Photo-doping of spiro-OMeTAD for highly stable and efficient perovskite solar cells

Advanced Materials

High‐performance perovskite solar cells (PSCs) typically require interfacial passivation, yet this is challenging for the buried interface, owing to the dissolution of passivation agents during the deposition of perovskites. Here, this limitation is overcome with in situ buried‐interface passivation—achieved via directly adding a cyanoacrylic‐acid‐based molecular additive, namely BT‐T, into the perovskite precursor solution. Classical and ab initio molecular dynamics simulations reveal that BT‐T spontaneously may self‐assemble at the buried interface during the formation of the perovskite layer on a nickel oxide hole‐transporting layer. The preferential buried‐interface passivation results in facilitated hole transfer and suppressed charge recombination. In addition, residual BT‐T molecules in the perovskite layer enhance its stability and homogeneity. A power‐conversion efficiency (PCE) of 23.48% for 1.0 cm2 inverted …

Science

High-purity precursor materials are vital for high-efficiency perovskite solar cells (PSCs) to reduce defect density caused by impurities in perovskite. In this study, we present aqueous synthesized perovskite microcrystals as precursor materials for PSCs. Our approach enables kilogram-scale mass production and synthesizes formamidinium lead iodide (FAPbI3) microcrystals with up to 99.996% purity, with an average value of 99.994 ± 0.0015%, from inexpensive, low-purity raw materials. The reduction in calcium ions, which made up the largest impurity in the aqueous solution, led to the greatest reduction in carrier trap states, and its deliberate introduction was shown to decrease device performance. With these purified precursors, we achieved a power conversion efficiency (PCE) of 25.6% (25.3% certified) in inverted PSCs and retained 94% of the initial PCE after 1000 hours of continuous simulated solar …

Nature

Solar fuels offer a promising approach to provide sustainable fuels by harnessing sunlight,. Following a decade of advancement, Cu2O photocathodes are capable of delivering a performance comparable to that of photoelectrodes with established photovoltaic materials, –. However, considerable bulk charge carrier recombination that is poorly understood still limits further advances in performance. Here we demonstrate performance of Cu2O photocathodes beyond the state-of-the-art by exploiting a new conceptual understanding of carrier recombination and transport in single-crystal Cu2O thin films. Using ambient liquid-phase epitaxy, we present a new method to grow single-crystal Cu2O samples with three crystal orientations. Broadband femtosecond transient reflection spectroscopy measurements were used to quantify anisotropic optoelectronic properties, through which the carrier mobility along the [111 …

The journal of physical chemistry letters

The synthesis and control of properties of p-type ZnO is crucial for a variety of optoelectronic and spintronic applications; however, it remains challenging due to the control of intrinsic midgap (defect) states. In this study, we demonstrate a synthetic route to yield colloidal ZnO quantum dots (QD) via an enhanced sol–gel process that effectively eliminates the residual intermediate reaction molecules, which would otherwise weaken the excitonic emission. This process supports the creation of ZnO with p-type properties or compensation of inherited n-type defects, primarily due to zinc vacancies under oxygen-rich conditions. The in-depth analysis of carrier recombination in the midgap across several time scales reveals microsecond carrier lifetimes at room temperature which are expected to occur via zinc vacancy defects, supporting the promoted p-type character of the synthesized ZnO QDs.

Advanced Functional Materials

Perovskite solar cells have led the new surge of solar energy research. However, their instability is a pressing issue mostly attributed to the perovskite interface with charge‐selective transport layers. In this work, diethylammonium iodide (DEAI) surface treatment is used to mitigate interfacial non‐radiative recombination losses by forming a mixed phase of layered perovskite on the surface. This results in enhanced device performance with the power conversion efficiency of 23.3% and improved operational stability under thermal stress. Moreover, the DEAI treatment facilitates interfacial hole transfer, enabling a carbon‐based hole transport layer‐free perovskite solar cell with a power conversion efficiency of 15.6%.

Advanced Materials

Efficient and robust n‐i‐p perovskite solar cells necessitate superior organic hole‐transport materials with both mechanical and electronic prowess. Deciphering the structure−property relationship of these materials is crucial for practical perovskite solar cell applications. Through direct arylation, we synthesized two high glass transition temperature molecular semiconductors, DBC‐ETPA (202 °C) and TPE‐ETPA (180 °C), using dibenzo[g,p]chrysene (DBC) and 1,1,2,2‐tetraphenylethene (TPE) tetrabromides with triphenylene–ethylenedioxythiophene‐dimethoxytriphenylamine (ETPA). In comparison to spiro‐OMeTAD, both semiconductors exhibit shallower HOMO energy levels, resulting in increased hole densities (generated by air oxidation doping) and accelerated hole extraction from photoexcited perovskite. Experimental and theoretical studies highlight the more rigid DBC core, enhancing hole mobility due to …

Nano Letters

Halide perovskite-based resistive switching memory (memristor) has potential in an artificial synapse. However, an abrupt switch behavior observed for a formamidinium lead triiodide (FAPbI3)-based memristor is undesirable for an artificial synapse. Here, we report on the δ-FAPbI3/atomic-layer-deposited (ALD)-SnO2 bilayer memristor for gradual analogue resistive switching. In comparison to a single-layer δ-FAPbI3 memristor, the heterojunction δ-FAPbI3/ALD-SnO2 bilayer effectively reduces the current level in the high-resistance state. The analog resistive switching characteristics of δ-FAPbI3/ALD-SnO2 demonstrate exceptional linearity and potentiation/depression performance, resembling an artificial synapse for neuromorphic computing. The nonlinearity of long-term potentiation and long-term depression is notably decreased from 12.26 to 0.60 and from −8.79 to −3.47, respectively. Moreover, the δ-FAPbI3 …

Scientific Reports

In this work we study in-depth the antireflection and filtering properties of ultrathin-metal-film-based transparent electrodes (MTEs) integrated in thin-film solar cells. Based on numerical optimization of the MTE design and the experimental characterization of thin-film perovskite solar cell (PSC) samples, we show that reflection in the visible spectrum can be strongly suppressed, in contrast to common belief (due to the compact metal layer). The optical loss of the optimized electrode (~ 2.9%), composed of a low-resistivity metal and an insulator, is significantly lower than that of a conventional transparent conductive oxide (TCO ~ 6.3%), thanks to the very high transmission of visible light within the cell (> 91%) and low thickness (< 70 nm), whereas the reflection of infrared light (~ 70%) improves by > 370%. To assess the application potentials, integrated current density > 25 mA/cm2, power conversion …

Solar RRL

Narrow‐bandgap Sn–Pb‐alloyed perovskite is potential for a bottom cell in perovskite tandem solar cells. However, Sn‐contained perovskites tend to be readily oxidized in air atmosphere, which has ill influence on stability and photovoltaic performance. Herein, a method to suppress oxidation of divalent tin via post‐treatment of perovskite film with phenylhydrazine is reported. Phenylhydrazine‐treated FA0.5MA0.5Pb0.5Sn0.5I3 perovskite films effectively reduce the hole traps caused by the oxidation of Sn2+ on the perovskite surfaces. In addition, surface energetics are well aligned by post‐treatment, which is beneficial for voltage gain and charge transport. As a result, power conversion efficiency (PCE) is increased from 18.16% to 20.67% after post‐treatment due mainly to the significant improvement of open‐circuit voltage from 0.75 to 0.83 V. Furthermore, the device stability is improved, where 91.67% of initial …

Advanced Materials Interfaces

Interfacial space charges significantly influence transport and recombination of charge carriers in optoelectronic devices. Due to the mixed ionic‐electronic conducting properties of halide perovskites, not only electronic effects, but also ionic interactions at their interfaces need to be considered in the analysis of space charges. Understanding of these interactions and their control is currently missing. This study elucidates the ionic effects on space charge formation at the interface between methylammonium lead iodide (MAPI) and alumina, and its modulation through surface modification using organic molecules. Embedding insulating alumina nanoparticles within MAPI films leads to enhancement of the electronic conductivity. This effect is consistent with the formation of an interfacial inversion layer in MAPI and can only be explained on the basis of ionic interactions. Such an effect is attenuated by surface …

Solar fuels offer a promising approach to provide sustainable fuels by harnessing sunlight. Following a decade of advancement, Cu2O photocathodes are capable of delivering a performance comparable to that of photoelectrodes with established photovoltaic materials. However, considerable bulk charge carrier recombination that is poorly understood still limits further advances in performance. Here we demonstrate performance of Cu2O photocathodes beyond the state-of-the-art by exploiting a new conceptual understanding of carrier recombination and transport in single-crystal Cu2O thin films. Using ambient liquid-phase epitaxy, we present a new method to grow single-crystal Cu2O samples with three crystal orientations. Broadband femtosecond transient reflection spectroscopy measurements were used to quantify anisotropic optoelectronic properties, through which the carrier mobility along the [111] orientation was found to be an order of magnitude higher than those along other orientations. Driven by these findings, we developed a polycrystalline Cu2O photocathode with an extraordinarily pure (111) orientation and (111) terminating facets using a simple and low-cost method, which delivers 7 mA cm− 2 current density (more than 70% improvement compared to that of state-of-the-art electrodeposited devices) at 0.5 V versus a reversible hydrogen electrode under air mass 1.5 G illumination, and stable operation over at least 120 h.

Joule

Perovskite solar cells (PSCs) have demonstrated a comparable efficiency to Si-based cells. However, the buried interface with weak adhesion remains a critical issue since the ion migration enhanced by the built-in electric field at this interface might lead to instability. We report here that adjusting the energy-level alignment at the weak adhesion homojunction interface can mitigate ion migration and thereby enhance the stability and photovoltaic performance of PSCs. Functional molecules with self-assembled monolayer characteristics were introduced to the surface of the SnO2 layer using silane derivatives, which tuned the work function of the homojunction depending on the functional groups in the molecules and thereby significantly reduced the built-in electric field. The PSC exhibited a power conversion efficiency (PCE) of 25.3%. The maximum power point (MPP) tracking under continuous illumination …

Energy & Environmental Science

Light-induced degradation in metal halide perovskites is a major concern that can potentially hamper the commercialization of perovskite optoelectronic devices. The phenomena viz. ion migration, phase segregation, and defect intolerance are believed to be the factors behind the degradation. However, a detailed mechanistic understanding of how and why light reduces the long-term stability of perovskites is still lacking. Here, by combining multiscale characterization techniques and computational studies, we uncover the role of white light in the surface degradation of state-of-the-art FAPbI3-rich perovskite absorbers (reaching up to 22% PCE in solar cells). We unravel the degradation kinetics and found that white light triggers the chemical degradation of perovskite into secondary phases with higher work function and metallic I–V characteristics. Furthermore, we demonstrate that perovskite degradation is triggered …

Energy & Environmental Materials

The systematic advances in the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs) have been driven by the developments of perovskite materials, electron transport layer (ETL) materials, and interfacial passivation between the relevant layers. While zinc oxide (ZnO) is a promising ETL in thin film photovoltaics, it is still highly desirable to develop novel synthetic methods that allow both fine‐tuning the versatility of ZnO nanomaterials and improving the ZnO/perovskite interface. Among various inorganic and organic additives, zwitterions have been effectively utilized to passivate the perovskite films. In this vein, we develop novel, well‐characterized betaine‐coated ZnO QDs and use them as an ETL in the planar n‐i‐p PSC architecture, combining the ZnO QDs‐based ETL with the ZnO/perovskite interface passivation by a series of ammonium halides (NH4X, where X = F, Cl, Br). The …

Advanced Materials Interfaces

Hygroscopic and acidic nature of organic hole transport layers (HTLs) insisted to replace it with metal oxide semiconductors due to their favorable charge carrier transport with long chemical stability. Apart from large direct bandgap and high optical transmittance, ionization energy in the range of −5.0 to −5.4 eV leads to use NiO as HTL due to good energetic matching with lead halide perovskites. Analyzing X‐ray photoelectron spectroscopic (XPS) data of NiO, it is speculated that p‐type conductivity is related to the NiOOH or Ni2O3 states in the structure and the electrical conductivity can be modified by altering the concentration of nickel or oxygen vacancies. However, it is difficult to separate the contribution from nonlocal screening, surface effect and the presence of vacancy induced Ni3+ ion due to very strong satellite structure in the Ni 2p XPS spectrum of NiO. Thus, an effective approach to analyze the NiO XPS …

ACS Energy Letters

Although perovskite solar cells (PSCs) have demonstrated power conversion efficiency (PCE) as high as 26%, instability caused by the heterointerfaces has been an issue. Since the thermal expansion coefficient of perovskite is higher than that of SnO2, in-plane tensile strain formed at the perovskite/SnO2 interface is one of the causes of the instability of PSCs. We report here an effective methodology to regulate the strain via surface modification of the SnO2 layer with a bifunctional molecule of phosphorylethanolamine (PEA) bearing phosphate and amine groups linked by an alkyl chain. The grazing incidence X-ray diffraction data showed that an in-plane tensile strain observed upon deposition of the perovskite film on the bare SnO2 layer was substantially released by modifying the SnO2 surface with PEA. The strain-less interface resulted in an increase in PCE from 22.87% to 24.35%. Moreover, the …

Joule

Perovskite-silicon tandem solar cells have now surpassed the 30% efficiency mark, which has led to the acceleration of industrialization efforts. With most research focusing on 2-terminal tandems, we focus our investigation on 3-terminal tandem solar cells, a configuration that promises a higher energy yield under realistic operating conditions. We specifically focus on the simulation of the performance of finite strings of 3-terminal tandem cells interconnected in various voltage-matching configurations. To experimentally validate our string model, we produced, characterized, and modeled a string of twelve 3-terminal perovskite-silicon tandems interconnected in different configurations. The individual tandems of the string have an active area of about 25 cm2 and an efficiency from 24.3% to 27.3% when measured in a 2-terminal configuration. Our findings reveal that 3-terminal tandem strings can outperform their 2 …

Joule

This study assesses the system-level impacts of carbon-free electricity procurements by voluntary actors in the western United States, accounting for induced changes in both system operations and installed capacities. We find that in the current US policy environment, procurement strategies that match participants' demand with carbon-free generation on an annual basis have minimal impact on long-run system-level CO2 emissions. Similar outcomes occur when participants calculate their annual emission impacts using short-run marginal emission rates and attempt to offset these with their procurements. In contrast, we find that matching participants' demand on an hourly basis with carbon-free generation can drive significant reductions in system-level CO2 emissions while incentivizing advanced clean firm generation and long-duration storage technologies that would not otherwise see market uptake. Greater …

Joule

Excellent thermoelectric materials can be obtained by various synthesis procedures and optimization strategies, and the elaborately designed composition and microstructure benefit thermoelectric parameter decoupling. Herein, a high-performance mixed natural mineral (CQB), composed by chalcocite, quartz, and bismuthinite, enables direct thermoelectric energy conversion. The network of quartz layers is embedded into the matrix and blocks Cu ion long-range migration by producing the natural rheostat and voltage division circuit. The thermoelectric performance, mechanical strength, and electrical stability of natural minerals are found to be highly superior to the artificially synthesized Cu2S material. Learning from nature, a strategy for blocking mobile Cu+ ions in Cu-based superionic conductors is proposed. Various Cu-based superionic conductors, composited with insulating macroscale glass sheets, have …

Joule

Perovskite/perovskite/silicon triple-junction solar cells hold promise for surpassing their two-junction counterparts in performance. Achieving this requires monolithic integration of a ∼2.0 eV band-gap perovskite subcell, characterized by a high bromide:iodide ratio (>7:3), and with low-temperature processability and high optoelectronic quality. However, light-induced phase segregation in such perovskites remains a challenge. To address this, we propose modifying the wide-band-gap perovskite with potassium thiocyanate (KSCN) and methylammonium iodide (MAI) co-additives, where SCN− increases the perovskite grain size, reducing the grain boundary defect density; K+ immobilizes the halide, preventing the formation of halide vacancies; and MA+ eliminates the residual light-destabilizing SCN− in the perovskite films via double displacement reactions. Our co-additive strategy enables enhanced photostability …

Joule

Perovskite-silicon tandem solar cells have now surpassed the 30% efficiency mark, which has led to the acceleration of industrialization efforts. With most research focusing on 2-terminal tandems, we focus our investigation on 3-terminal tandem solar cells, a configuration that promises a higher energy yield under realistic operating conditions. We specifically focus on the simulation of the performance of finite strings of 3-terminal tandem cells interconnected in various voltage-matching configurations. To experimentally validate our string model, we produced, characterized, and modeled a string of twelve 3-terminal perovskite-silicon tandems interconnected in different configurations. The individual tandems of the string have an active area of about 25 cm2 and an efficiency from 24.3% to 27.3% when measured in a 2-terminal configuration. Our findings reveal that 3-terminal tandem strings can outperform their 2 …

Joule

Despite the remarkable growth of perovskite photovoltaic technology, the performance and stability of flexible perovskite solar modules (f-PSMs) are still below the commercial level, and even the clear reasons for this have hardly been elucidated. Here, we found that flexible perovskite solar cells (f-PSCs) suffer from a trade-off between efficiency and stability due to the off-balance between surface coverage and the charge-transporting property when conventionally using colloidal SnO2 nanoparticles as an electron-transport layer (ETL). To resolve this trade-off, we newly designed an ETL that enhances the charge transport properties and mitigates the shunt sites, resulting in improved efficiency and operational stability. Therefore, we succeeded in achieving a certified efficiency of 21.8% in f-PSC (22.92% in-house) and 16.4% in f-PSM (900 cm2). Furthermore, we discovered that incomplete coverage gives rise to …

Joule

A widely used component of high-efficiency perovskite solar cells (PSCs) is the molecular hole-transport material (HTM) spiro-OMeTAD. This organic solid needs to be p-doped to acquire sufficient hole conductivity. However, the conventional doping method using LiTFSI in the air is slow, sensitive to the environment, and may lead to the deterioration of the PSCs by unintended oxidation or dopant migration. It is thus highly desirable to develop fast doping approaches that avoid exposing the PSC to ambient air and easy-to-move dopant ions. We report here that light absorption by spiro-OMeTAD itself triggers redox photochemistry that has so far been ignored. Strikingly, we found that Y(III) or La(III)-tBP complexes catalyze the symmetry-breaking charge separation of photo-excited spiro-OMeTAD, resulting in the efficient p-doping of the HTM. Using this photo-redox process, we realize PSCs with superior stability over …

Joule

Accurate prediction of battery lifetime is critical for ensuring timely maintenance and safety of batteries. Although data-driven methods have made significant progress, their model accuracy is often hampered by a scarcity of labeled data. To address this challenge, we developed a semi-supervised learning technique named partial Bayesian co-training (PBCT), enhancing the modeling of battery lifetime prediction. Leveraging the low-cost unlabeled data, our model extracts hidden information to improve the understanding of the underlying data patterns and achieve higher lifetime prediction accuracy. PBCT outperforms existing approaches by up to 21.9% on lifetime prediction accuracy, with negligible overhead for data acquisition. Moreover, our research suggests that incorporating unlabeled data into the training process can help to uncover critical factors that impact battery lifetime, which may be overlooked with a …

Joule

The recent successes of emerging photovoltaics (PVs) are largely driven by innovations in material science. However, closing the gap to commercialization still requires significant progress to match contradicting requirements, such as performance, longevity, and recyclability. In this perspective, we envision the layout of a digital twin for PV materials able to provide the necessary acceleration of innovation.The layout combines machine learning approaches, as performed in materials acceleration platforms (MAPs), with physical models and digital twin concepts used in engineering. This layout will allow the use of high-throughput (HT) experimentation in MAPs to improve the parametrization of quantum chemical and solid-state models. In turn, the improved and generalized models can be used to obtain the crucial structural parameters. HT experimentation will thus yield a detailed understanding of generally valid …

Joule

Three-dimensional (3D) polycrystalline perovskite is emerging as a promising candidate for high-brightness light-emitting applications. However, 3D perovskite light-emitting diodes (PeLEDs) are difficult to achieve high brightness, efficiency, and stability simultaneously, as they are limited by the trade-off between the advanced external quantum efficiency (EQE) and the inevitable roll-off. Here, we develop a 3D FAPbI3 perovskite material system that enables high brightness, efficiency, and long device lifetime simultaneously, engineered by an alkyl-chain-length-dependent ammonium salt molecule modulation strategy. We elucidate the roles of alkylammonium salts on crystal orientation management, grain size control, non-radiative recombination suppression, and thus device performances. Consequently, we simultaneously obtain efficient, ultra-bright, and stable PeLEDs with a high EQE of 23.2%, a record …

Joule

To achieve carbon neutrality, a significant increase in photovoltaic module production is needed, affecting material demand and recycling perspectives. Circular recycling is essential for managing the material flows of a multi-terawatt global photovoltaic fleet. Immediate action is required to prevent the accumulation of millions of tons of low-value waste. Circularity's importance is multi-faceted and varies across materials. Limited silver reserves and competition with other markets necessitate reducing or substituting silver. For polymers, constrained production capacities can also be mitigated through circular recycling. The photovoltaic industry's immense glass demand calls for circular recycling to avoid overwhelming alternative markets. Recycling silicon, aluminum, and copper is vital for the economic feasibility of recycling, especially if silver is replaced. Although prolonging module lifespan reduces yearly material …

Joule

Electrode materials that enable lithium (Li) batteries to be charged on timescales of minutes but maintain high energy conversion efficiencies and long-duration storage are of scientific and technological interest. They are fundamentally challenged by the sluggish interfacial ion transport at the anode, slow solid-state ion diffusion, and too fast electroreduction reaction kinetics. Here, we report that Li alloy anodes based on indium (In) exhibit fast Li surface and bulk diffusivities but moderate electroreduction reaction rates. The resultant LiIn anodes appear to belong to a unique class of inherently low second Damköhler (Da) number (LDA_II) materials, which are predicted to exhibit high Li reversibility at unconventionally high charge rates. We demonsterate this capability using Li-ion battery cells in which LiIn anodes are paired with a range of intercalation (e.g., LiFePO4 and LiNi0.8Co0.1Mn0.1O2), and conversion (e.g …

Joule

Alkali metals, as additives in perovskite solar cells (PSCs), have been extensively investigated for their impact on performance enhancement. This performance is sensitive to ion-driven interfacial recombination processes that lead to voltage losses and perform with negative capacitance features in impedance spectroscopy (IS). In this study, we exploited negative capacitance as a tool to systematically investigate the influence of Li, Na, and K on the photovoltage of the wide band-gap material MAPbBr3, known for historical photovoltage losses. Sodium cations were found to mitigate adverse interfacial recombination pathways, yielding a remarkable stabilized open-circuit potential of 1.65 V. Impedance measurements indicated sodium significant influence within the material's bulk, corroborated by time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy. These techniques confirmed the …

Joule

Luminescent solar concentrators (LSCs) are devices that concentrate light using a transparent matrix doped with chromophores. LSCs have the potential to outperform other concentration technologies due to their ability to concentrate diffuse light and reshape the solar spectrum to match the optimum spectral characteristics for photovoltaics. This study compares different LSC technologies, including solar windows, within a simulated real-world environment and outlines the impact of upcoming technologies to determine their commercialization potential. We utilized a year of real-world solar spectrum data from Boulder and Amsterdam and define the power efficiencies from different LSC configurations. We find that silicon PV generally outperforms even the best LSC over a calendar year. We outline the potential opportunities in the application of LSC systems relative to traditional photovoltaics.

Joule

Vibrant research has demonstrated that the layer-by-layer (LBL) approach can achieve a preferable vertical microstructure; however, the lack of precise control over vertical composition and molecular organization remains. Herein, we demonstrated a guest polymer-tailored LBL (GPT-LBL) strategy to achieve the p-i-n microstructure constructed by in situ monitoring pre-aggregation behaviors of non-fullerene acceptors. This superior structure with built-in interpenetrating networks alleviates the trap density states and the energy loss, improves hole transfer dynamics, and balances the charge transport, thus maximizing open-circuit voltage (VOC), short-circuit current density (JSC), and fill factor (FF) simultaneously. Consequently, a highly efficient GPT-LBL organic solar cell (OSC) with a power conversion efficiency (PCE) of 19.41% (certified 19.0%) was achieved. Noticeably, the large-area (1.03 cm2) device for GPT …

Joule

The authors are all devoted energy system and sustainability transformation scholars, who collaborate regularly and actively at global and local levels to advance the knowledge space of demand-side solutions and policies. They are members of a growing bottom-up initiative, the Energy Demand Changes Induced by Technological and Social Innovations (EDITS) network (https://iiasa.ac.at/projects/edits), which builds on various research disciplines to facilitate advances in modeling, data compilation, and analysis of the scope and breadth of the potential contributions of demand-side solutions for climate change mitigation, improved wellbeing for all, and sustainability, complementing supply-side solutions for decarbonizing the energy and material systems.

Joule

Energy demand flexibility from commercial buildings can play a critical role in the ongoing energy transition. There is an urgent need to redirect more research and deployment efforts toward real-world experimentation. Buildings-sector roadmaps overwhelmingly rely on simulations that imperfectly capture reality. We draw lessons from a review of two decades of literature on real-world flexibility and demand response experiments and from our "Living Laboratory" experiences at three major academic institutions in the United States. While the prevailing method is "model first, experiment second," there is also strong value in "experiment first, model second" and in improving our understanding of a system through experimentation while modeling it. Commercial building clusters on university and corporate campuses offer valuable and often untapped potential. They are both ideal test beds for research on energy …

Joule

n-type SnSe thermoelectrics has been seriously underdeveloped because of a lack of effective performance-enhancing strategies and doping/alloying agents. Herein, we report that conduction band electronic and phonon structures can be advantageously engineered simultaneously in both Pnma and Cmcm SnSe phases by dually incorporating Pb and Cd. They enhance the density of states near the conduction band edge in both phases by converging band minima and increasing effective mass (m0), consequently enhancing Seebeck coefficients (S) without damaging electrical conductivity. Because exclusively divalent Pb and Cd cations reduce innate Sn vacancies, carrier mobility decreases marginally despite the increased m0 and |S|. The tetrahedral Cd displaced from the cationic sublattice and much heavier Pb significantly soften and scatter phonon transport, depressing thermal conductivity significantly …

Joule

Excellent thermoelectric materials can be obtained by various synthesis procedures and optimization strategies, and the elaborately designed composition and microstructure benefit thermoelectric parameter decoupling. Herein, a high-performance mixed natural mineral (CQB), composed by chalcocite, quartz, and bismuthinite, enables direct thermoelectric energy conversion. The network of quartz layers is embedded into the matrix and blocks Cu ion long-range migration by producing the natural rheostat and voltage division circuit. The thermoelectric performance, mechanical strength, and electrical stability of natural minerals are found to be highly superior to the artificially synthesized Cu2S material. Learning from nature, a strategy for blocking mobile Cu+ ions in Cu-based superionic conductors is proposed. Various Cu-based superionic conductors, composited with insulating macroscale glass sheets, have …

Joule

Electrochemical CO2 reduction on Cu-based catalysts is a promising technique to convert CO2 to high-value C2 and C3 feedstocks. High carbon efficiency can be achieved in acidic electrolytes, but Cu-based catalysts show suppressed activity toward C2+ formation in acidic conditions. Acid removes the oxygen-containing species on Cu, which are necessary for C–C coupling. In this work, a gas diffusion electrode (GDE)/Cu/Ni-N-C tandem configuration, in which Ni-N-C served as a CO2-to-CO catalyst, expressed a 5-time enhancement of C2+ formation activity compared with GDE/Cu. Electrochemical measurements and finite element simulations indicate the improved C2+ formation activity was due to the elevated local pH rather than the increased CO concentration in the Cu catalyst layer. The major function of the CO-formation catalyst in the tandem system working in an acidic condition is to modulate the local …