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Forming a metal-free oxidatively-coupled agent, bicarbazole, as a defect passivation for HTM and an interfacial layer in a p-i-n perovskite solar cell exhibits nearly 20% efficiency
摘要： In this study we synthesized three simple and inexpensive (34–120 USD/g) 3,3′-bicarbazole–based hole transporting materials (BC-HTMs; NP-BC, NBP-BC and PNP-BC) through a metal-free oxidative coupling, in excellent yields (≥ 95%). These bicarbazoles contain phenylene or biphenylene substituents on the carbazole N atom, with extended π-conjugation achieved through phenylene units at the 6,6′-positions of the bicarbazole. When using NBP-BC as a dopant-free HTM in a p–i–n perovskite solar cell (PSC), we achieved a power conversion efficiency (PCE) of 13.04% under AM 1.5G conditions (100 mW cm–2); this PCE was comparable with that obtained when using PEDOT:PSS as the HTM (12.67%). BC-HTMs showed the large grain size (μm) of perovskite than PEDOT:PSS-based, due to defect passiviation on indium tin oxide (ITO) substrate and good hydrophobicity. Furthermore, we realized highly efficient and stable PSCs when using the p–i–n device structure ITO/NiOx/NP-BC/perovskite/PC61BM/BCP/Ag. The bifacial defect passivation effect of the interfacial layer improved the grain size of the perovskite layer and also enhanced the performance; the best performance of the NiOx/NP-BC device was characterized by a short-circuit current density (Jsc) of 22.38 mA cm–2, an open-circuit voltage (Voc) of 1.09 V, and a fill factor (FF) of 79.9%, corresponding to an overall PCE of almost 20%. This device structure has competitive potential because its performance is comparable with that of the record high efficiency PSCs. Under an Ar atmosphere, the PCE of the NiOx/NP-BC PSC device decayed by only 4.55% after 168 h; it retained 90.80% of its original PCE after 1000 h. A morphological study revealed that the films of the BC-HTMs were indeed smooth and hydrophobic, and that the perovskite films spin-coated upon them were uniform and featured large grains (micrometer scale). Time-resolved photoluminescence (TRPL) spectra of the perovskite films suggested that the hole extraction capabilities of the NiOx/BC-HTMs were better than that of the bare NiOx. The superior film morphologies of the NiOx/BC-HTMs were responsible for the performances of their devices being comparable with those of bare NiOx-based PSCs.
关键词： power conversion efficiency,3,3′-bicarbazole,perovskite solar cells,hole transporting materials,metal-free oxidative coupling,dopant-free
更新于2025-09-16 10:30:52
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Solvent Engineering of a Dopant-Free Spiro-OMeTAD Hole-Transport Layer for cm-Scale Perovskite Solar Cells having High Efficiency and Thermal Stability
摘要： High efficiency and environmental stability are mandatory performance requirements for commercialization of perovskite solar cells (PSCs). Herein, efficient cm-scale PSCs with improved stability were achieved by incorporating an additive-free 2,2’,7,7’-tetrakis[N,N-di(p-methoxyphenyl)amino]-9,9’-spirobifluorene (spiro-OMeTAD) hole transporting material (HTM) through simply substituting the usual chlorobenzene solvent with pentachloroethane (PC). A stabilized power conversion efficiency of 16.1% under simulated AM 1.5G 1-sun illumination with an aperture of 1.00 cm2 was achieved for PSCs using an additive-free spiro-OMeTAD layer cast from PC. X-ray analysis suggested chlorine radicals from pentachloroethane transferred partially to spiro-OMeTAD and retain in the HTM film, resulting of conductivity improvement. Moreover, unencapsulated PSCs having cm-scale active area cast from PC retained >70% of their initial PCE after ageing at 80 °C for 500 h, in contrast with less than 20% retention for control devices. Morphological and X-ray analysis of the aged cells revealed that the perovskite and HTM layers remain almost unchanged in the cells with spiro-OMeTAD layer cast from PC whereas serious degradation occurred in the control cells. This study not only reveals the decomposition mechanism of PSCs in the presence of HTM-additives, but also opens up a broad range of organic semiconductors for radical doping.
关键词： stability,spiro-OMeTAD,perovskite solar cell,hole transporting materials,dopant-free,radical,pentachloroethane
更新于2025-09-16 10:30:52
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Colloidal Seconda??Neara??infrareda??emitting Mna??doped Ag2S Quantum Dots
摘要： Incorporation of transition metal dopants within a semiconductor nanocrystal has a tremendous effect on the optical and magnetic properties of the semiconductor nanocrystals. Herein, we showed the novel synthesis of second-near-infrared-emitting photoluminescent Mn2+-doped Ag2S quantum dots via co-pyrolysis of silver and manganese single source precursors. The Mn2+ doping level was flexibly tuned in Ag2S quantum dots, which was confirmed by elemental analysis and electron paramagnetic resonance spectroscopy. The Mn2+ doping induced negligible change in the pristine monoclinic acanthite Ag2S crystal structure but significantly decreased the photoluminescent intensity. Mn2+ doped Ag2S QDs exhibit the second-near-infrared-emission and ferromagnetic ordering, which show potential applicability for multimodal fluorescence/MRI probes.
关键词： Second Near-infrared,Manganese Dopant,Ferromagnetism,Quantum Dot,Silver Sulfide
更新于2025-09-16 10:30:52
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Influence of post deposition fabrication steps and quantitative estimation of band diagram of Si/MoOX heterojunction for carrier selective solar cells
摘要： Heterojunction of molybdenum oxide with silicon is used as an effective hole collector in Si based carrier selective solar cells. Although the deposition of MoOX on Si is a low temperature process, the subsequent processes involved in the fabrication of the solar cell can impact the hole collection efficiency of Si/MoOX junction. In this manuscript we address the influence of post-deposition fabrication processes the subsequent processes involved in the fabrication of the solar cell can impact the hole collection efficiency of Si/MoOX junction. In this work we have found that the necessary annealing and sputtering steps have a degrading impact on the heterojunction. The underlying reasons are identified and widely described. Furthermore, to gain insight into the unique transport mechanism of heterojunction, a quantitative band diagram is obtained based on the empirical data (electron spectroscopy, optical and electrical measurements). The workfunction of thermally evaporated MoOX is found to be strongly substrate dependent and the electron affinity is deduced and measured to be 5.09 eV. The doping of MoOX films due to oxygen vacancies is found to be non-uniform as the oxygen content of the film decreases rapidly, from MoOX surface to Si/MoOX interface. Lastly, we report Si/MoOX heterojunction solar cells with high short circuit current of 33.9 mA/cm2, an open circuit voltage (VOC) of 585 mV, and an efficiency of 12.8%.
关键词： Heterojunction,Dopant-free solar cells,Molybdenum oxide
更新于2025-09-12 10:27:22
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Dopant-free molecular hole transport material that mediates a 20% power conversion efficiency in a perovskite solar cell
摘要： Organic molecular hole-transport materials (HTMs) are appealing for the scalable manufacture of perovskite solar cells (PSCs) because they are easier to reproducibly prepare in high purity than polymeric and inorganic HTMs. There is also a need to construct PSCs without dopants and additives to avoid formidable engineering and stability issues. We report here a power conversion efficiency (PCE) of 20.6% with a molecular HTM in an inverted (p–i–n) PSC without any dopants or interlayers. This new benchmark was made possible by the discovery that, upon annealing, a spiro-based dopant-free HTM (denoted DFH) containing redox-active triphenyl amine (TPA) units undergoes preferential molecular organization normal to the substrate. This structural order, governed by the strong intermolecular interactions of the DFH dioxane groups, affords high intrinsic hole mobility (1 (cid:2) 10(cid:3)3 cm2 V(cid:3)1 s(cid:3)1). Annealing films of DFH also enables the growth of large perovskite grains (up to 2 lm) that minimize charge recombination in the PSC. DFH can also be isolated at a fraction of the cost of any other organic HTM.
关键词： molecular organization,dopant-free,perovskite solar cells,hole-transport materials,power conversion efficiency
更新于2025-09-12 10:27:22
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Fluorination of pyrene-based organic semiconductors enhances the performance of light emitting diodes and halide perovskite solar cells
摘要： In this work, a fluorinated pyrene-based organic semiconductor (L-F) has been designed and synthesized starting from a low-cost pyrene core functionalized with triphenilamine substituents at 1,3,6,8 positions (L-H), obtained via Suzuki coupling reactions. Its performance when used as green emitter in organic light emitting diodes (OLEDs) or as dopant-free hole-transporting material (HTM) in halide perovskite solar cells (PSCs) is higher than the L-H counterpart, in spite of its lower bulk hole-mobility (7.0 x 10-6 cm2/Vs) with respect to L-H (1.9 x 10-4 cm2/Vs). In fact, the OLED devices based on L-F active layer showed excellent green emission (brightness and current efficiency were1759.8 cd/m2 and 3.7 cd/A, respectively) at a 4.5 V turn-on voltage. When the molecules were employed as a dopant-free HTM in PSCs, L-F led to a power conversion efficiency (PCE) and open circuit voltage (Voc) of 5.9 % and 1.07 V, respectively, thus outperforming those of corresponding devices based on L-H (PCE = 5.0% and Voc = 0.87 V) under similar experimental conditions (AM 1.5G and 100 mW cm2). We attribute the enhancements of L-F-based optoelectronic devices (OLEDs and PSCs) to the observed better quality of theL-F films. The promising performance of L-F indicates that fluorination of small molecules can be an effective strategy to achieve low-cost and high-performing materials for energy harvesting and display-based organic electronic devices.
关键词： pyrene,perovskite solar cells,hole transporting material,triphenylamine,fluorination,dopant-free,organic light emitting diodes
更新于2025-09-12 10:27:22
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Lead Oxalate-Induced Nucleation Retardation for High-Performance Indoor and Outdoor Perovskite Photovoltaics
摘要： Perovskite solar cells have attracted worldwide attention as one of the key research areas in the field of thin film photovoltaics. Although, they exhibit easy solution-processability, it is important to effectively control the crystallization of the light absorbing layer which affects the performance and stability of devices. Here, we present lead oxalate (PbC2O4) as a non-halide lead constituent of the perovskite precursor solution, which contributes to anion replacement during thin film annealing. This strategy limits the perovskite nucleation rate and retards crystallization. As a result, we achieved excellent perovskite film with larger grains and less defects. The open circuit voltage of the optimal device under one sun illumination rose to 1.12 V with a power conversion efficiency (PCE) of 20.20%. In addition, the indoor PCE at 1000 lux can reach 34.86%. This non-halide lead compound dopant provides a guide on the crystallization of perovskite materials and paves a way for the fabrication of non-halide perovskite solar cells.
关键词： PbC2O4,Perovskite solar cells,Nucleation retardation,Non-halide lead dopant
更新于2025-09-12 10:27:22
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Hard mask processing of 20% efficiency back-contacted silicon solar cells with dopant-free heterojunctions
摘要： Single junction crystalline silicon (c-Si) solar cells featuring a conventionally doped interdigitated back contact heterojunction (IBC-SHJ) structure has approached a record efficiency of 26.6%, which is very close to the practical limit. However, integrating the interdigital p- and n-type amorphous silicon (a-Si:H) layers on the rear surface of Si substrate is of such complexity, posing problem of heavy dependences on expensive manufacturing techniques including plasma-enhanced chemical vapor deposition and photolithography. Its commercial potential is thus always being questioned, and to seek an alternative fabrication procedure, which adapts to cost-effective deposition parallel with simple patterning characteristics, has been a primary research target of related subjects. Here, we demonstrated 20.1% efficiency dopant-free IBC-SHJ solar cells by combining evaporated carrier-selective materials (MoOx and LiFx) and two-steps hard masks alignments, delivering substantial simplifications in the architecture and fabrication procedures. We investigated the effect of intrinsic a-Si:H films with different thicknesses on the passivation and contact resistance for both a-Si:H/MoOx and a-Si:H/LiFx contacts, showing 4 nm a-Si:H is better for high efficiency IBC-SHJ solar cells. We also found that the position of the metal target (electrode definition step) and isolation in between the busbar and the Si substrate are highly relevant to leakage and recombination and have great impact on the device performance. The dopant-free IBC-SHJ solar cells demonstrated here manifest enough confidence in our hard mask based fabrication procedure, with great potential for high performance-to-cost ratio in future.
关键词： solar cells,dopant-free,interdigitated back contact,silicon,carrier-selective,contacts,heterojunction
更新于2025-09-12 10:27:22
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Electro-active nanofibers of a tetrathiafulvalene derivative with amide hydrogen bonds as a dopant-free hole transport material for perovskite solar cells
摘要： A tetrathiafulvalene derivative containing two amide units for intermolecular hydrogen bonds (Bis-amide-TTF) was found to form supramolecular assemblies, in which intermolecular TTF cores were stacked with each other. The electrical conductivity of Bis-amide-TTF-based film was 1.28 × 10?5 S cm?1, which was greater than that of spiro-OMeTAD doped with lithium salt and t-butylpyridine (8.37 × 10?6 S cm?1). Bis-amide-TTF was applied as a hole transport material (HTM) for perovskite solar cells (PSCs). The Bis-amide-TTF film has a deeper HOMO level than that of spiro-OMeTAD, leading to an increased open-circuit voltage of the PSCs. The power conversion efficiency of 14.5% with a short-circuit current density (Jsc) of 19.8 mA cm?2, an open-circuit voltage (Voc) of 1.11 V, and a fill factor (FF) of 66% was achieved for PSCs fabricated with the dopant-free Bis-amide-TTF-based HTM, which was comparable to that obtained with spiro-OMeTAD with the dopants (15.5%).
关键词： Hole transport materials,Nanofibers,Hydrogen bonds,Tetrathiafulvalene,Dopant free,Perovskite solar cells
更新于2025-09-12 10:27:22
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Investigation of p+ emitter formation for n-type silicon solar cells application
摘要： Investigation of p+ emitter formation for n-type silicon solar cells application. This work reports on the study of boron diffusion in n-type silicon from preform source for p+ emitter formation. Using quartz tube furnace, three main parameters are investigated that are: drive-in temperature, drive-in time and temperature ramp-up time. It is found that the sheet resistance as measured by the four point probe method (4-pp) decreases from 93 Ω/□ to 24 Ω/□ as the drive-in temperature increases from 850°C to 950°C, likewise, it decreases from 57 Ω/□ to 38 Ω/□ as the drive-in time increases from 20 min to 40 min. The electrically active boron dopant profiles as measured by the electrochemical capacitance voltage technique (ECV) exhibit surface concentrations below the solid-solubility limit of boron in silicon for all the studied emitters, the maximum surface and peak boron concentrations of 1.30x1020 and 1.58x1020 atoms/cm3 were measured respectively on the emitter which is formed at a drive-in temperature of 950°C. Furthermore, it is revealed from the secondary ion mass spectroscopy measurements (SIMS) the presence of the boron rich layer (BRL) on its surface. The Hall Effect measurement method is used for measuring sheet resistance and sheet charge carrier concentration.
关键词： N-type silicon,Boron dopant profile,Solar cells,Preform source,Boron diffusion
更新于2025-09-12 10:27:22