Polyurethane Films Research Articles

A highly reactive soybean oil-based superhydrophobic polyurethane film with long-lasting antifouling and abrasion resistance.

Superhydrophobic polyurethanes offer robust hydrophobicity and corrosion resistance. However, it is essential to consider the durability and environmental constraints associated with these materials. This study prepared a bio-based superhydrophobic polyurethane coating film using epoxidized soybean oil, superhydrophobically modified silica nanoparticles, and OH-PDMS-OH as surface modifiers. The coating film exhibited sustained super-hydrophobicity and an excellent antifouling effect for pu-erh tea and edible oils, among other substances, after 14 days of immersion in solutions with different pH values, 28 days of exposure to air, and 2000 abrasion cycles. This finding can be applied to the development of daily indoor and outdoor antifouling protective coatings and provides a new method for the preparation of green and durable superhydrophobic antifouling coating films.

Textured anti-reflection and down-conversion composite functional films for high-efficiency solar cells.

Advances in high-efficiency solar cells introduce photon management challenges, including the difficult texturization of flat surfaces and low photon utilization at short wavelengths. While bifacial crystalline silicon solar cells have a front pyramid structure and SiN x layers reduce reflections, managing photons on the flat backside remains a challenge. To enhance light utilization, a soft nanoimprint technique was utilized to create pyramid micro-structured polyurethane films doped with europium (Eu3+) complex. These films, which possess anti-reflection and down-conversion properties, can be applied externally to various high-efficiency solar cells without compromising electrical performance. Research on the backside of bifacial PERC solar cells revealed that the optimal composite functional film increases the integrated current by 5.70%, with a 1.27% gain from down-conversion effects. This specialized film presents a novel approach to interface matching for different types of solar cells.

Synthesis of catalyzed polyurethane films using varying content of isocyanates, glycols, and chain extenders

Polyurethane (PU) films are regarded as an important polymeric class in coating sectors. PU exhibits various advantageous features like coatings to shield metals and wooden objects, adhesives, sealants, and elastomeric properties in a broader perspective to boost the appearance and packaging. In the medical field, PU shows bactericidal qualities for real-world uses, but efforts are required to strengthen the antibacterial characteristics in polyurethane films. The present research is intended to develop five (05) different novel polyurethane films with excellent anti-bacterial properties. Polyurethane films were prepared using isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI) as aliphatic diisocyanate, 1, 4-Butanediol (BDO) as chain extender, and Polytetra-methylene glycol-1000 (PTMG-1000) and Polytetra-methylene glycol-2000 (PTMG-2000) as glycol. The reaction was conducted in a polymerization chamber using 2,2-Dimorpholinodiethylether (DMDEE) and 4–4, bioxdimorphline as a catalyst. Surface morphology and characteristics, thermal stability, tensile and viscoelastic properties were characterized using SEM, XRD, FTIR, contact angle, TMA, tensile and rheometry testing. Furthermore, an anti-bacterial test was performed to confirm PU film usage as an occlusive dressing. FTIR results of PU films based on PTMG2000 & IPDI, PTMG1000 & IPDI, and PTMG2000 & HDI showed an increase in hydrogen bonding with the intensity of the C = O band when the NCO: OH concentration was increased. But due to incompatibility of the (OH) soft segment of glycol with the hard (NCO) segment of isocyanate caused a drop in the peak strength of PU films based on PTMG2000 & HDI and PTMG1000 & IPDI. The tensile strength is trending upward for these PU samples PTMG2000 & IPDI, PTMG1000 & IPDI, and PTMG2000 & HDI. While the PTMG2000 & HDI polyurethane sample has the highest tensile strength (105 MPa) and the lowest elongation (12.2 %) at break point. (XRD and (SEM) Results showed that the crystallinity of the synthesized polyurethane films was affected by varying the NCO: OH content and this content favored the formation of ordered structure as higher peak intensities in these PU samples PTMG2000 & IPDI, PTMG1000 & IPDI, and PTMG2000 & HDI.

CUSTO-EFETIVIDADE DE DUAS COBERTURAS NA PREVENÇÃO DE LESÃO POR PRESSÃO EM PACIENTES DE TERAPIA INTENSIVA

ABSTRACT Objective: to analyze the cost-effectiveness of using silicone adhesive multilayer foam and transparent polyurethane film in preventing pressure injuries in patients admitted to an Intensive Care Unit. Method: this is an economic cost-effectiveness study, developed with public domain data and a rapid literature review, which included three studies developed in Canada, the United Kingdom, Italy and the United States. The searches were carried out in the PubMed, Cochrane and Scopus databases. The population was patients admitted to the Intensive Care Unit. The perspective was from the Brazilian Health System, with a time horizon of less than one year. Data was collected and analyzed between March and June 2022. A decision tree model was developed using TreeAge Pro® 2017 software to project economic outcomes of incremental cost and effectiveness, incremental cost per effectiveness, and cost per percentage increase in preventing the development of pressure injuries. Sensitivity analysis was also performed. The Consolidated Health Economic Evaluation Reporting Standards and the Methodological Guideline for Economic Evaluation of the Brazilian Ministry of Health recommendations were adopted. Results: multilayer foam reduces the occurrence of pressure injuries at a lower cost when compared to film, promoting an average saving of R$ 278.78 (US$ 1,393.90) for each patient. Conclusion: multilayer foam was the most cost-effective technology in preventing pressure injuries in Intensive Care Unit patients in the Brazilian Health System.

Tetramethylpyrazine-derived polyurethane for improved hemocompatibility and rapid endothelialization.

Thrombosis and intimal hyperplasia (IH) are the main factors affecting the long-term patency of small-diameter vascular grafts (SDVGs). Fabricating a confluent endothelial cell (EC) layer on surfaces with physiological elasticity to mimic vascular endothelium should be an effective strategy to prevent restenosis that is caused by thrombosis and IH. However, the vascular endothelialization process is time-consuming and always constrained by hemocompatibility of the vascular grafts, since excellent hemocompatibility could guarantee a sufficient time window for the endothelialization process. Tetramethylpyrazine (TMP)-derived polyurethane (PU) with improved hemocompatibility and accelerated endothelialization ability is synthesized by incorporating TMP moieties into PU backbones. Results show that TMP-contained PU films possess improved hemocompatibility by down-regulating platelet adhesion/activation and increasing the clotting time. Furthermore, the in vitro human umbilical vein endothelial cell (HUVEC) test demonstrates that the introduction of TMP can significantly promote HUVEC adhesion and proliferation, and thus accelerate luminal endothelialization of vascular grafts. Moreover, the TMP-containing PU films exhibit excellent biocompatibility especially for HUVECs, and their excellent, adjustable elasticity (1123%) guarantees compliance accommodation of vascular grafts. This newly synthesized TMP-containing material with multiple biological functions is expected to make up for the shortcomings of available SDVGs in clinical practice, and has significant potential in improving the long-term patency of SDVGs.

Biodegradability Properties of Polyurethane Film Made from Eucalyptus pellita Wood Polyol

The properties of polyurethane (PU) film are greatly influenced not only by the raw materials but also by the compatibility of polyol and isocyanate. This paper aimed to evaluate the effect of the isocyanate index (NCO/OH ratio) on the biodegradability properties of Eucalyptus pellita PU film. E. pellita wood polyol and polymeric methylene diphenyl diisocyanate (pMDI) were mixed at different NCO/OH ratios (1.8 – 3.0). The PU film was produced through the one-shot method. The effect of the NCO/OH ratio on the biodegradability properties of PU film was evaluated. The rate of biodegradation of PU film by soil burial test decreases proportionally to the NCO/OH ratio. The biodegradation rate is the highest (14.02%) when the NCO/OH ratio is the lowest (1.8). The results of water solubility showed that PU films with low NCO/OH ratios are easily soluble in water. The band associated with the ester compound was detected at nearly 1,060 cm−1. Based on the findings of this study, increasing the NCO/OH ratio made the PU film from E. pellita less degradable. Therefore, lowering the NCO/OH ratio is an ideal option to produce films with better biodegradability.

Transparent, multifunctional and multiform ionic sensors prepared by one-step impregnation

Under current technology trends, wearable devices with high levels of transparency and flexibility have become hotspots to improve aesthetics or enhance security for civilian and military applications. Simultaneously, the single sensor can no longer satisfy the various needs, like temperature and humidity, stress and strain and so on. However, it is still challenging that how to fabricate multifunctional transparent sensors nowadays. In this paper, the transparent polyurethane (PU) film was easily prepared by impregnating the ionic liquid (IL) into the pure PU film (PU@IL). And the effects of film thickness, ionic concentration and fiber morphology on transparency are investigated by experiments and simulations. On the basis of it, several sensors based on PU@IL film are further developed. The resistive sensor with PU@IL film shows different sensing abilities for stress, strain and temperature. Capacitive sensor based on indium tin oxide (ITO)-PU@IL-ITO has a lower stress detection limit (0.51 kPa) and faster response/recovery time (136.8 ms/68.4 ms). This paper may provide a novel strategy to design and fabricate multifunctional and multiform sensors with good mechanical properties, transparency and wide applications (preventing scalds, monitoring physiological activities).

Grafting of Poly(N-Vinylcaprolactam) in polyurethane by gamma radiation

Poly (N-vinylcaprolactam) (PNVCL) is a thermoresponsive, biocompatible, non-toxic polymer with a phase transition temperature from hydrophilic to hydrophobic state (Tpt) close to the physiological one. This temperature is influenced by PNVCL molar mass and its copolymerization. In this work, gamma radiation at doses of 5 and 20 kGy was used to graft PNVCL chains onto films of thermoplastic polyurethane (TPU). PNVCL homopolymers were also developed by gamma radiation at the same conditions. The materials were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), viscometry and thermogravimetric analaysis (TGA). PNVCL grafting enabled thermoresponsive character to TPU films, as observed by changes in water-surface contact angles above and below Tpt. The Tpt of the developed homopolymers determined by cloud point and rheological analysis was close to 30 °C. These results demonstrated the feasibility of developing a graft copolymer with thermoresponsive properties, with the innovation of grafting PNVCL onto TPU films using gamma radiation.

Preparation and application of high sound insulation polyurethane composite film through glass fiber reinforcement

AbstractLaminated glasses have been widely used in buildings, physical protections, and vehicles because of their safety, sound insulation, thermal insulation, and other performance. In recent years, the high sound insulation performance of laminated glass intermediate films in the frequency range of low or high frequencies has attracted more and more attentions. In this work, a glass fiber/polyurethane elastomer composite (PU‐MGF) film with high transparency and impact resistance has been successfully synthesized, 5 dB of the transmission loss increased at 1600–6000 Hz, and 3.6 dB increased at 63–1600 Hz compared with the control polyurethane film. This is a significant progress in the laminated glass industry. In addition, the transmittance of the composite reaches over 75%. The excellent impact resistance of the laminated glass, based on PU‐MGF film, has been confirmed through falling ball impact test, demonstrating its ability to withstand multiple impacts without spattering. The PU‐MGF film prepared in this work exhibits great potential for applications in building windows, transportation, and soundproof devices.

Dual Ratiometric Fluorescence Monitoring of Mechanical Polymer Chain Stretching and Subsequent Strain-Induced Crystallization.

Tracking the behavior of mechanochromic molecules provides valuable insights into force transmission and associated microstructural changes in soft materials under load. Herein, we report a dual ratiometric fluorescence (FL) analysis for monitoring both mechanical polymer chain stretching and strain-induced crystallization (SIC) of polymers. SIC has recently attracted renewed attention as an effective mechanism for improving the mechanical properties of polymers. A polyurethane (PU) film incorporating a trace of a dual-emissive flapping force probe (N-FLAP, 0.008 wt %) exhibited a blue-to-green FL spectral change in a low-stress region (<20 MPa), resulting from conformational planarization of the probe in mechanically stretched polymer chains. More importantly, at higher probe concentrations (∼0.65 wt %), the PU film showed a second spectral change from green to yellow during the SIC growth (20-65 MPa) due to self-absorption of scattered FL in a short wavelength region. The reversibility of these spectral changes was demonstrated by load-unload cycles. With these results in hand, the degrees of the polymer chain stretching and the SIC were quantitatively mapped and monitored by dual ratiometric imaging based on different FL ratios (I525/I470 and I525/I600). Simultaneous analysis of these two mappings revealed a spatiotemporal gap in the distribution of the polymer chain stretching and the SIC. The combinational use of the dual-emissive force probe and the ratiometric FL imaging is a universal approach for the development of soft matter physics.

Robust integration of "top-down" strategy and triple-structure design for nature-skin derived e-skin with superior elasticity and ascendency strain and vibration sensitivity

The rapid advancement of bio-integrated electronics in recent years has been paralleled by increased interest in the research of stretchable, elastic, conductive, and multi-dimensional sensing electronic skin (e-skin) due to its potential integration with electronic devices and soft tissues. In this work, we presented the fabrication of a nature-skin derived e-skin, denoted as S-P/G@PU e-skin, achieved through an on-demand "top-down" strategy and a triple structure design, employing integrated in-situ polymerization, impregnation, and encapsulation techniques. The collagen fibers weaved hierarchical 3D structure of natural skin, was strategically employed to host conductive polypyrrole and combined with a binary solvent system of glycerin and water. Subsequently, this composite natural skin was coated with polyurethane films, resulting in the engineering of the S-P/G@PU e-skin. This innovative e-skin exhibited remarkable properties, including high tensile strength (8.76 MPa), excellent elasticity (0–180 %), anti-freezing capacity, moisture retention, substantial conductivity (6.3 S/m), and outstanding multi-dimensional sensing capabilities. Importantly, the S-P/G@PU e-skin functioned as both a slow adaptive resistance strain sensor and a fast adaptive single-electrode triboelectric nanogenerator, making it a versatile sensing system that enabled real-time monitoring of various physiological signals from the human body and wide-frequency vibration signals from devices such as cellphones and motors. This study serves as a proof of concept for transforming nature-skin into e-skin, showcasing the potential for integrated wearable electronics, artificial intelligence, and human-machine interfaces.

Hierarchically patterned polyurethane microgrooves featuring nanopillars or nanoholes for neurite elongation and alignment

Surface micro- and nanostructures profoundly affect the functional performance of nerve regeneration implants by modulating neurite responses. However, few studies have investigated the impact of discrete nanostructures, such as nanopillars and nanoholes, and their combination with microgrooves on neurite outgrowth and alignment. Furthermore, numerous techniques have been developed for surface micro-/nanopatterning, but simple and low-cost approaches are quite limited. In this work, we show that nanopillars and nanoholes, and their combination with microgrooves, can be patterned on polyurethane (PU) films using a low-cost, reusable photoresist master mold prepared via nanosphere lens lithography and UV-LED photolithography, with specific “reinforcement” methods for overcoming the inherent drawbacks of using photoresist masters. We show that the PU nanopillars and nanoholes increase the neurite length of pheochromocytoma 12 (PC12) cells through unique growth cone interactions. Moreover, we demonstrate, for the first time, that hierarchically patterned nano-/microstructured PU films enhance both PC12 neurite elongation and alignment, showing the potential use of our proposed method for the micro-/nanopatterning of polymers for nerve tissue engineering.

Preparation and properties of lignin-based polyurethane materials

In this paper, lignin-based polyurethane (LPU) films were successfully prepared by tape casting using modified alkaline lignin instead of partial polycarbonate diol (PCDL) in reaction with isophorone diisocyanate (IPDI), with diethylene glycol (DEG) as chain extender and dibutyltin dilaurate (DBTDL) as catalyst. The factors influencing the hydroxylation modification of alkali lignin were discussed, and the optimal reaction conditions were determined: reaction temperature of 50 °C, reaction time of 60 min, hydrogen peroxide to lignin mass ratio of 1.2:1, and iron hydroxide to alkali lignin mass ratio of 2 %. The lignin-based polyurethane films with different R values were also prepared by changing the ratio of isocyanate groups to hydroxyl groups (R-value), and the effects of different R values on the polyurethane properties were investigated. It was characterized by Fourier transform infrared spectroscopy (FTIR), mechanical property tests, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), moisture and oxygen permeability property tests, and UV spectroscopy tests. The results show that changing the R-value can improve the mechanical properties, thermal stability, barrier properties, and UV shielding properties of polyurethane materials. When the R-value is 1.8, the lignin-based polyurethane film material has the best performance.

Carbon nanotube/castor oil‐based waterborne polyurethane films with gradient structure for absorption‐dominated electromagnetic interference shielding and Joule heating

AbstractConductive polymer composites are highly demanded for practical application in electromagnetic interference shielding and Joule heating owing to their excellent flexibility and adjustable conductivity. Herein, a thin film with a gradient structure, comprising carbon nanotube/castor oil‐based waterborne polyurethane (CNT/WPU), has been fabricated through solution mixing utilizing casting technology. Scanning electron microscopy images confirm that CNTs are enriched at the top of the obtained CNT/WPU film, leading to a low resistance value. Consequently, the resultant gradient CNT/WPU films exhibit shielding effectiveness, specific shielding effectiveness, and an absorption coefficient of 22.8 dB, 1091 dB/cm, and 0.697, respectively, indicating a predominance of absorption in the shielding capacity. The temperature at the surface of the resultant gradient CNT/WPU film reaches ~77°C at a voltage of 20 V. The film with a CNT content of 14.1 wt% exhibits a good stress of 11.7 MPa and a high module of 39.9 MPa. Therefore, the obtained CNT/WPU films can be applied as thin shielding materials or coating.Highlights Fabricating a gradient CNT/castor oil–based waterborne polyurethane films. Exhibiting shielding effectiveness of 22.8 dB and A‐value of 0.697. Steady‐state temperature of CNT/WPU reaches 77°C at 20 V. Possessing green EMI shielding capability.

Development of Thermoplastic Polyurethane Films for the Replacement of Corneal Endothelial Function of Transparency Maintenance.

Endothelial keratoplasty is the main surgical procedure for treating corneal endothelial dysfunction (CED), which is limited by the global shortage of donor corneas. Herein, we developed and evaluated the modified thermoplastic polyurethane (M-TPU) films with gelatin-glycidyl methacrylate to replace the corneal endothelial function and maintain corneal transparency. The films displayed comparable light transmission characteristics with normal corneas and clinically favorable mechanical properties for surgical manipulation. After surface modification, the hydrophilicity and biocompatibility of M-TPU films were significantly improved. In the rabbit CED model, the M-TPU implants exhibited firm adhesion to the exposed stromal surface. The rabbit corneal transparency and thickness could be restored completely within 1 week of M-TPU film implantation. There was no significant inflammatory reaction and immune rejection during the follow-up of 1 month. Proteomic analysis suggested that the complement inhibition, the increase of mineral absorption, and the decrease of P53 apoptosis signaling pathway and lysine degradation might be beneficial in maintaining the corneal transparency. Overall, our study demonstrated the potential of M-TPU films as artificial implants for the replacement of corneal endothelial function to restore corneal thickness and transparency.

Sand Erosion Resistance and Failure Mechanism of Polyurethane Film on Helicopter Rotor Blades.

Polyurethane is widely used on the surface of composite materials for rotor blades as sand erosion protection materials. The failure mechanism investigation of polyurethane film under service conditions is useful for developing the optimal polyurethane film for rotor blades. In this article, the sand erosion test parameters were ascertained according to the service environment of the polyurethane film. The sand erosion resistance and failure mechanism of polyurethane film at different impact angles were analyzed by an infrared thermometer, a Fourier transform infrared spectrometer (FTIR), a differential scanning calorimeter (DSC), a field emission scanning electron microscope (FESEM), and a laser confocal microscope (CLSM). The results show that the direct measurement method of volume loss can better characterize the sand erosion resistance of the polyurethane film compared to traditional mass loss methods, which avoids the influence of sand particles embedded in the polyurethane film. The sand erosion resistance of polyurethane film at low-angle impact is much lower than that at high-angle impact. At an impact rate of 220 m/s, the volume loss after sand erosion for 15 min at the impact angle of 30° is 57.8 mm3, while that at the impact angle of 90° is only 2.6 mm3. The volume loss prediction equation was established according to the experimental data. During low-angle erosion, the polyurethane film damage is mainly caused by sand cutting, which leads to wrinkling and accumulation of surface materials, a rapid increase in roughness, and the generation of long cracks. The linking of developing cracks would lead to large-scale shedding of polyurethane film. During high-angle erosion, the polyurethane film damage is mainly caused by impact. The connection of small cracks caused by impact leads to the shedding of small pieces of polyurethane, while the change in the roughness of the film is not as significant as that during low-angle erosion. The disordered arrangement of the soft and hard blocks becomes locally ordered under the action of impact and cutting loads. Then, the disordered state is restored after the erosion test finishes. The erosion of sand particles leads to an increase in the temperature of the erosion zone of the polyurethane film, and the maximum temperature rise is 6 °C, which does not result in a significant change in the molecular structure of the polyurethane film. The erosion failure mechanism is cracking caused by sand cutting and impact.

CDs microcapsules polyurethane film with improved light environment, self-healing and high strength for plant greenhouses to promote plant growth

Carbon dots (CDs) have photoconversion performance and have a wide range of applications in agriculture. However, the solution of CDs is susceptible to quench under evaporation of sunlight and is easy to run-off when influenced by the external environment. Here, PVA-coated CDs were used to overcome the solid-state quenching and to prepare CDs microcapsules-polyurethane Film for plant cultivation. In this work, CDs microcapsules which can convert ultraviolet light into blue light for plant growth, were prepared by the “water/oil/water” method, and light-converting CDs microcapsules polyurethane film (CMPF) was prepared by doping CDs microcapsules with polyurethane. The study showed that polyurethane film has good mechanical properties and self-healing ability, the CMPF was able to effectively promote the growth of lettuce, and the effect was most significant at the CDs microcapsules concentration of 4000 mg/L. Compared with the blank group, the fresh and dry weights were increased by 177 % and 143.5 %, respectively, and the content of chlorophyll a, chlorophyll b, carotenoids, and soluble protein were increased by 14.5 %, 188.5 %, 43.3 %, and 17.9 %, respectively. Application of CDs to modulate plant lighting growth regulators for efficient use of ultraviolet (UV) light.

Fluorescent naphthalimide containing polyurethanes for the detection and removal of Hg2+/Hg+ and Fe3+ ions

AbstractHeavy metal (HM) pollution is getting worse with the society progress. Identification and separation of HM ions are urgent issues in environmental protection and social development. In this work, 4‐bromo‐1,8‐naphthalic anhydride was first reacted with amino‐propylene glycol to synthesize naphthimide fluorophores bearing two hydroxyl groups. And then, –Br was substituents by 8‐mercaptoquinoline, 2‐mercaptoimidazole, and 4‐mercaptopyridine, respectively. Eventually, it was reacted with 1,5‐naphthalene diisocyanate (NDI) to synthesize fluorescent polyurethane (PU) films through the reaction between –OH and –NCO. It is found that the PU film not only has a specific identification ability to Hg2+/Hg+ and Fe3+ ions, but also can efficiently remove Hg2+/Hg+ and Fe3+ ions through adsorption. In addition, selective identification by fluorescence quenching was investigated. It is due to the photoinduced electron transfer mechanism (PET). Furthermore, the lowest detection limits for Fe3+, Hg2+, and Hg+ were 6.0 × 10−7 M, 4.7 × 10−7 M, and 9.7 × 10−7 M, respectively, which reflected the sensitivity of the probe and made it fluorescence probes. The three fluorescent small molecules were incorporated into PU, which not only retain their identification function, but also serve the purpose of adsorption and separation of HM ions.

High‐efficiency self‐repairing polyurethane based on synergy of disulfide bonds and graded hydrogen bonds

AbstractDesigning an elastomer that possesses both mechanical strength and self‐healing properties is a challenging. In this study, a polyurethane elastomer (PUSTP) was successfully synthesized, featuring disulfide bonds along the main chain and graded intermolecular hydrogen bonds. The results demonstrated that the mechanical properties of the polyurethane elastomer improved with an increase in the number of disulfide bonds increased. Specifically, when the molar ratio of disulfide bonds to IPDA was 5:5, the tensile strength of the composite elastomeric film was 5.22 MPa, with an elongation of 1820.26%. Furthermore, the material exhibited robust thermal stability after undergoing repair at 70°C for 12 h, the mechanical strength of the polyurethane membrane remained unchanged, showing outstanding self‐healing capabilities. Additionally, the polyurethane film served as the substrate material for crafting self‐healing conductive devices, which maintained excellent electrical conductivity even after damage repair. This flexible material, combining impressive mechanical recovery capabilities with electrical performance, holds significant promise for a wide array of applications.

Rational Design, Synthesis, and Structure-Property Relationship Studies of a Library of Thermoplastic Polyurethane Films as an Effective and Scalable Encapsulation Material for Perovskite Solar Cells.

Hybrid organic-inorganic metal halide perovskite solar cell (PSC) technology is experiencing rapid growth due to its simple solution chemistry, high power conversion efficiency (PCE), and potential for low-cost mass production. Nevertheless, the primary obstacle preventing the upscaling and widespread outdoor deployment of PSC technology is the poor long-term device stability, which stems from the inherent instability of perovskite materials in the presence of oxygen and moisture. To address this issue, in this work, we have synthesized a series of thermoplastic polyurethanes (TPUs) through a rational design by utilizing polyols having different molecular weights and diverse isocyanates (aromatic and aliphatic). Thorough characterization of these TPUs (ASTM and ISO standards) along with structure-property relationship studies were carried out for the first time and were then used as the encapsulation material for PSCs. The prepared TPUs were robust and adhered well with the glass substrate, and the use of low temperature during the encapsulation process avoided the degradation of the perovskite absorber and other organic layers in the device stack. The encapsulated devices retained more than 93% of their initial power conversion efficiency (PCE) for over 1000 h after exposure to harsh environmental conditions such as high relative humidity (80 ± 5% RH). Furthermore, the encapsulated perovskite absorbers showed remarkable stability when they were soaked in water. This article demonstrates the potential of TPU as a suitable and easily scalable encapsulant for PSCs and pave the way for extending the lifetime and commercialization of PSCs.