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Correlation of afterglow, trap states and site preference in RE2O3:1%Eu (RE=Lu, Y, Sc) single crystal scintillators
摘要： RE2O3:1%Eu (RE=Lu, Y, Sc) single crystals were grown by the optical floating zone method. Correlated measurements of afterglow curves, thermoluminescence, photoluminescence decay, and radioluminescence curves were performed. It is found that the afterglow intensity of Sc2O3:Eu is much lower than the other two compounds and Y2O3:Eu presents a slightly lower afterglow intensity than Lu2O3:Eu. It is discussed in the light of the influence of trap states and site preference in the RE2O3:Eu. The afterglow difference between Sc2O3:Eu and other two compounds mainly comes from the disappearance of Schottky defect in Sc2O3:Eu. While the afterglow difference between Y2O3:Eu and Lu2O3:Eu probably ascribes to the lower S6 site ratio in Y2O3:Eu. Their photoluminescence and other radioluminescence properties were also measured and compared.
关键词： afterglow,trap state,RE2O3:Eu,site preference
更新于2025-09-23 15:23:52
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Surface Passivation of Perovskite Film by Sodium Toluenesulfonate for Highly Efficient Solar Cells
摘要： Ionic defects at the surfaces of organolead halide perovskite films are detrimental to both the efficiency and stability of perovskite solar cells (PSCs). Herein, sodium p-toluenesulfonate (STS) is applied during the surface modification of perovskite layer for the first time, leading to the efficient surface passivation of the perovskite film and consequently significant enhancements in both efficiency and stability of mixed-cation PSC devices. Upon incorporating STS atop the perovskite layer, the power conversion efficiency of the Cs0.05MA0.12FA0.83PbI2.55Br0.45 (abbreviated as CsMAFA) mesoporous-structure mixed-cation PSC devices improves from 18.70% to 20.05% with reduced hysteresis. The sulfonate (–SO3–) anion of STS coordinates with the Pb2+ of CsMAFA perovskite, and the Na+ cation of STS electrostatically interacts with the anions (I–/Br–) of CsMAFA perovskite, resulting in the surface passivation of the CsMAFA perovskite film with reduced electron and hole trap state densities. In addition, STS modification induces an upshift of the valence band of perovskite, facilitating hole extraction from the perovskite layer to the hole transport layer with suppressed interfacial charge recombination. Moreover, such a trap state passivation of perovskite film leads to improvement of the ambient stability of PSC devices.
关键词： ionic defects,trap state passivations,perovskite solar cells,surface modifications,charge extractions
更新于2025-09-23 15:21:01
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Facet Control for Trap-State Suppression in Colloidal Quantum Dot Solids
摘要： Trap states in colloidal quantum dot (QD) solids significantly affect the performance of QD solar cells, because they limit the open-circuit voltage and short circuit current. The {100} facets of PbS QDs are important origins of trap states due to their weak or missing passivation. However, previous investigations focused on synthesis, ligand exchange, or passivation approaches and ignored the control of {100} facets for a given dot size. Herein, trap states are suppressed from the source via facet control of PbS QDs. The {100} facets of ≈3 nm PbS QDs are minimized by tuning the balance between the growth kinetics and thermodynamics in the synthesis. The PbS QDs synthesized at a relatively low temperature with a high oversaturation follow a kinetics-dominated growth, producing nearly octahedral nanoparticles terminated mostly by {111} facets. In contrast, the PbS QDs synthesized at a relatively high temperature follow a thermodynamics-dominated growth. Thus, a spherical shape is preferred, producing truncated octahedral nanoparticles with more {100} facets. Compared to PbS QDs from thermodynamics-dominated growth, the PbS QDs with less {100} facets show fewer trap states in the QD solids, leading to a better photovoltaic device performance with a power conversion efficiency of 11.5%.
关键词： solar cells,trap-state suppression,quantum dots,facet control
更新于2025-09-23 15:21:01
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The influence of the electron transport layer on charge dynamics and trap-state properties in planar perovskite solar cells
摘要： Despite the outstanding photovoltaic performance of perovskite solar cells, the correlation between the electron transport layer and the mechanism of photoelectric conversion is still not fully understood. In this paper, the relationship between photovoltaic performance and carrier dynamics is systematically studied in both TiO2- and SnO2-based planar perovskite devices. It is found that the different electron transport layers result in distinct forward scan results and charge dynamics. Based on the charge dynamics results, the influence of the electron transport layer on charge carrier transport and charge recombination is revealed. More importantly, the trap-state density is characterized, which is proven to be related to the charge carrier dynamics and the specific hysteresis behaviour in the perovskite solar cells. The present work would provide new insights into the working mechanisms of electron transport layers and their effect on hysteresis.
关键词： electron transport layer,hysteresis,charge dynamics,perovskite solar cells,trap-state properties
更新于2025-09-23 15:19:57
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Effect of thioglycolic acid molecules on luminescence properties of $$\hbox {Ag}_2$$Ag2S quantum dots
摘要： For monoclinic Ag2S nanocrystals (quantum dots, Ag2S/TGA QDs), the correlation between their luminescence properties and aspects of their passivation by thioglycolic acid (TGA) molecules is considered. The features of quantum confinement effect in the QDs absorption and photoluminescence spectra are analyzed for Ag2S QDs with an average size of 1.7–3.1 nm. We show that, in various conditions of passivation of QDs interfaces, the luminescence mechanism of Ag2S/TGA QDs is switched from recombination luminescence in the 870–1000 nm region to exciton luminescence with a band maximum at 620 nm. By means of FTIR spectra, two major types of interactions between TGA molecules and Ag2S QDs, arising due to changing the [Ag+]:[S2?] ratio from 1:0.9 to 1:1.43, are determined. Exciton luminescence (620 nm) occurs in case of using TGA as the sulfur source in Ag2S crystallization and the interface passivation agent, with [Ag+]:[S2?] = 1:1. The analysis of the FTIR spectra indicates bonding of TGA with the Ag2S surface by both thiol and carboxylic groups in this case. With increasing the sulfur concentration in the synthesis of Ag2S/TGA QDs, the exciton luminescence is suppressed. The employment of Na2S as the sulfur source in Ag2S crystallization with TGA acting as the surface passivation agent promotes the formation of recombination centers for IR luminescence. In this case, analysis of the FTIR spectra indicates passivation of Ag2S QDs by TGA molecules due to adsorption of thiol groups. It is found that the photodegradation or IR luminescence of Ag2S/TGA QDs upon exposure to exciting radiation is due to the photolysis of Ag2S nanocrystals with formation of luminescence quenching centers as well as due to photodestruction of TGA molecules.
关键词： Size dependence,Thioglycolic acid,Interaction mechanism,FTIR spectra,Trap state luminescence,Silver sulfide,Luminescence properties
更新于2025-09-23 15:19:57
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Colloidal Synthesis and Charge-Carrier Dynamics of Cs2AgSb1-yBiyX6 (X: Br, Cl; 0 ≤y ≤ 1) Double Perovskite Nanocrystals
摘要： A series of lead-free double perovskite NCs: Cs2AgSb1-yBiyX6 (X: Br, Cl; 0≤y≤1) NCs are synthesized. In particular, Cs2AgSbBr6 NCs is a new double perovskite material that has not been reported for the bulk form. Mixed Ag-Sb/Bi NCs exhibit enhanced stability in colloidal solution compared to Ag-Bi or Ag-Sb NCs. Femtosecond transient absorption studies indicate the presence of two prominent fast trapping processes in the charge carrier relaxation. The two fast trapping processes are dominated by intrinsic self-trapping (1~2 ps) due to giant exciton-phonon coupling and surface defects trapping (50~100 ps), respectively. Slow hot-carrier relaxation is observed at high pump fluence, and the possible mechanisms for the slow hot-carrier relaxation are also discussed.
关键词： nanocrystal,double perovskite,carrier-phonon coupling,hot-carrier cooling,trap state
更新于2025-09-23 15:19:57
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Colloidal Synthesis and Charge-Carrier Dynamics of Cs2AgSb1-yBiyX6 (X: Br, Cl; 0 ≤y ≤ 1) Double Perovskite Nanocrystals
摘要： A series of lead-free double perovskite NCs: Cs2AgSb1-yBiyX6 (X: Br, Cl; 0≤y≤1) NCs are synthesized. In particular, Cs2AgSbBr6 NCs is a new double perovskite material that has not been reported for the bulk form. Mixed Ag-Sb/Bi NCs exhibit enhanced stability in colloidal solution compared to Ag-Bi or Ag-Sb NCs. Femtosecond transient absorption studies indicate the presence of two prominent fast trapping processes in the charge carrier relaxation. The two fast trapping processes are dominated by intrinsic self-trapping (1~2 ps) due to giant exciton-phonon coupling and surface defects trapping (50~100 ps), respectively. Slow hot-carrier relaxation is observed at high pump fluence, and the possible mechanisms for the slow hot-carrier relaxation are also discussed.
关键词： nanocrystal,double perovskite,carrier-phonon coupling,hot-carrier cooling,trap state
更新于2025-09-23 15:19:57
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Alleviation of abnormal NBTI phenomenon in LTPS TFTs on polyimide substrate for flexible AMOLED
摘要： This letter investigates the negative-bias temperature instability (NBTI) behavior of p-channel low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs) on plastic substrate. The measurements reveal that the threshold-voltage positive shift is highly correlated to the passivation of grain boundary trap states. By applying the established phenomenon such as NBTI recovery and H diffusion from PI substrate, a new model is introduced to explain the mechanism and verified by the experiment. With the thick buffer and bottom metal layer or newly processed PI substrate, we succeeded in adjusting the NBTI behavior of LTPS TFTs on plastic substrate.
关键词： interface trap state,flexible AMOLED,negative-bias temperature instability (NBTI),grain boundary trap state,LTPS TFTs
更新于2025-09-19 17:13:59
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High-Efficiency Nonfullerene Organic Solar Cells Enabled by 1000 nm Thick Active Layers with a Low Trap-State Density
摘要： The high-efficient organic solar cells (OSCs) with thicker active layers are potential candidates for large-area solar panels fabrication. The low charge carrier mobility of the photoactive materials has been identified as the major problem hindering photovoltaic performance of the thick-film OSCs. In this study, high performance of ultra-thick film organic solar cells employing a non-fullerene acceptor BTP-4Cl and a polymer donor PBDB-TF is demonstrated. Two blends (PBDB-TF:BTP-4Cl and PBDB-TF:IT-4F) show comparable mobilities and excellent photovoltaic characteristics in thin-film devices; while in the 1000-nm-thick devices, although they both exhibit desirable and balanced mobilities, the PBDB-TF:BTP-4Cl-based blend possesses lower trap-state density than the IT-4F-based counterpart, leading to lower trap-assist recombination, longer carrier lifetime, and thus a much higher short circuit current density in the device. As a result, the BTP-4Cl-based 1000-nm-thick OSC achieves a remarkable PCE of 12.1%, which greatly outperforms the IT-4F-based devices (4.72%). What is more, for a 1000-nm thick device with active area of 4 cm2, a promising efficiency of 10.1% was obtained, showing its great potential in future large-scale production.
关键词： trap-state density,ultra-thick active layers,high efficiency,non-fullerene organic solar cells,charge carrier mobility
更新于2025-09-19 17:13:59