullerene acceptors (NFAs) and their conjugated polymeric donors have increased the efficiency of OPV by over 19%. Nevertheless, OPV is still suffering from high energy loss, which primarily derives from the donor (D)/acceptor (A) interfacial charge recombination. In particular, the voltage loss occurring at the D/A interface accounts for the current bottleneck, hampering further enhancement of the OPV efficiency. In this review, the recent discovery of D/A interfacial photophysics in NFA‐based OPVs, including the comparison with its fullerene‐based counterpart, is covered. Additionally, the factors governing interfacial energy loss, such as interfacial energetics and local morphologies, which causes the trade‐off relationship between photovoltage and photocurrent in OPV are highlighted. Accordingly, the control of D/A interfacial properties to create an “ideal” interface for charge generation in OPVs is reviewed; and emphasized that the D/A interfacial modifications can serve as a powerful tool to manage the challenges in OPVs path toward future practical applications.

Quantifying Charge Carrier Recombination Losses in MAPbI3/C60 and MAPbI3/Spiro-OMeTAD with and without Bias Illumination.

To increase the open-circuit voltage in perovskite-based solar cells, recombination processes at the interface with transport layers (TLs) should be identified and reduced. We investigated the charge carrier dynamics in bilayers of methylammonium lead iodide (MAPbI3) with C60 or Spiro-OMeTAD using time-resolved microwave conductance (TRMC) measurements with and without bias illumination (BI). By modeling the results, we quantified recombination losses in bare MAPbI3 and extraction into the TLs. Only under BI did we find that the density of deep traps increases in bare MAPbI3, substantially enhancing trap-mediated losses. This reversible process is prevented in a bilayer with C60 but not with Spiro-OMeTAD. While under BI extraction rates reduce significantly in both bilayers, only in MAPbI3/Spiro-OMeTAD does interfacial recombination also increases, substantially reducing the quasi Fermi level splitting. This work demonstrates the impact of BI on charge dynamics and shows that adjusting the Fermi level of TLs is imperative to reduce interfacial recombination losses.

D-A-π-A organic dyes with fluorenyl-substituted bulky donor for efficient dye-sensitized solar cells

Improving light-harvesting efficiency and suppressing interfacial charge recombination are of paramount importance to the development of Cu (II/I) redox shuttle-based dye-sensitized solar cells (DSSCs). Here, we present a rational molecular engineering on D-A-π-A organic sensitizers featuring with fluorenyl-substituted bulky donor (HY57, HY60, and HY61) for Cu (II/I) mediated DSSCs. By gradually enhancing conjugation and rigidity of the π-spacer and auxiliary acceptor moieties, the light-harvesting and electron-injection efficiencies can be simultaneously improved. The large size of fluorenyl-substituted arylamine donor together with abundant alkyl chains decorated on the molecular structures assist dense assembly of dye monolayer at surface of nanocrystalline TiO2, which largely suppress interfacial charge recombination losses. When applied in Cu (II/I) mediated DSSCs, the combination of an auxiliary acceptor of phenanthrene-fused-quinoxaline (PFQ) and a π-spacer of cyclopentadithiophene (CPDT) in dye HY61 results in a simultaneous enhancement in short-circuit current (JSC) and open-circuit voltage (VOC), thus improving the power conversion efficiency (PCE) from 7.3% for reference dye HY59 to 10.3% for HY61. This study demonstrates that rigid and fused building block is promising towards constructing highly efficient organic sensitizers.

Reduced graphene oxide(rGO)-Ferrite composite inks and their printed meta-structures as an adaptable EMI shielding material

ABSTRACT Electromagnetic interference (EMI) shielding inks are generally conducting inks and therefore, are mostly reflection based. EMI shielding based on reflection are sometimes not suitable for certain applications apart from the fact that they themselves act as secondary source of EM waves. Here, we develop reduced graphene oxide (rGO)- zinc nickel ferrite (ZNF) and rGO-manganese (Mn)-doped zinc nickel ferrite inks for EM absorption in X-band, which have been tested in liquid state, coatings, and as printed meta-structures demonstrating versatile use of the inks. As a coating, the average EMI shielding of more than 30 dB is achieved in the 8 to 12 GHz range. The absorption properties of the rGO based ink can be increased from 50% to more than 80% by addition of a ferrite composite and can further be tuned by Mn doping. The dielectric measurement studies reveal that addition of Mn creates sites for interfacial polarization. The interfaces between polymer matrix, rGO, ZNF, and Mn contribute to conductivity, dipole and interfacial polarization losses, thereby augmenting absorption dominated EMI shielding. Cole-cole plot for the inks also indicates multiple relaxation processes confirming the role interfaces in absorption properties of the composite ink.

Optimal Solvents for Interfacial Solution Engineering of Perovskite Solar Cells

Interfacial engineering is extensively used to reduce the interfacial loss caused by surface recombination, improve the crystallinity of the active absorption layer, and enhance the long‐term stability of perovskite solar cells (PSCs). Solution processing techniques, such as spin coating and dip coating, are commonly used to deposit the interfacial layer because of their cost‐effectiveness and simplicity. Although determining suitable solutes for use in these processes is important, selecting appropriate solvents is also crucial. Herein, commonly used solvents are investigated to determine optimal solvents for solution processing by categorizing them into nonpolar and polar groups. The results suggest that the efficiency of the PSCs can be increased by simple solvent treatment. In particular, the efficiencies of systems subjected to hexane (nonpolar) and ethanol (polar) treatment are significantly improved (17.31% and 17.44%, respectively) compared with that of a control device (16.24%). Herein, the effects of pure solvents on the SnO2–perovskite interface are confirmed and an important direction for investigations that adopt solution processing to improve the efficiency of PSCs, such as research on interlayers and self‐assembled monolayers, is suggested.

Construction of heterointerfaces and honeycomb-like structure for ultrabroad microwave absorption

Heterointerface design is an effective strategy to improve the effective absorption bandwidth in electromagnetic wave EMW absorbing materials. In this paper, honeycomb-like Fe-doped tremella carbide composites (FCT) with a large number of heterogeneous interfaces were obtained by in-situ construction of multiphase composite particles (Fe3C, Fe3O4, and a-Fe) during the carbonization process. The effects of Fe doping on the phase, structure, morphology, and absorption properties of FCT were investigated. The results show that the porous structure and the heterogeneous interface can significantly improve the electromagnetic wave absorption performance of FCT. Iron doping introduces a heterogeneous multiphase structure into FCT, which increases the interfacial loss and magnetic loss of the material, thereby improving the overall impedance matching of the material. FCT-4 composite exhibited excellent microwave attenuation capability with a reflection loss of −34.6 dB. Simultaneously, the widest effective absorption bandwidth is up to 8.84 GHz (9.16–18 GHz) with a matching thickness of 2.8 mm, which covers almost the entire X (8–12 GHz) and Ku (12–18 GHz) bands. Thus, this paper provides an effective strategy for the preparation of excellent electromagnetic wave absorbing materials by in situ construction of heterointerfaces.

Influence of N-doping on dielectric properties of carbon-coated copper nanocomposites in the microwave and terahertz ranges

Carbon-coated Cu nanocomposites (Cu@C NCs) consisting of core-shell nanoparticles and nanorods were synthesized by arc discharge plasma under an atmosphere of He and H2 gas, and the N-doping of them was achieved by a post-treatment process using ureal as the precursor. The concentration of N in the N-doped samples varies in the range of 0.62%–2.31 % (in mole), with a transformation from pyrrolic N to graphitic N when increasing the relative content of ureal. Dielectric properties of the NCs without or with N-doping in the microwave and THz bands were investigated. The N-doped samples achieve the enhanced dielectric loss in both microwave and THz bands. In the microwave band, dielectric loss was dominated by interfacial polarization, dipolar polarization, and conduction loss, while in the THz band, plasma resonance, ionic polarization and conduction loss are responsible for the dielectric loss, with a strong absorption characteristic dominated by conductive effect.

Simultaneous Interfacial Modification and Defect Passivation for Wide-Bandgap Semitransparent Perovskite Solar Cells with 14.4% Power Conversion Efficiency and 38% Average Visible Transmittance.

Perovskite materials offer a great potential in the application of semitransparent solar cells, owing to the tunable bandgap, ease of preparation and excellent photovoltaic property. A majority of works exhibit high average visible-light transmittance (AVT) for semitransparent perovskite solar cells (ST-PSCs) through decreasing perovskite thickness, leading to sacrificing the power conversion efficiency (PCE) of the device. Herein, a wide-bandgap (WBG) perovskite of Cs0.2 FA0.8 Pb(I0.6 Br0.4 )3 is applied as absorber in ST-PSCs, which is a tremendous progress to balance both large PCE and high AVT. Moreover, a strategy of simultaneous interfacial modification and defect passivation is provided to enhance the performance of WBG ST-PSCs. Consequently, an inverted planar structure WBG perovskite solar cell (PSC) achieves 15.06% of PCE with excellent stability by restraining the interfacial energy loss and suppressing the nonradiative recombination. Furthermore, the ST-PSC obtains high PCE of 14.40% with an AVT of 38% by means of optimizing the transparent electrode. This work provides an efficient and simple method to improve the performance and AVT of ST-PSCs for the application in building-integrated photovoltaics.

Low-energy-consumption fabrication of porous TPU/graphene composites for high-performance microwave absorption and the influence of Fe3O4 incorporation

Fabrication of lightweight, thin thickness, broad bandwidth, strong absorption, and lower filler loading materials are of great interest for microwave absorption. Herein, porous thermoplastic polyurethane (TPU) /graphene composites were successfully prepared via a facile vapor induced phase separation (VIPS) technique. Compared with TPU foam, the introduction of graphene endows the composites favorable microwave absorption ability. The optimized composite foam with 3 wt% graphene (TPU/G-3) exhibits extraordinary wave attenuation capacity with a minimum reflection loss (RL min ) value of − 51.86 dB and effective absorption bandwidth (EAB) of 4.28 dB (12.6–17.0 GHz) at the thickness of 3.1 mm. Microwave attenuation mechanism indicates that the remarkable microwave absorption ability derives from conduction loss, dipole polarization loss, interfacial polarization loss as well as multiple scattering. Incorporating the same amount of Fe 3 O 4 as graphene to TPU/G-3 endows the composites with the RL min of − 58.96 dB, which is slightly better than TPU/G-3 due to more favorable impedance matching. However, the matching thickness becomes much higher to about 8.0 mm, which is mainly attributed to bigger pores caused by Fe 3 O 4 . Moreover, the VIPS strategy provides insight into the fabrication of facile and lightweight polymer-based porous electromagnetic absorption materials. • Vapor induced phase separation method for preparation of TPU-based porous composites. • Graphene facilitates heterogeneous nucleation for smaller pores than TPU foam. • Graphene content of 3 wt% endows composite favorable microwave absorbing performance. • Fe 3 O 4 influences the process of vapor induced phase separation with bigger pores. • Fe 3 O 4 improves the reflection loss but increases matching thickness due to big pores.