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Thienyl Sidechain Substitution and Backbone Fluorination of Benzodithiophene-Based Donor Polymers Concertedly Minimize Carrier Losses in ITIC-Based Organic Solar Cells
摘要： Non-fullerene acceptor (NFA) based organic solar cells have outperformed fullerene-based devices, yet their photophysics is less well understood. Herein, changes in the donor polymer backbone side-chain substitution and backbone fluorination in benzodithiophene (BDT)-thiophene copolymers are linked to the photophysical processes and performance of bulk heterojunction (BHJ) solar cells, using ITIC as NFA. Increased geminate recombination is observed when the donor polymer is alkoxy-substituted in conjunction with faster non-geminate recombination of free charges, limiting both the short circuit current and device fill factor. In contrast, thienyl-substitution reduces geminate recombination, albeit non-geminate recombination remains significant, leading to improved short circuit current density, yet not fill factor. Only the combination of thienyl-substitution and polymer backbone fluorination yields both efficient charge separation and significantly reduced non-geminate recombination, resulting in fill factors (FFs) in excess of 60 %. Time-delayed collection field measurements ascertain that charge generation is field-independent in the thienyl-substituted donor polymer:ITIC systems, while weakly field dependent in the alkoxy-substitued polymer:ITIC blend, indicating the low FFs are primarily caused by non-geminate recombination. This work provides insight into the interplay of donor polymer structure, BHJ photophysics, and device performance for a prototypical NFA, namely ITIC. More specifically, it links the donor polymer chemical structure to quantifiable changes of kinetic parameters and the yield of individual processes in ITIC-based BHJ blends.
关键词： non-fullerene acceptor,ultrafast spectroscopy,bulk heterojunction,charge generation,organic photovoltaics
更新于2025-09-23 15:19:57
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Self-Powered Filterless Narrow-Band pa??n Heterojunction Photodetector for Low Background Limited Near-Infrared Image Sensor Application
摘要： Photonic detection with narrow spectrum selectivity is very important to eliminate the signal from obtrusive light, which can improve the anti-interference ability of the infrared imaging system. While self-driving effect inherent to p-n junction is very attractive in optic-electronic integration, the application of p-n junction in narrow-band photodetector is limited by the usual broad absorption range. In this work, a self-powered filterless narrowband near-infrared photodetector based on CuGaTe2/silicon p-n junction was reported. The as-fabricated photodetector exhibited typical narrow-band response which shall be ascribed to the slightly smaller bandgap of Si than CuGaTe2 and the restricted photocurrent generation region in the p-n heterojunction by optimizing CuGaTe2 thickness. It is observed that when the thickness of CuGaTe2 film is 143 nm, the device exhibits a response peak centered around 1050 nm with a full-width at half-maximum of ~118 nm. Further device analysis reveals a specific detectivity of ~1012 Jones and a responsivity of 114 mA/W under 1064 nm illumination at zero bias. It was also found that image system based on the narrowband CuGaTe2/Si photodetector showed high noise immunity for its spectral selective characteristics.
关键词： p-n heterojunction,near infrared light,image sensing,spectral selectivity,narrow band photodetector
更新于2025-09-23 15:19:57
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New energetic indandione based planar donor for stable and efficient organic solar cells
摘要： The present work documents the synthesis of a new and highly energetic indandione based D-π-A planar molecule, 2-(5″-hexyl-[2,2′:5′2″ terthiophen]-5-yl) methylene)-1H- indene-1,3(2H) dione, H3T-ID), as donor material for bulk-heterojunction organic solar cells (BJH-OSCs). The photophysical properties, optoelectrical characterization and microscopic images were thoroughly studied. H3T-ID exhibited good absorption behavior with maximum absorbance at ~495 nm and displayed the optical band gap of ~1.98 eV. The existence of π-spacer and hexyl side chain in H3T-ID significantly improved the thin film morphology, molecular packing and enhanced the charge transport. H3T-ID organic molecule acquired well-matched HOMO and bountifully higher LUMO energy levels w.r.t. PC61BM acceptor. The photovoltaic characteristics of the fabricated BHJ-OSC using H3T-ID as donor and PC61BM as acceptor displayed maximum PCE = ~4.05%, good JSC = ~10.43 mAcm?2, VOC = ~0.77 V and FF = 0.51. The stability test revealed that the fabricated BHJ-OSCs showed good reproducibility and stability by retaining over ~80% of its initial PCE for 15 days without encapsulation.
关键词： Stability,Indanedione,Planar,Heterojunction,Organic solar cell
更新于2025-09-23 15:19:57
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Large signal analysis of multiple quantum well transistor laser: Investigation of imbalanced carrier and photon density distribution
摘要： In this paper, we present a large-signal and switching analysis for the Heterojunction Bipolar Transistor Laser (HBTL) to reveal its optical and electrical behavior under high current injection conditions. Utilizing appropriate models for carrier transport, nonlinear optical gain, and optical confinement factor, we have simulated the large-signal response of the HBTL in relatively low and high modulation frequencies. Our results predict that for multiple quantum well (MQW) structures at low frequencies, there should not be a difference in either the carrier density or the photon density. However, the carrier concentration can be differently distributed between subsequent wells in the case of a high speed yet large-signal input. This leads to increased linewidth instead as it depends on ΔNqw. We show the effect of different structural parameters on the switching behavior by performing a switching analysis of the single quantum well and MQW structures using computationally efficient numerical methods. A set of coupled rate equations are solved to investigate the large-signal and switching behavior of MQW-HBTL. Finally, to have a comprehensive judgment about this optoelectronic device, we introduce a relative performance factor taking into account all the optoelectronic characteristics such as the output power, ac current gain, modulation bandwidth, and base threshold current, as well as turn-on time in order to design a suitable TL for optoelectronic integrated circuits.
关键词： multiple quantum well,switching analysis,carrier density,Heterojunction Bipolar Transistor Laser,large-signal analysis,photon density
更新于2025-09-23 15:19:57
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Design of hole-transport-material free CH3NH3PbI3/CsSnI3 all-perovskite heterojunction efficient solar cells by device simulation
摘要： The hole-transport-material (HTM) free perovskite solar cells (PSCs) have drawn great attentions due to the simple structure, low fabrication cost and long term stability. However, the photoelectric conversion efficiency (PCE) of the HTM-free PCSs are still low comparing with the traditional sandwich type PSCs. In this work, a new HTM-free PSC is proposed with CH3NH3PbI3/CsSnI3 all-perovskite heterojunction as light-harvester and carbon as back electrode through simulation using the wxAMPS tools. The results are analyzed and compared with the traditional HTM-free perovskite solar cells. It reveals that the narrow band gap CsSnI3 broadens the absorption spectrum to near-infrared region and the high hole mobility favors efficient hole transfer. The optimal performance is achieved as Voc = 1.08 eV, Jsc = 25.33 mA/cm2, FF = 79.27%, PCE = 21.64%. Comparing to the bare CH3NH3PbI3 absorbing layer, the device efficiency of CH3NH3PbI3/CsSnI3 heterojunction is improved from 18.29% to 21.64%. This indicates that the proposed HTM-free PSC is promising for future photovoltaic and optoelectronics applications.
关键词： HTM-free,All-perovskite,Simulation,CH3NH3PbI3/CsSnI3 heterojunction
更新于2025-09-23 15:19:57
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Numerical simulation for optimization of an ultra-thin n-type WS2/p-type c-Si heterojunction solar cells
摘要： Recently, ultra-thin tungsten disul?de (WS2) has become one of the hot spots in the research of solar cell materials due to its excellent optical and electrical properties. In this study, we use AFORS-HET software version 2.5 at air mass 1.5 to simulate the structure of n-type WS2/p-type c-Si heterojunction solar cells. Our goal is to ?nd an appropriate way to improve the performance of n-type WS2/p-type c-Si heterojunction solar cells by simulation. Through optimizing the parameters of both WS2 layer and Si layer, we obtain a maximum photovoltaic conversion e?ciency of 20.57%. Subsequently, we investigate the in?uence of the ITO work function and the interface states on the performance of n-type WS2/p-type c-Si heterojunction solar cells. It’s found that through selecting the suitable ITO work function and decreasing the interface defect density, solar cell’s performance can be further improved. Our result indicates that ultra-thin WS2 is a promising photovoltaic material for the application in solar cells.
关键词： Work function,Heterojunction solar cells,Numerical simulation,Tungsten disul?de,Interface states
更新于2025-09-23 15:19:57
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Impact of Polymer Backbone Fluorination on the Charge Generation/Recombination Patterns and Vertical Phase Segregation in Bulk Heterojunction Organic Solar Cells
摘要： Incorporating fluorine (–F) substituents along the main-chains of polymer donors and acceptors is an effective strategy toward efficient bulk-heterojunction (BHJ) solar cells. Specifically, F-substituted polymers often exhibit planar conformations, leading to favorable packing, and electronic coupling. However, the effects of fluorine substituents on the charge generation and recombination characteristics that determine the overall efficiency of BHJ active layers remain critically important issues to examine. In this report, two PBDT[2X]T polymer analogs –poly[4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-thiophene] [PBDT[2H]T] and its F-substituted counterpart poly[4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-difluoro-thiophene] [PBDT[2F]T]—are studied to systematically examine how –F substituents impact the blend morphology, charge generation, carrier recombination and extraction in BHJ solar cells. Considering the large efficiency differences between PBDT[2H]T- and PBDT[2F]T-based BHJ devices, significant emphasis is given to characterizing the out-of-plane morphology of the blend films as vertical phase-separation characteristics are known to have dramatic effects on charge transport and carrier extraction in polymer-fullerene BHJ solar cells. Herein, we use electron energy loss spectroscopy (EELS) in tandem with charge transport characterization to examine PBDT[2X]T-fullerene blend films. Our analyses show that PBDT[2H]T and PBDT[2F]T possess very different charge generation, recombination and extraction characteristics, resulting from distinct aggregation, and phase-distribution within the BHJ blend films.
关键词： vertical phase segregation,bulk heterojunction,polymer backbone fluorination,organic solar cells,charge generation and recombination
更新于2025-09-23 15:19:57
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Near-direct bandgap WSe <sub/>2</sub> /ReS <sub/>2</sub> type-II pn heterojunction for enhanced ultrafast photodetection and high-performance photovoltaics
摘要： PN heterojunctions comprising layered van der Waals (vdW) semiconductors have been used to demonstrate current-rectifiers, photodetectors, and photovoltaic devices. However, a direct or near-direct heterointerface bandgap for enhanced photogeneration in high light-absorbing few-layer vdW materials remains unexplored. In this work, for the first time, density functional theory calculations show that the heterointerface of few-layer group-6 transition metal dichalcogenide (TMD) WSe2 with group-7 ReS2 results in a sizeable (0.7 eV) near-direct type-II bandgap. The interlayer IR bandgap is confirmed through IR photodetection and micro-photoluminescence measurements demonstrate type-II alignment. Few-layer flakes exhibit ultrafast response time (5 μs) and high responsivity (3 A/W) and large photocurrent-generation and responsivity-enhancement at the hetero-overlap region (10-100×). Large open-circuit voltage of 0.64 V and short-circuit current of 2.6 μA enable high output electrical power. Finally, long term air-stability and facile single contact metal fabrication process make the multi-functional few-layer WSe2/ReS2 heterostructure diode technologically promising for next-generation optoelectronics.
关键词： van der Waals heterostructure,pn heterojunction,ultrafast photodetection,near-direct bandgap,infrared photodetection,interlayer bandgap
更新于2025-09-23 15:19:57
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Novel boron doped p-type Cu2O thin film as hole selective contact in c-Si solar cell
摘要： P-type Cu2O thin film doped with trivalent cation Boron is demonstrated for the first time as an efficient hole selective layer for c-Si heterojunction solar cell. Cu2O and Cu2O:B films were deposited by rf- magnetron sputtering and the optical and electrical properties of the doped and undoped films were investigated. Boron doping enhanced the carrier concentration and the electrical conductivity of the Cu2O film. The band alignment of the Cu2O:B/Si heterojunction was investigated using XPS and UPS measurements. The Cu2O:B/Si interface has a valance band offset of 0.08 eV which facilitates hole transport and a conduction band offset of 1.35 eV which block the electrons. A thin SiOx tunnel oxide interlayer was also explored as the passivation layer. The initial trials of incorporating this Cu2O:B layer as hole transporting layer in a single heterojunction solar cell with the structure, ITO/Cu2O:B/n-Si/Ag, and cell area of 1 cm2 yielded an open-circuit voltage of 370 mV, short-circuit current density of 36.5 mA/cm2 and an efficiency of 5.4 %. This p-type material could find potential applications in various optoelectronic applications like organic solar cells, TFTs, and LEDs.
关键词： Silicon heterojunction,Photovoltaics,Carrier selective solar cells,Sputtering,Copper Oxide,Hole Selective layer
更新于2025-09-23 15:19:57
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Toward efficient polymer solar cells with thick bulk heterojunction by introducing iridium complex as an aggregation reshaping auxiliary
摘要： The morphology control of thick bulk heterojunction (BHJ) polymer solar cells (PSCs) is an important factor to determine their power conversion efficiency (PCE). Particularly, during the building of phase separation, aggregation morphology plays a prominent role in the control of both horizonal and vertical gradient distribution of donor/acceptor (D/A) in thick BHJ. In this work, we introduced a novel iridium complex of (tfmppy)2Ir(tpip) into the active layer of PffBT4T-2OD: PC71BM as an “aggregation reshaping auxiliary” to form a long and narrow aggregation shape in both horizontal and vertical directions. Through characterizing the morphology of active layer in details, it was found that the combination of 5% (tfmppy)2Ir(tpip) assists PffBT4T-2OD aggregation shape with a 1: 2.5 aspect ratio while maintaining high crystallinity. In addition, the results showed that the (tfmppy)2Ir(tpip) facilitates efficient exciton dissociation and charge transport because of increased contacting area of D/A interface. As a result, the short circuit current (JSC) and fill factor (FF) performances were both improved contemporaneously, leading to a 20.3% enhancement in PCE.
关键词： Charge transport,Polymer solar cells,Thick bulk heterojunction,Aggregation reshaping auxiliary,Iridium complex
更新于2025-09-23 15:19:57