Material Science and Engineering Program

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  • Article

    Biobased Interpenetrating Polymer Network Membranes for Sustainable Molecular Sieving

    (American Chemical Society (ACS), 2024-02-20) Cavalcante, Joyce; Oldal, Diana Gulyas; Peskov, Maxim; Beke, Aron K.; Hardian, Rifan; Schwingenschlögl, Udo; Szekely, Gyorgy; Chemical Engineering Program; Physical Science and Engineering (PSE) Division; Advanced Membranes and Porous Materials Research Center; Material Science and Engineering Program; Applied Physics; KAUST Solar Center (KSC)

    There is an urgent need for sustainable alternatives to fossil-based polymer materials. Through nanodomain engineering, we developed, without using toxic cross-linking agents, interpenetrating biopolymer network membranes from natural compounds that have opposing polarity in water. Agarose and natural rubber latex were consecutively self-assembled and self-cross-linked to form patchlike nanodomains. Both nano-Fourier transform infrared (nano-FTIR) spectroscopy and computational methods revealed the biopolymers’ molecular-level entanglement. The membranes exhibited excellent solvent resistance and offered tunable molecular sieving. We demonstrated control over separation performance in the range of 227–623 g mol–1 via two methodologies: adjusting the molecular composition of the membranes and activating them in water. A carcinogenic impurity at a concentration of 5 ppm, which corresponds to the threshold of toxicological concern, was successfully purged at a negligible 0.56% pharmaceutical loss. The biodegradable nature of the membranes enables an environmentally friendly end-of-life phase; therefore, the membranes have a sustainable lifecycle from cradle to grave.

  • Article

    Cutting off the upstream and downstream costs for CO2 electroreduction by upcycling fermentation emissions into ethanol

    (Royal Society of Chemistry (RSC), 2024) Sun, Ruofan; Zhao, Jiwu; Lu, Xu; Material Science and Engineering Program; Physical Science and Engineering (PSE) Division; Mechanical Engineering Program; Clean Combustion Research Center; KAUST Solar Center (KSC)

    Electrochemical reduction of CO2 (CO2RR), when powered by renewables, opens up a new avenue to mitigate the greenhouse gas while producing value sustainably. Nevertheless, this technology has been largely limited by the high costs of the upstream CO2 feed and downstream product separation. Here we report a hybrid bio-electrochemical system, integrating yeast fermentation with CO2RR in one single cell, that upcycles the fermentation-emitted CO2 into ethanol. We engineer a CuO-Ag tandem electrocatalyst with rationally designed CuO-Ag interfaces that pose minimal impact on the yeast, while efficiently converting CO2 into ethanol against side reactions, such as hydrogen evolution and glucose reduction. We showcase the win-win model enabled by this hybrid system—the CO2RR cost can be cut by 17.8% because the fermentation process provides a free, high-purity CO2 source and free ethanol distillation and in return, the CO2RR reduces the CO2 emissions of fermentation and increases the final ethanol product concentration. This proof-of-concept procedure sheds light on a tempting possibility for a cost-effective CO2 value chain.

  • Conference Paper

    Interfacial Charge Carrier Recombination Processes in Metal Halide Perovskite Solar Cells

    (FUNDACIO DE LA COMUNITAT VALENCIANA SCITO, 2023-12-18) Laquai, Frédéric; Material Science and Engineering Program; KAUST Solar Center (KSC); Applied Physics; Physical Science and Engineering (PSE) Division

    Interfacial charge carrier recombination is currently one of the major performance bottlenecks in single- and multi-junction metal halide perovskite (MHP) solar cells. In our work, we investigate interfacial charge carrier recombination processes in state-of-the-art MHP thin films and device structures by transient spectroscopies including transient reflection, transient absorption, time-resolved photoluminescence, and time-domain terahertz spectroscopy across a wide dynamic range from femto- to microseconds. The MHPs investigated are multi-cation (mixed) halide perovskites as neat MHP thin films, passivated MHP thin films, perovskite films adjacent to charge transport layers (CTLs), MHP films adjacent to CTLs with additional interlayers (ITLs) and in the presence of electrodes, as well as MHP films on transparent conductive oxides (TCOs) with and without common self-assembled monolayers (SAMs). Organic CTLs are also used, since they allow direct probing of the carrier dynamics in the CTL (not only in the perovskite film), thereby allowing to distinguish between carrier extraction and interfacial recombination. Our spectroscopic experiments are supported by computational studies providing insight into the role of (bulk and surface/interface) defects on carrier recombination, the chemistry of defect passivation at interfaces, and interfacial carrier extraction and recombination dynamics. Our studies provide in-depth insight into interfacial charge carrier recombination processes at various types of interfaces in perovskite devices and reveal pathways to mitigate those losses to enhance the device Voc and quantum efficiency in both single- and multijunction photovoltaic solar cells.

  • Conference Paper

    The impact of ion migration on the performance and stability of perovskite-based tandem solar cells

    (FUNDACIO DE LA COMUNITAT VALENCIANA SCITO, 2023-12-18) Stolterfoht, Martin; Shah, Sahil; Köhnen, Eike; Ugur, Esma; Thiesbrummel, Jarla; Khenkin, Mark; Holte, Lucas; Scherler, Florian; Forozi, Paria; Yang, Fengjui; Peña-Camargo, Francisco; Aydin, Erkan; Lang, Felix; Neher, Dieter; Snaith, Henry; De Wolf, Stefaan; Albrecht, Steve; Diekmann, Jonas; Material Science and Engineering, KAUST Solar Centre, Physical science and engineering division, King Abdullah University of Science and Technology, 4700 KAUST, Thuwal 23955-6900, Kingdom of Saudi Arabia; Material Science and Engineering Program; KAUST Solar Center (KSC); Physical Science and Engineering (PSE) Division; The Chinese University of Hong Kong, Electronic Engineering Department, Shatin N.T., Hong Kong SAR; Physik weicher Materie, Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24–25, 14776 Potsdam, Germany; Helmholtz-Zentrum Berlin für Materialien und Energie, Solar Energy Division, 12489 Berlin, Germany; Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom; National Renewable Energy Laboratory, NREL, Golden, CO, USA.

    Mobile ions play a significant role in perovskite photovoltaics (PV), yet their impact on the overall performance and stability of tandem solar cells (TSCs) remains largely unexplored. Moreover, the effects of hysteresis in the current-voltage (JV) characteristic and ionic field screening are usually not considered to be a major problem anymore in high-performance tandem cells due to the introduction of comparatively stable and well-performing pin-type perovskite cells. This conclusion is based on the established practice of using a relatively slow JV scanning rate for the characterization of these devices. Here, based on recent work,[1-4] I will present a comprehensive study that combines an experimental analysis of ionic losses in Si/perovskite and all-perovskite TSCs during device aging with drift-diffusion simulations. Our findings demonstrate that mobile ions have a significant influence on the hysteresis of both tandem cells at high JV scan speeds (e.g. 400 V/s) as well as on performance degradation due to field screening. Additionally, subcell-dominated “fast-hysteresis” measurements on all-perovskite tandems reveal more pronounced ionic losses in the wide-bandgap subcell during aging, which we attribute to its tendency for halide segregation. Drift-diffusion simulations fully corroborate the results. Finally, I will discuss how we can use the obtained ionic properties as an early fingerprint to predict the long-term stability of perovskite cells. Overall, our research provides valuable insights into how ion migration influences the energy-lifetime yield of perovskite PV and highlights new strategies to improve the stability of all perovskite-based single- and multi-junction cells.

  • Conference Paper

    Solution-based MXene Contacts for Electronic Devices

    (FUNDACIO DE LA COMUNITAT VALENCIANA SCITO, 2023-12-18) Alshareef, Husam N.; Material Science and Engineering Program; Physical Science and Engineering (PSE) Division

    MXenes have recently shown promising properties in a variety of device applications. In this talk, I will present recent results on using MXenes as gate materials in thin film transistors using MoS2 and GaN semiconductor channels. Gate controllability is a key factor that determines the performance of GaN high electron mobility transistors (HEMTs). However, at the traditional metal-GaN interface, the direct chemical interaction between metal and GaN can result in fixed charges and traps, which can significantly deteriorate the gate controllability. We show that Ti3C2Tx MXene films integrated into GaN HEMTs as the gate contact induce van der Waals heterojunctions between MXene films and GaN without direct chemical bonding. The GaN HEMTs with enhanced gate controllability exhibited an extremely low off-state current (IOFF) of 10−7 mA/mm, a record high ION/IOFF current ratio of ~1013 (which is six orders of magnitude higher than conventional Ni/Au contact), a high off-state drain breakdown voltage of 1085 V, and a near-ideal subthreshold swing of 61 mV/dec. However, MXenes do not fare as well when used as contacts in MoS2 transistors. The origin in this difference will be discussed in the context of the interface between MXene and GaN and MoS2 channel materials.