arXiv subjects

Qingbo Meng

Publications and source records attributed to Qingbo Meng.

At least 19 recordsLinked to original sources

arXiv2024

High efficient sunlight-driven CO2 hydrogenation to methanol over NiZn intermetallic catalysts under atmospheric pressure

The synthesis of solar methanol through direct CO2 hydrogenation using solar energy is of great importance in advancing a sustainable energy economy. In this study, non-precious NiZn intermetallic/ZnO catalyst is reported to catalyze the hydrogenation of CO2 to methanol using sunlight irradiation (1sun). The NiZn-ZnO interface is identified as the active site to stabilize the key intermediates of HxCO*. At ambient pressure, the NiZn-ZnO catalyst demonstrates a methanol production rate of 127.5 umol g-1h-1 from solar driven CO2 hydrogenation, with a remarkable 100% selectivity towards methanol in the total organic products. Notably, this production rate stands as the highest record for photothermic CO2 hydrogenation to methanol in continuous-flow reactors with sunlight as the only requisite energy input. This discovery not only paves the way for the development of novel catalysts for CO2 hydrogenation to methanol but also marks a significant stride towards a full solar-driven chemical energy storage.

cond-mat.mtrl-sci↗

arXiv2024

Multi-interface engineering to realize all-solution processed highly efficient Kesterite solar cells

With the rapid development of Kesterite Cu2ZnSn(S, Se)4 solar cells in the past few years, how to achieve higher cost-performance ratio has become an important topic in the future development and industrialization of this technology. Herein, we demonstrate an all-solution route for the cell fabrication, in particular targeting at the solution processed window layer comprised of ZnO nanoparticles/Ag nanowires. A multi-interface engineering strategy assisted by organic polymers and molecules is explored to synergistically improve the film deposition, passivate the surface defects and facilitate the charge transfer. These efforts help us achieve high-performance and robust Kesterite solar cells at extremely low time and energy costs, with efficiency records of 14.37% and 13.12% being realized in rigid and flexible Kesterite solar cells, respectively. Our strategy here is also promising to be transplanted into other solar cells with similar geometric and energy band structures, helping reduce production costs and shorten the production cycle (i.e. increasing production capacity) of these photovoltaic industries.

cond-mat.mtrl-sci↗

arXiv2024

Vacancy enhanced cation ordering enables >15% efficiency in Kesterite solar cells

Atomic disorder, a widespread problem in compound crystalline materials, is a imperative affecting the performance of multi-chalcogenide Cu2ZnSn(S, Se)4 (CZTSSe) photovoltaic device known for its low cost and environmental friendliness. Cu-Zn disorder is particularly abundantly present in CZTSSe due to its extraordinarily low formation energy, having induced high-concentration deep defects and severe charge loss, while its regulation remains challenging due to the contradiction between disorder-order phase transition thermodynamics and atom-interchange kinetics. Herein, through introducing more vacancies in the CZTSSe surface, we explored a vacancy-assisted strategy to reduce the atom-interchange barrier limit to facilitate the Cu-Zn ordering kinetic process. The improvement in the Cu-Zn order degree has significantly reduced the charge loss in the device and helped us realize 15.4% (certified at 14.9%) and 13.5% efficiency (certified at 13.3%) in 0.27 cm2 and 1.1 cm2-area CZTSSe solar cells, respectively, thus bringing substantial advancement for emerging inorganic thin-film photovoltaics.

cond-mat.mtrl-sci↗

arXiv2024

Gradient bandgap enables >13% efficiency sulfide Kesterite solar cells with open-circuit voltage over 800 mV

Sulfide Kesterite Cu2ZnSnS4 (CZTS), a nontoxic and low-cost photovoltaic material, has always being facing severe charge recombination and poor carrier transport, resulting in the cell efficiency record stagnating around 11% for years. Gradient bandgap is a promising approach to relieve these issues, however, has not been effectively realized in Kesterite solar cells due to the challenges in controlling the gradient distribution of alloying elements at high temperatures. Herein, targeting at the Cd alloyed CZTS, we propose a pre-crystallization strategy to reduce the intense vertical mass transport and Cd rapid diffusion in the film growth process, thereby realizing front Cd-gradient CZTS absorber. The Cd-gradient CZTS absorber, exhibiting downward bending conduction band structure, has significantly enhanced the minority carrier transport and additionally improved band alignment and interface property of CZTS/CdS heterojunction. Ultimately, we have achieved a champion total-area efficiency of 13.5% (active-area efficiency: 14.1%) in the cell and in particular a high open-circuit voltage of >800 mV. We have also achieved a certified total-area cell efficiency of 13.16%, realizing a substantial step forward for the pure sulfide Kesterite solar cell.

cond-mat.mtrl-sci↗

arXiv2023

Defect Regulation by Palladium Incorporation towards Grain Boundaries of Kesterite solar cells

Kesterite Cu2ZnSn(S, Se)4 (CZTSSe) solar cell has emerged as one of the most promising candidates for thin-film photovoltaics. However, severe charge losses occurring at the grain boundaries (GBs) of Kesterite polycrystalline absorbers has hindered the improvement of cell performance. Herein, we report a redox reaction strategy involving palladium (Pd) to eliminate atomic vacancy defects such as VSn and VSe in GBs of the Kesterite absorbers. We demonstrate that PdSex compounds could form during the selenization process and distribute at the GBs and the absorber surfaces; thereby aid in the suppression of Sn and Se volatilization loss and inhibiting the formation of VSn and VSe defects. Furthermore, Pd(II)/Pd(IV) serves as a redox shuttle, i.e., on one hand, Pd(II) captures Se vapor from the reaction environment to produce PdSe2, on the other hand, PdSe2 provides Se atoms to the Kesterite absorber by being reduced to PdSe, thus contributing to the elimination of pre-existing VSe defects within GBs. These effects collectively reduce defects and enhance the p-type characteristics of the Kesterite absorber, leading to a significant reduction in charge recombination loss within the cell. As a result, high-performance Kesterite solar cells with a total-area efficiency of 14.5% have been achieved. This remarkable efficiency increase benefited from the redox reaction strategy offers a promising avenue for the precise regulation of defects in Kesterite solar cells and holds generally significant implications for the exploration of various other photovoltaic devices.

cond-mat.mtrl-sci↗

arXiv2023

Ni-O-Ag catalyst enables 103-m$^2$ artificial photosynthesis with >16% solar-to-chemical energy conversion efficiency

Herein, NiO nanosheets supported with Ag single atoms are synthesized for photothermal CO2 hydrogenation to achieve 1065 mmol g$^{-1}$ h$^{-1}$ of CO production rate under 1 sun irradiation, revealing the unparalleled weak sunlight driven reverse water-gas shift reaction (RWGS) activity. This performance is attributed to the coupling effect of Ag-O-Ni sites to enhance the hydrogenation of CO$_2$ and weaken the CO adsorption, resulting in 1434 mmol g$^{-1}$ h$^{-1}$ of CO yield at 300$^\circ$ C, surpassing any low-temperature RWGS performances ever reported. Building on this, we integrated the 2D Ni$_1$Ag$_{0.02}$O$_1$ supported photothermal RWGS with commercial photovoltaic electrolytic water splitting, leading to the realization of 103 m$^2$ scale artificial photosynthesis system (CO$_2$+H$_2$$\to$CO+H$_2$O) with a daily CO yield of 18.70 m$^3$, a photochemical energy conversion efficiency of >16%, over 90% H$_2$ ultilization efficiency, outperforming other types of artificial photosynthesis. The results of this research chart a promising course for designing practical, natural sunlight-driven artificial photosynthesis systems and highly efficient platinum-free CO$_2$ hydrogenation catalysts. This work is a significant step towards harnessing solar energy more efficiently and sustainably, opening exciting possibilities for future research and development in this area.

cond-mat.mtrl-sci↗

arXiv2023

Multinary Alloying Suppresses Defect Formation in Emerging Inorganic Solar Cells

The Cu2ZnSn(S, Se)4 (CZTSSe) emerging inorganic solar cell is highly promising for accelerating the large-scale and low-cost applications of thin-film photovoltaics. It possesses distinct advantages such as abundant and non-toxic constituent elements, high material stability, and excellent compatibility with industrial processes. However, CZTSSe solar cells still face challenges related to complex defects and charge losses. To overcome these limitations and improve the efficiency of CZTSSe solar cells, it is crucial to experimentally identify and mitigate deep defects. In this study, we reveal that the dominant deep defect in CZTSSe materials exhibits donor characteristics. We propose that incomplete cation exchange during the multi-step crystallization reactions of CZTSSe is the kinetics mechanism responsible for the defect formation. To address this issue, we introduce an elemental synergistic alloying approach aimed at weakening the metal-chalcogen bond strength and the stability of intermediate phases. This alloying strategy has facilitated the kinetics of cation exchange, leading to a significant reduction in charge losses within the CZTSSe absorber. As a result, we have achieved a cell efficiency of over 14.5%. These results represent a significant advancement for emerging inorganic solar cells and additionally bring more opportunities for the precise identification and regulation of defects in a wider range of multinary inorganic compounds.

cond-mat.mtrl-sci↗

arXiv2023

Heterojunction interface regulation to realize high-performance flexible Kesterite solar cells

Flexible Cu2ZnSn(S, Se)4 (CZTSSe) solar cells take the advantages of environmental friendliness, low cost, and multi-scenario applications, and have drawn extensive attention in recent years. Compared with rigid devices, the lack of alkali metal elements in the flexible substrate is the main factor limiting the performance of flexible CZTSSe solar cells. This work proposes a Rb ion additive strategy to simultaneously regulate the CZTSSe film surface properties and the CdS chemical bath deposition (CBD) processes. Material and chemical characterization reveals that Rb ions can passivate the detrimental Se0 cluster defect and additionally provide a more active surface for the CdS epitaxial growth. Furthermore, Rb can also coordinate with thiourea (TU) in the CBD solution and improve the ion-by-ion deposition of the CdS layer. Finally, the flexible CZTSSe cell fabricated by this strategy has reached a high total-area efficiency of 12.63% (active-area efficiency of 13.2%), with its VOC and FF reaching 538 mV and 0.70, respectively. This work enriches the alkali metal passivation strategies and provides new ideas for further improving flexible CZTSSe solar cells in the future.

physics.app-ph↗

arXiv2023

Controlling selenization equilibrium enables high-quality Cu2ZnSn(S, Se)4 absorbers for efficient solar cells

Cu2ZnSn(S, Se)4 (CZTSSe) is one of most competitive photovoltaic materials for its earth-abundant reserves, environmental friendliness, and high stability.The quality of CZTSSe absorber determines the power-conversion efficiency (PCE) of CZTSSe solar cells. The absorber's quality lies on post-selenization process, which is the reaction of Cu-Zn-Sn precursor and selenium vapor. And the post-selenization is dependent on various factors (e.g. temperature, precursor composition, reaction atmosphere, etc).However, synergistic regulation of these factors cannot be realized under a widely-used single-temperature zone selenization condition.Here, in our dual-temperature zone selenization scheme, a solid-liquid and solid-gas (solid precursor and liquid/gas phase Se) synergistic reaction strategy has been developed to precisely regulate the selenization. Pre-deposited excess liquid Se provides high Se chemical potential to drive a direct and fast formation of the CZTSSe phase, significantly reducing the amount of binary and ternary compounds within phase evolution. And organics removal can be accomplished via a synergistic optimization of Se condensation and subsequent volatilization. We achieve a high-performance CZTSSe solar cell with a remarkable PCE of 13.6%, and the highest large-area PCE of 12.0% (over 1cm2). Our strategy will provide a new idea for further improving efficiency of CZTSSe solar cells via phase evolution regulation, and also for other complicated multi-compound synthesis.

cond-mat.mtrl-sci↗

arXiv2022

A precisely regulating phase evolution strategy for highly efficient kesterite solar cells

Phase evolution during the selenization is crucial for high-quality kesterite Cu2ZnSn(S, Se)4 (CZTSSe) absorbers and efficient solar cells. Herein, we regulate kinetic process of phase evolution from Cu+-Sn4+-MOE (MOE: 2-methoxyethanol) system by precisely controlling positive chamber pressure. We found that, at the heating-up stage, Se vapor concentration is intentionally suppressed in low-temperature region, which effectively reduces collision probability between the CZTS and Se atoms, thus remarkably inhibiting formation of secondary phases on the surface and multiple-step phase evolution processes. This strategy enables the phase evolution to start at relatively higher temperature and thereby leading to high crystalline quality CZTSSe absorber with fewer defects, and corresponding CZTSSe solar cell can present 14.1% efficiency (total area), which is the highest result so far. This work provides important insights into selenization mechanism of CZTSSe absorbers and explores a new way of kinetic regulation strategy to simplify the phase evolution path to efficient CZTSSe solar cells.

cond-mat.mtrl-sci↗

arXiv2022

Efficient Extraction of Hot Carriers in Perovskite Quantum Dot through Building State Coupled Complex

Utilizing hot carriers is the crucial approach for solar cell to exceed the thermodynamic detailed balance limit, yet effective extraction of hot carriers in absorber materials via most commonly used semiconductor acceptors has been a challenge in both materials and photophysics research for many years. Herein, we build series of CsPbI3 quantum dot and fullerene derivative systems to explore the decisive factors of this process and have for the first time realized efficient hot carrier extraction in these systems (maximum extraction efficiency ~ 84%). We find building the systems as state-coupled complexes creates new carrier transport channels at about 0.22 eV above CsPbI3 quantum dot bandgap, which facilitates highly efficient HC extraction. Our research directly visualizes the inner connection of molecule interaction and ultrafast hot carrier extraction. The knowledge and strategy gained here are of universal meaning, taking an important step forward true hot carrier photovoltaics.

physics.app-ph↗

arXiv2022

Spontaneous Radiative Cooling to Enhance the Operational Stability of Perovskite Solar Cells via a Black-body-like Full Carbon Electrode

Operational stability of perovskite solar cells is remarkably influenced by the device temperature, therefore, decreasing the interior temperature of the device is one of the most effective approaches to prolong the service life. Herein, we introduce the spontaneous radiative cooling effect into the perovskite solar cell and amplified this effect via functional structure design of a full-carbon electrode (F-CE). Firstly, with interface engineering, >19% and >23% power conversion efficiencies of F-CE based inorganic CsPbI3 and hybrid perovskite solar cells have been achieved, respectively, both of which are the highest reported efficiencies based on carbon electrode and are comparative to the results for metal electrodes. Highly efficient thermal radiation of this F-CE can reduce the temperature of the operating cell by about 10 °C. Compared with the conventional metal electrode-based control cells, the operational stability of the above two types of cells have been significantly improved due to this cooling effect. Especially, the CsPbI3 PSCs exhibited no efficiency degradation after 2000 hours of continuous operational tracking.

physics.app-ph↗

arXiv2022

A new artificial photosynthetic system coupling photovoltaic electrocatalysis with photothermal catalysis

In this work, we present a novel artificial photosynthetic paradigm with square meter (m2) level scalable production by integrating photovoltaic electrolytic water splitting device and solar heating CO2 hydrogenation device, successfully achieving the synergy of 1 sun driven 19.4% solar to chemical energy efficiency (STC) for CO production (2.7 times higher than state of the art of large-sized artificial photosynthetic systems) with a low cost (equivalent to 1/7 of reported artificial photosynthetic systems). Furthermore, the outdoor artificial photosynthetic demonstration with 1.268 m2 of scale exhibits the CO generation amount of 258.4 L per day, the STC of ~15.5% for CO production in winter, which could recover the cost within 833 suuny days of operation by selling CO.

physics.app-ph↗

arXiv2020

Eliminating the Electric Field Response in a Perovskite Heterojunction Solar Cell to Improve Operational Stability

Intrinsic and extrinsic ion migration is a very large threat to the operational stability of perovskite solar cells and is difficult to completely eliminate due to the low activation energy of ion migration and the existence of internal electric field. We propose a heterojunction route to help suppress ion migration, thus improving the operational stability of the cell from the perspective of eliminating the electric field response in the perovskite absorber. A heavily doped p-type (p+) thin layer semiconductor is introduced between the electron transporting layer (ETL) and perovskite absorber. The heterojunction charge depletion and electric field are limited to the ETL and p+ layers, while the perovskite absorber and hole transporting layer remain neutral. The p+ layer has a variety of candidate materials and is tolerant of defect density and carrier mobility, which makes this heterojunction route highly feasible and promising for use in practical applications.

physics.app-ph↗

arXiv2019

Coordination Engineering of Cu-Zn-Sn-S Aqueous Precursor for Efficient Kesterite Solar Cells

Aqueous precursors provide an alluring approach for low-cost and environmentally friendly production of earth-abundant Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. The key is to find an appropriate molecular agent to prepare a stable solution and optimize the coordination structure to facilitate the subsequent crystallization process. Herein, we introduce thioglycolic acid, which possesses strong coordination (-SH) and hydrophilic (-COOH) groups, as the agent and use deprotonation to regulate the coordination competition within the aqueous solution. Ultimately, metal cations are adequately coordinated with thiolate anions, and carboxylate anions are released to become hydrated to form an ultrastable aqueous solution. These factors have contributed to achieving CZTSSe solar cells with efficiency of as high as 12.2% (a certified efficiency of 12.0%) and providing an extremely wide time window for precursor storage and usage. This work represents significant progress in the non-toxic solution fabrication of CZTSSe solar cells and holds great potential for the development of CZTSSe and other metal sulfide solar cells.

physics.app-ph↗

arXiv2019

Exploiting Electrical Transients to Reveal Charge Loss Mechanism of Junction Solar Cells

Electrical transients enabled by optical excitation and electric detection provide a distinctive opportunity to study the charge transport, recombination and even the hysteresis of a solar cell in a much wider time window ranging from nanoseconds to seconds. However, controversies on how to exploit these investigations to unravel the charge loss mechanism of the cell have been ongoing. Herein, a new methodology of quantifying the charge loss within the bulk absorber or at the interfaces and the defect properties of junction solar cells has been proposed after the conventional tail-state framework is firstly demonstrated to be unreasonable. This methodology has been successfully applied in the study of commercialized silicon and emerging Cu2ZnSn(S, Se)4 and perovskite solar cells herein and should be universal to other photovoltaic device systems with similar structures. Overall, this work provides an alluring route for comprehensive investigation of dynamic physics processes and charge loss mechanism of junction solar cells and possesses potential applications for other optoelectronic devices.

physics.app-ph↗

arXiv2019

Clearly Discriminate the Continuum Band and Exciton State of the Hybrid Lead Bromide Perovskite

Electronic states of the hybrid perovskite enable their promising applications as distinctive optoelectronic materials. The understanding of their electronic structures and charge characters remains highly controversial. The electronic mechanism such as reabsorption, Urbach tail and indirect band for interpreting dual-peak emissions is one of the controversial focuses. Herein, we report that through heterojunction enhanced exciton dissociation and global tracing of multiple radiative electronic states across wide temperature regions, we have succeeded in directly observing free carrier emissions from the hybrid lead bromide perovskite and clearly discriminating the direct continuum band and exciton states. The widely-concerned dual-peak emissions are clarified to be excitonic, arising from two types of exciton states of the perovskite. These excitons possess giant binding energies and superior phase stability compared to conventional inorganic semiconductors, providing important implications for exploiting the excitonic mechanism for realizing novel optoelectronic applications.

physics.app-ph↗

arXiv2019

Low-threshold Stimulated Emission of Hybrid Perovskites at Room Temperature through Defect-Mediated Bound Excitons

Excitonic stimulated emission provides a promising mechanism and route to achieve low-threshold semiconductor lasers for micro-nano optoelectronic integrations. However, excitonic stimulated emission from quantum structure-free semiconductors has rarely been realised at room temperature due to the phase transition between excitonic and electron-hole plasma states. Herein, we show that through trap-state and band-edge engineering, bound exciton states can be stabilised within the hybrid lead bromide perovskite. Under modest pumping conditions, these states enable stimulated emission behaviour that exhibits a low threshold carrier density of only 1.6*1017 cm-3, as well as a high peak gain coefficient of ~1300 cm-1. This is the first time that bound exciton stimulated emission has been realised at room temperature from a quantum structure-free semiconductor. Not only does this open up new research horizons for perovskite materials, but also it has important implications for semiconductor excitonic physics and the development of next-generation optoelectronic applications.

physics.app-ph↗