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On the origin of the enhancement of defect related visible emission in annealed ZnO micropods
摘要： We report an in-depth analysis of ZnO micropods emission. A strong correlation between defect and interband emissions is observed. ZnO micropods were grown using low-temperature chemical bath deposition (CBD). ZnO micropods exhibited perfectly-crystalline hexagonally-shaped facets with various numbers of branches. Raman studies showed that ZnO micropods contained trapped zinc hydroxide (OH) and imidogen (NH) defects that originate from the precursor solution used in the CBD technique. These defects were evacuated by thermal annealing, leading to the recrystallization in the volume of the micropods and the formation of structural defects at their surface, as attested by scanning electron microscopy and X-ray diffraction. More importantly, the thermal annealing was accompanied by a breakdown of the NH defects, which resulted in a nitrogen doping of the ZnO micropods. The structural changes as well as the nitrogen doping resulted in a drastic change in the photoluminescence (PL) spectrum of the ZnO micropods that exhibited a stronger free exciton UV emission as well as a stronger visible (white) emission. An in-depth low-temperature PL study of both UV and visible emission reveals a strong interplay between the structural-defect bound excitonic UV emission (Y-band) and the deep donor (visible) emission, which suggests a rather complex emission mechanism involving an efficient nonradiative energy transfer between the Y-band states and defect states leading to the enhanced visible emission of ZnO micropods after high temperature annealing.
关键词： nitrogen doping,chemical bath deposition,photoluminescence,ZnO micropods,thermal annealing,defect emission
更新于2025-09-16 10:30:52
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Rapid fabrication of perovskite solar cells through intense pulse light annealing of SnO2 and triple cation perovskite thin films
摘要： Rapid evolution of perovskite solar cells (PSCs) performance and stability has inclined the research focus towards scalable bulk fabrication through high speed and cost-effective automated methods. For the first time, intense pulsed light (IPL) is utilized to rapidly fabricate efficient PSCs through swift annealing of both the SnO2 electron transport layer (ETL) and mixed triple cation perovskite thin films. The addition of di-iodomethane (CH2I2) alkyl-halide could enhance the PSC efficiency by retarding the crystallization and improving the surface morphology of the perovskite photoactive film through supplying iodine cleaved by ultraviolet energy during IPL process. The maximum efficiency and fill factor of the PSCs fabricated by IPL annealing were 12.56% and 78.3% for the rigid glass-FTO slides, and 7.6% and 64.75% for flexible PET-ITO substrates when processed in the ambient with relative humidity of 60%, respectively. The annealed materials were characterized through Scanning electron microscopy (SEM), UV-vis, photoluminescence (PL), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. In addition, impedance spectroscopy (IS) and current-voltage measurements were conducted to study the functionality of fabricated cells. Our results delineated the feasibility of sequential step IPL annealing on rapid fabrication of efficient PSCs which is directly applicable for scalable roll-to-roll manufacturing.
关键词： Di-iodomethane,SnO2,Rapid thermal annealing,Intense pulse light,Perovskite solar cell
更新于2025-09-16 10:30:52
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Mechanism of Organic Solar Cell Performance Degradation upon Thermal Annealing of MoO <sub/>x</sub>
摘要： In this work we focus on P3HT:PC61BM bulk heterojunction (BHJ) devices with MoO3 at the hole extraction side of the BHJ which relies on the formation of a strong dipole at the BHJ/MoO3 interface, as a reference system that has been extensively studied. We have observed depending on when the annealing is performed during device fabrication, device performance either increased or decreased due to formation of a sharp or relatively diffuse interface respectively due to diffusion of MoOx into the BHJ. The measured strength of the dipole at this interface following thermal annealing correlated well with the width of the interface and device performance, with the sharper interface resulting in a stronger dipole and in improved device performance. This is expected to be a general phenomenon for evaporated coatings onto polymeric BHJ, regardless of the polymers involved.
关键词： Organic solar cell,Interface dipole,MoO3,Thermal annealing,Energy level alignment
更新于2025-09-12 10:27:22
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Studying the Effect of Doping with Nickel on Silicon-Based Solar Cells with a Deep p–n-Junction
摘要： It has been shown that the doping of the front side of a solar cell with a deep-level p–n junction with nickel atoms increases short-circuit current density Jsc by 89% and open-circuit voltage Voc by 19.7%. Additional thermal treatment at 700°C for 1 h increases Jsc by 98.4% and Voc by 13.18%. It is presumed that the IR radiation conversion efficiency grows because nickel atoms form clusters, these being getter centers for uncontrolled recombinant impurities.
关键词： photocell,silicon,nickel,lifetime,collection coefficient,thermal annealing,clusters,doping
更新于2025-09-12 10:27:22
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Theoretical correlation and effect of annealing on the photoresponse of vertically strain-coupled In <sub/>0.5</sub> Ga <sub/>0.5</sub> As/GaAs quantum dot heterostructures
摘要： Here, we propose a di?erent approach for growing strain-coupled In0.5Ga0.5As quantum dot infrared photodetectors (QDIPs) with varying dot layer periodicity. Strain calculation is done throughout the quantum dot (QD) heterostructures, which has a signi?cant e?ect on the carrier probability density functions. The localization of the electron probability density function in each heterostructure has a strong correlation with the photoresponse. The con?ned electron wavefunction in the top QD layer of the optimized device heterostructure (trilayer QDIP having dot layer periodicity of three) would be useful for hyperspectral imaging applications owing to its narrow (8.67 meV) photoresponse. Rapid thermal annealing treatment was carried out on the trilayer QDIP to investigate the enhancement in its optoelectronic properties. The dark current density reduced by two orders, and the operating temperature increased by 30 °C for the 650 °C-annealed counterpart. Also, the responsivity enhanced by two times (2.05 A/W at ?1 V) for the annealed QDIP.
关键词： In0.5Ga0.5As,rapid thermal annealing,photoresponse,strain-coupled,quantum dot infrared photodetectors
更新于2025-09-12 10:27:22
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Influences of Energetically Controlled Dielectric Functionality on Polymer Field-Effect Transistor Performance
摘要： We systematically demonstrated the effects of surface modification of gate dielectrics and the thermal annealing of an ad-deposited polymer semiconducting film on the electrical performance of organic field-effect transistors (OFETs) in which they were incorporated. Chemically or energetically engineered dielectrics were designed by introducing various end-functional groups (CF3, CH3, NH2, Cl, and SH). Poly(dioctyl-quaterthiophene-dioctyl-bithiazole) (PDQDB), consisting of 5,5 ′ -bithiazole and oligothiophene rings, was employed as the polymer semiconductor. We analyzed the PDQDB semiconducting films’ crystalline character, which has an important effect on the FET performance, and confirmed that the crystallinity of the PDQDB semiconducting films was higher in the cases (CF3 and CH3) of low surface energy than in the cases (NH2, SH, and Cl) of high surface energy, yielding μFET values as high as 0.13 and 0.12 cm2 V?1 s?1 for the CF3 and CH3 cases, respectively. Another important observation was the tendency of the μFET value to change depending on the thermal annealing temperature—increasing and decreasing in the cases of surface functionalities with low and high surface energies, respectively. These results could be interpreted on the basis of the differently competitive molecule–molecule and molecule–dielectric surface interactions, where the π–π stacking configuration of the conjugated molecular structures was enhanced on lower-energy surfaces. We also discussed the effect of permanent dipoles for the engineered self-assembled monolayer dielectrics on the threshold and turn-on voltages in the PDQDB FET devices.
关键词： thermal annealing,surface modification,polymer semiconductor,organic field-effect transistors,dielectric functionality
更新于2025-09-12 10:27:22
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Efficient non-fullerene polymer solar cells enabled by side-chain conjugated thieno[3,4-c]pyrrole-4,6-dione-based polymer and small molecular acceptors
摘要： The application of non-fullerene (NF) acceptors in bulk-heterojunction (BHJ) polymer solar cells (PSCs) is a promising approach to overcome the inherent drawbacks of fullerene derivatives-based acceptors. In PSCs, complementary absorption as well as matched molecular energy levels between the low bandgap acceptor-donor-acceptor (A-D-A) small molecular acceptor and medium/wide bandgap polymer donor is crucial to achieve high power conversion efficiency (PCE). Alternating polymers based on benzodithiophene (BDT) electron-donating segment and thieno[3,4-c]pyrrole-4,6-dione (TPD) electron-withdrawing segment own medium bandgap and low-lying highest occupied molecular orbital (HOMO) energy level, leading to presentable photovoltaic properties with fullerene derivatives. To probe into the performances of TPD-based polymers in NF-PSCs, two TPD-based polymers containing alkoxy or alkylthienyl modified benzo[1,2-b:4,5-b′]dithiophene (BDT) were synthesized and adopted as electron-donors and blended with A-D-A-type electron-acceptor 2,2′-[[6,6,12,12-tetrakis(4-hexylphenyl)-s-indacenodithieno[3,2-b]thiophene]methylidyne(3-oxo-1H-indene-2,1(3H)-diylidene)]]bis(propanedinitrile) (ITIC) to fabricate the corresponding photovoltaic devices. The two-dimensional conjugated polymer PBDTT-TPD shows enhanced extinction coefficient, deeper HOMO energy level and better hole transport performance, resulting in improved PCE of 6.17%. To further boost the performances of the polymers, a small molecular acceptor 2,2′-((2Z,2′Z)-((4,4,9,9-tetrahexyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-2,7-diyl) bis(methanylylidene))bis(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (IDIC) with down-shifted energy level was also used to blend with the two polymers in PSCs. Despite the open-circuit voltage (VOC) of the PBDTT-TPD:IDIC-based device is slightly decreased, the short-circuit current density (JSC) and fill factor (FF) are simultaneously improved, yielding an promising PCE of 7.15%. These results indicate that two-dimensional conjugated TPD-based polymers can be potential application as medium bandgap polymeric donor to match with small molecular acceptors having suitable molecular energy levels to get high efficiency in PSCs.
关键词： Non-fullerene acceptors,Thieno[3,4-c]pyrrole-4,6-dione,Energy level offsets,Polymer solar cells,Thermal annealing
更新于2025-09-11 14:15:04
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Postannealed Structural Relaxation and Phase Evolution of Quaternary Alloy BeMgZnO
摘要： The thermal stability of quaternary alloy BeMgZnO was investigated in this study. When a Be0.09Mg0.19Zn0.72O alloy film was annealed, structural relaxation and reconstruction of the film layers were found at 600, 700, and 800 °C. Be atoms were found to gradually diffuse out from the host lattice, and Mg atoms were still maintained. As a result, a mixed-phase alloy containing BeO and MgxZn1?xO was continuously generated. Correspondingly, the bandgap of Be0.09Mg0.19Zn0.72O reduced because of the diffusion of Be atoms. Hence, the thermodynamic solubility of BeO in ZnO and MgO was demonstrated to be relatively low. Additionally, the aging effect caused by a higher annealing temperature is more effective than that caused by a lower annealing temperature for a longer time. Due to the improvement of crystal quality, an MSM interdigital structure photodetector based on the 800 °C annealed sample was fabricated and revealed a strong response to the UV light. Our finding provides a new understanding of the ultrawide bandgap quaternary alloy BeMgZnO and contributes to a significant step toward its practical applications.
关键词： bandgap,photodetector,Be diffusion,BeMgZnO,thermal annealing,structural relaxation
更新于2025-09-11 14:15:04
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Regional Band‐Gap Tailoring of 1550nm‐band InAs Quantum Dot Intermixing by Controlling Ion Implantation Depth
摘要： The regional control of the band-gap energies using the highly-stacked quantum dot (QD) on InP (311)B substrate changing ion implantation depths in the process of the quantum dot intermixing (QDI) technique is investigated. The QDI process involves B+ implantation and rapid thermal annealing (RTA) around 600 °C, in which the ion implantation depths are controlled regionally with a combination of SiO2 and polymer (AZ) films. Controlled blue shifts of the photoluminescence (PL) spectra verify the effectiveness of the regionally controlled QDI process for application to semiconductor photonic integrated circuits using 1550nm-band QD such as integrated WDM light sources.
关键词： rapid thermal annealing,intermixing,ion implantation,quantum dot
更新于2025-09-11 14:15:04
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Effect of Electron-Acceptor Content on the Efficiency of Regioregular Double-Cable Thiophene Copolymers in Single-Material Organic Solar Cells
摘要： Three regioregular thiophenic copolymers, characterized by a bromine atom or a C60-fullerene group at different molar ratios at the end of a decamethylenic plastifying side chain, have been successfully synthesized using a straightforward postpolymerization functionalization procedure based on a Grignard coupling reaction. Owing to their good solubility in common organic solvents, the products were fully characterized using chromatographic, spectroscopic, thermal, and morphological techniques and used as single materials in the photoactive layers of organic solar cells. The photoconversion efficiencies obtained with copolymers were compared with those of a reference cell prepared using a physical blend of the precursor homopolymer and [6,6]-phenyl-C61-butyric acid methyl ester. The best results were obtained with COP2, the copolymer with a 21% molar content of C60-functionalized side chains. The use of the double-cable polymer made possible an enhanced control on the nanomorphology of the active blend, thus reducing phase-segregation phenomena as well as the macroscale separation between the electron-acceptor and -donor components, yielding a power conversion efficiency higher than that of the reference cell (4.05 vs 3.68%). Moreover, the presence of the halogen group was exploited for the photo-cross-linking of the active layer immediately after the thermal annealing procedure. The cross-linked samples showed an increased stability over time, leading to good efficiencies even after 120 h of accelerated aging: this was a key feature for the widespread practical applicability of the prepared devices.
关键词： photo-cross-linking,C60-fullerene,double-cable polymer,thermal annealing,regioregular thiophenic copolymers,Grignard coupling reaction,organic solar cells,photoconversion efficiencies
更新于2025-09-11 14:15:04