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Herein, we synthesized two donor-acceptor (D-A) type small organic molecules with self-assembly properties, namely MPA-BT-BA and MPA-2FBT-BA, both containing a low acidity anchoring group, benzoic acid. After systematically investigation, it is found that, with the fluorination, the MPA-2FBT-BA demonstrates a lower highest occupied molecular orbital (HOMO) energy level, higher hole mobility, higher hydrophobicity and stronger interaction with the perovskite layer than that of MPA-BT-BA. As a result, the device based-on MPA-2FBT-BA displays a better crystallization and morphology of perovskite layer with larger grain size and less non-radiative recombination. Consequently, the device using MPA-2FBT-BA as hole transport material achieved the power conversion efficiency (PCE) of 20.32 % and remarkable stability. After being kept in an N2 glove box for 116â days, the unsealed PSCs' device retained 93 % of its initial PCE. Even exposed to air with a relative humidity range of 30±5 % for 43â days, its PCE remained above 91 % of its initial condition. This study highlights the vital importance of the fluorination strategy combined with a low acidity anchoring group in SAMs, offering a pathway to achieve efficient and stable PSCs.
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All inorganic perovskite based on CsPbI2 Br has attracted significant attention due to its relatively thermal stable structure compare to its hybrid counterparts. With a wide bandgap of 1.9 eV and excellent light absorption capability, it has been extensively explored for applications in indoor photovoltaics and as a front absorber in tandem devices. However, the uncontrollable crystallization process during solvent evaporation and thermal annealing leads to both macroscopic defects like cracks and microscopic defects such as voids. In this study, a metastable adduct with lead (II) halides by incorporating 4-tert-butyl pyridine as a volatile Lewis base monodentate ligand in the precursor solution is formed. The strategic preferential decomposition of the adduct during the early-stage low-temperature annealing facilitated the desorption of lead (II) halides, inducing antisolvent-free heterogenous nucleation. This, in turn, promoted crystal growth during subsequent high-temperature annealing, resulting in dense films with low defect density. As a result, a maximum open-circuit voltage of 1.30 V is achieved with the champion power conversion efficiency of 16.5% in CsPbI2 Br-based perovskite solar cell. The work reveals a new mechanism of using Lewis acid-base adduct to obtain high quality perovskite films other than hindering crystallization in traditional way.
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Two-dimensional (2D) hybrid perovskites with novel functionalities and structural diversity are a perfect platform for emerging optoelectronic devices such as photodetectors, light-emitting diodes, and solar cells. Here, we demonstrate that excess concentration of Cesium bromide (CsBr) is key to the formation of easily exfoliated 2D Cs2 Cu(Cl/Br)4 perovskite crystal. Furthermore, by employing this trick to 2D perovskite MA2 Cu(Cl/Br)4 (MA=methylammonium), we achieve a phase-pure easily exfoliated 2D mixed-cation (MA/Cs)2 Cu(Cl/Br)4 perovskite crystal, which exhibits reduced bandgap (1.53â eV) with ferromagnetic behavior and photovoltaic property. The resultant mixed-cation structured device reveals enhanced efficiency compared to all MA and all Cs counterparts. These findings demonstrate the importance of cation-engineering in developing innovative materials with novel properties.
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A new hole transporting material (HTM) named DMZ is synthesized and employed as a dopant-free HTM in inverted planar perovskite solar cells (PSCs). Systematic studies demonstrate that the thickness of the hole transporting layer can effectively enhance the morphology and crystallinity of the perovskite layer, leading to low series resistance and less defects in the crystal. As a result, the champion power conversion efficiency (PCE) of 18.61% with JSC = 22.62 mA cm-2 , VOC = 1.02 V, and FF = 81.05% (an average one is 17.62%) is achieved with a thickness of ≈13 nm of DMZ (2 mg mL-1 ) under standard global AM 1.5 illumination, which is ≈1.5 times higher than that of devices based on poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT:PSS). More importantly, the devices based on DMZ exhibit a much better stability (90% of maximum PCE retained after more than 556 h in air (relative humidity ≈ 45%-50%) without any encapsulation) than that of devices based on PEDOT:PSS (only 36% of initial PCE retained after 77 h in same conditions). Therefore, the cost-effective and facile material named DMZ offers an appealing alternative to PEDOT:PSS or polytriarylamine for highly efficient and stable inverted planar PSCs.
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Solution processable semiconducting polymers with excellent film forming capacity and mechanical flexibility are considered among the most progressive alternatives to conventional inorganic semiconductors. However, the random packing of polymer chains and the disorder of the polymer matrix typically result in low charge transport mobilities (10(-5)-10(-2) cm(2) V(-1) s(-1)). These low mobilities compromise their performance and development. Here, we present a strategy, by utilizing capillary action, to mediate polymer chain self-assembly and unidirectional alignment on nanogrooved substrates. We designed a sandwich tunnel system separated by functionalized glass spacers to induce capillary action for controlling the polymer nanostructure, crystallinity, and charge transport. Using capillary action, we demonstrate saturation mobilities with average values of 21.3 and 18.5 cm(2) V(-1 )s(-1) on two different semiconducting polymers at a transistor channel length of 80 µm. These values are limited by the source-drain contact resistance, Rc. Using a longer channel length of 140 µm where the contact resistance is less important, we measured µh = 36.3 cm(2) v(-1) s(-1). Extrapolating to infinite channel length where Rc is unimportant, the intrinsic mobility for poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]thiadiazolo[3,4-c]pyridine] (Mn = 140 kDa) at this degree of chain alignment and structural order is µh ≈ 47 cm(2 )v(-1) s(-1). Our results create a promising pathway toward high performance, solution processable, and low-cost organic electronics.
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Microstructured porous zinc oxide (ZnO) thin film was developed and demonstrated as an electron selective layer for enhancing light scattering and efficiency in inverted organic photovoltaics. High degree of porosity was induced and controlled in the ZnO layer by incorporation of polyethylene glycol (PEG) organic template. Scanning electron microscopy, contact angle and absorption measurements prove that the ZnO:PEG ratio of 4:1 is optimal for the best performance of porous ZnO. Ensuring sufficient pore-filling, the use of porous ZnO leads to a marked improvement in device performance compared to non-porous ZnO, with 35% increase in current density and 30% increase in efficiency. Haze factor studies indicate that the performance improvement can be primarily attributed to the improved light scattering enabled by such a highly porous structure.
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Fontes de Energia Elétrica , Nanoestruturas/química , Polietilenoglicóis/química , Refratometria/instrumentação , Óxido de Zinco/química , Desenho de Equipamento , Análise de Falha de Equipamento , Luz , Nanoporos/ultraestrutura , Nanoestruturas/efeitos da radiação , Nanoestruturas/ultraestrutura , Espalhamento de Radiação , Semicondutores , Energia Solar , Óxido de Zinco/efeitos da radiaçãoRESUMO
We demonstrate that the power conversion efficiency can be significantly improved in solution-processed small-molecule solar cells by tuning the thickness of the active layer and inserting an optical spacer (ZnO) between the active layer and the Al electrode. The enhancement in light absorption in the cell was measured with UV-vis absorption spectroscopy and by measurements of the photoinduced carriers generation rate. The ZnO layer used to improve the light-harvesting increases the charge collection efficiency, serves as a blocking layer for holes, and reduces the recombination rate. The combined optical and electrical improvements raise the power conversion efficiency of solution-processed small-molecule solar cells to 8.9%, that is, comparable to that of polymer counterparts.
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Perovskite based on cesium bismuth bromide offers a compelling, non-toxic alternative to lead-containing counterparts in optoelectronic applications. However, its widespread usage is hindered by its wide bandgap. This study investigates a significant bandgap tunability achieved by introducing Fe doping into the inorganic, lead-free, non-toxic, and stable Cs3Bi2Br9 perovskite at varying concentrations. The materials were synthesized using a facile method, with the aim of tuning the optoelectronic properties of the perovskite materials. Characterization through techniques such as X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, energy dispersive spectroscopy (EDS), and UV-vis spectroscopy was conducted to elucidate the transformation mechanism of the doping materials. The substitution process results in a significant change in the bandgap energy, transforming from the pristine Cs3Bi2Br9 with a bandgap of 2.54 eV to 1.78 eV upon 70% Fe doping. The addition of 50% Fe in Cs3Bi2Br9 leads to the formation of the orthorhombic structure in Cs2(Bi,Fe)Br5 perovskite, while complete Fe alloying at 100% results in the phase formation of CsFeBr4 perovskite. Our findings on regulation of bandgap energy and crystal structure through B site substitution hold significant promise for applications in optoelectronics.
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The application of carbon nanotube (CNT) yarns as thermoelectric materials for harvesting energy from low-grade waste heat including that generated by the human body, is attracting considerable attention. However, the lack of efficient n-type CNT yarns hinders their practical implementation in thermoelectric devices. This study reports efficient n-doping of CNT yarns, employing 4-(1, 3-dimethyl-2, 3-dihydro-1H-benzimidazole-2-yl) phenyl) dimethylamine (N-DMBI) in alternative to conventional n-dopants, with o-dichlorobenzene emerging as the optimal solvent. The small molecular size of N-DMBI enables highly efficient doping within a remarkably short duration (10 s) while ensuring prolonged stability in air and at high temperature (150 °C). Furthermore, Joule annealing of the yarns significantly improves the n-doping efficiency. Consequently, thermoelectric power factors (PFs) of 2800, 2390, and 1534 µW m-1 K-2 are achieved at 200, 150, and 30 °C, respectively. The intercalation of N-DMBI molecules significantly suppresses the thermal conductivity, resulting in the high figure of merit (ZT) of 1.69×10-2 at 100 °C. Additionally, a π-type thermoelectric module is successfully demonstrated incorporating both p- and n-doped CNT yarns. This study offers an efficient doping strategy for achieving CNT yarns with high thermoelectric performance, contributing to the realization of lightweight and mechanically flexible CNT-based thermoelectric devices.
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Metal halide perovskites, particularly the quasi-two-dimensional perovskite subclass, have exhibited considerable potential for next-generation electroluminescent materials for lighting and display. Nevertheless, the presence of defects within these perovskites has a substantial influence on the emission efficiency and durability of the devices. In this study, we revealed a synergistic passivation mechanism on perovskite films by using a dual-functional compound of potassium bromide. The dual functional potassium bromide on the one hand can passivate the defects of halide vacancies with bromine anions and, on the other hand, can screen the charged defects at the grain boundaries with potassium cations. This approach effectively reduces the probability of carriers quenching resulting from charged defects capture and consequently enhances the radiative recombination efficiency of perovskite thin films, leading to a significant enhancement of photoluminescence quantum yield to near-unity values (95%). Meanwhile, the potassium bromide treatment promoted the growth of homogeneous and smooth film, facilitating the charge carrier injection in the devices. Consequently, the perovskite light-emitting diodes based on this strategy achieve a maximum external quantum efficiency of ~ 21% and maximum luminance of ~ 60,000 cd m-2. This work provides a deeper insight into the passivation mechanism of ionic compound additives in perovskite with the solution method.
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To restrain the chemical reaction at cathode interface of organic solar cells, two cathode interfacial materials are synthesized by connecting phenanthroline with carbolong unit. Consequently, the D18:L8-BO based organic solar cell with double-phenanthroline-carbolong achieve the highest efficiency of 18.2%. Double-phenanthroline-carbolong with larger steric hindrance and stronger electron-withdrawing property confirms to suppress the interfacial reaction with norfullerene acceptor, resulting the most stable device. Double-phenanthroline-carbolong based device can sustain 80% of its initial efficiency for 2170 h in dark N2 atmosphere, 96 h under 85 oC and keep 68% initial efficiency after been illuminated for 2200 h, which are significantly better than bathocuproin based devices. Moreover, superb interfacial stability of double-phenanthroline-carbolong cathode interface enables thermal posttreatment of organic sub-cell in perovskite/organic tandem solar cells and obtained a remarkable efficiency of 21.7% with excellent thermal stability, which indicates the potentially wide application of phenanthroline-carbolong materials for stable and efficient solar device fabrications.
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Atmosfera , Fenantrolinas , Eletrodos , ElétronsRESUMO
In this study, we investigated the impact of benzophenone (BP), a small molecule additive, on the performance and stability of inverted perovskite solar cells (PSCs). Specifically, we introduced BP into the perovskite precursor solution of FAPbI3 to fabricate PSCs with an ITO/PEDOT:PSS/BP:FAPbI3/PCBM/C60/PCB/Ag architecture. The incorporation of BP with an optimum concentration of 2 mg mL-1 significantly enhanced the power conversion efficiency (PCE) of the inverted PSC from 13.12 to 18.84% with negligible hysteresis. Notably, the BP-based PSCs retained â¼90% of their initial PCE after being stored in ambient air with 30% relative humidity at 25 °C for 700 h. In contrast, control devices showed rapid degradation, retaining only 30% of their initial value within 300 h under the same conditions. We attributed the superior performance and stability of the BP-based PSCs to the grain boundary passivation of the perovskite film. The improvement was mainly attributed to the intermolecular interaction between the O-donor Lewis base BP material and both Pb2+ and FA+ in FAPbI3. This effectively suppresses trap-assisted recombination and promotes the conversion of the δ-phase to photoactive and stable α-phase FAPbI3. Overall, our findings suggest that BP is a promising additive for improving the performance and stability of inverted PSCs.
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Fine-tuning the alkyl chains and end groups of non-fused ring electron acceptors (NFREAs) plays vital roles in the promotion of charge transfer (CT) and power conversion efficiency (PCE). In this work, we developed a series of A-D-A'-D-A-type NFREAs, which possess the same terminals (A), the cyclopentadithiophene unit (D), and the thieno[3,4-c]pyrrole-4,6-dione (A'). Despite the subtle difference in side chains and halogenated end groups, the six acceptors exhibit a considerable difference in the efficiency and device stability of the organic solar cells (OSCs). Among the molecules, chlorinated NFREAs show a broader light absorption than the fluorinated ones do. Compared with C8C8-4F (1-octylnonyl and fluorination) and C6C4-4Cl (2-butyloctyl and chlorination), C8C8-4Cl (1-octylnonyl and chlorination) exhibits a lower highest occupied molecular orbital level, higher electron mobility, and denser molecular packing. The OSCs based on PM6:C8C8-4Cl yield the best PCE of 14.11%, which is attributed to the faster charge transport, high miscibility, and preferable morphology. Moreover, the PM6:C8C8-4Cl devices retain 91.1% of the initial PCE after being placed in air with 67% relative humidity for 50 days. This work shows that the simultaneous optimization of side chains and end groups facilitates the CT and improves the stability in the OSCs, offering a novel view into the molecular design of A-D-A'-D-A-type NFREAs.
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Organic solar cells (OSCs) based on polymer donor and non-fullerene acceptor achieve power conversion efficiency (PCE) more than 19% but their poor absorption below 550 nm restricts the harvesting of high-energy photons. In contrast, wide bandgap all-inorganic perovskites limit the absorption of low-energy photons and cause serious below bandgap loss. Therefore, a 2-terminal (2T) monolithic perovskite/organic tandem solar cell (TSC) incorporating wide bandgap CsPbI2 Br is demonstrated as front cell absorber and organic PM6:Y6 blend as rear cell absorber, to extend the absorption of OSCs into high-energy photon region. The perovskite sub-cell, featuring a sol-gel prepared ZnO/SnO2 bilayer electron transporting layer, renders a high open-circuit voltage (VOC ). The VOC is further enhanced by employing thermal annealing (TA)-free process in the fabrication of rear sub-cell, demonstrating a record high VOC of 2.116 V. The TA-free Ag/PFN-Br interface in organic sub-cell facilitates charge transport and restrains nonradiative recombination. Consequently, a remarkable PCE of 20.6% is achieved in monolithic 2T-TSCs configuration, which is higher than that of both reported single junction and tandem OSCs, demonstrating that tandem with wide bandgap all-inorganic perovskite is a promising strategy to improve the efficiency of OSCs.
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Blue-color-emitting organic semiconductors are of significance for organic light-emitting diodes (OLEDs). In this study, through Suzuki coupling polymerization, three 1,4-naphthalene-based copolymers-namely, PNP(1,4)-PT, PNP(1,4)-TF, and PNP(1,4)-ANT-were designed and synthesized. The variation of comonomers, phenothiazine (PT), triphenylamine substituted fluorene (TF), and anthanthrene (ANT), effectively tuned the emitting color and device performance of poly(9-vinyl carbazole) (PVK)-based OLEDs. Especially, the polymer PNP(1,4)-TF, bearing perpendicular aryl side groups, showed a most twisted structural geometry, which enabled an ultra-high thermal stability and a best performance with blue emitting in PVK-host-based OLEDs. Overall, in this work, we demonstrate a promising blue-color-emitting polymer through structural geometry manipulation.
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A new dopant-free hole transporting material (HTM) 4',4â´,4â´'',4â´''''-(adamantane-1,3,5,7-tetrayl)tetrakis(N,N-bis(4-methoxyphenyl)-[1,1'-biphenyl]-4-amine) (Ad-Ph-OMeTAD) (named FDY for short), which consists of a nonconjugated 3D bulky caged adamantane (Ad) as the core, triphenyl amines as side arms, and phenyl units as a linking bridge, is synthesized and applied in an inverted planar perovskite solar cell (PSC). As a result, the champion device with FDY as HTM yields an impressive power of conversion efficiency (PCE) of 18.69%, with JSC = 22.42 mA cm-2, VOC = 1.05 V, and FF = 79.31% under standard AM 1.5G illumination, which is ca. 20% higher than that of the device based on PEDOT:PSS (only 15.41%). Notably, the stability of PSC based on FDY is much better than that of devices based on PEDOT:PSS, and the corresponding devices retain over 90% of their initial PCEs after storing for 60 days in a nitrogen glove box without any encapsulation. Even when stored in an open air condition with 50-60% relative humidity for 188 h, the retained PCE is still over 81% of its initial one. All these results demonstrate that the new design strategy by combing the bulky and nonconjugated (aliphatic) adamantane unit as the core and triphenyl amines as side arms can efficiently develop highly efficient HTMs for PSCs, which is different from the traditional way based on conjugated backbones, and it may open a new way for scientists to design small-molecule HTMs for PSCs.
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Organic-inorganic halide perovskites have demonstrated significant light detection potential, with a performance comparable to that of commercially available photodetectors. In this study, a general design guideline, which is applicable to both inverted and regular structures, is proposed for high-performance perovskite photodiodes through an interfacial built-in electric field (E) for efficient carrier separation and transport. The interfacial E generated at the interface between the active and charge transport layers far from the incident light is critical for effective charge carrier collection. The interfacial E can be modulated by unintentional doping of the perovskite, whose doping type and density can be easily controlled by the post-annealing time and temperature. Employing the proposed design guideline, the inverted and regular perovskite photodiodes exhibit the external quantum efficiency of 83.51% and 76.5% and responsivities of 0.37 and 0.34 A W-1 , respectively. In the self-powered mode, the dark currents reach 7.95 × 10-11 and 1.47 × 10-8 A cm-2 , providing high detectivities of 7.34 × 1013 and 4.96 × 1012 Jones, for inverted and regular structures, respectively, and a long-term stability of at least 1600 h. This optimization strategy is compatible with existing materials and device structures and hence leads to substantial potential applications in perovskite-based optoelectronic devices.
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We report on the facile synthesis of a water-dispersible conducting polymer, polyazulene-polystyrenesulfonate (PAZ:PSS), using PSS as a template. PAZ:PSS can achieve an overall conductivity up to 0.1 S cm-1, and an ion Seebeck coefficient as high as 4500 µV K-1, demonstrating that PAZ:PSS is another promising water-dispersible polymer for thermoelectrics.
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An electron-rich fused indoloindole-based poly(indoloindole-selenophene vinylene selenophene) was synthesized and characterized. Soxhlet can be obtained by continuously purifying the product with a specific solvent and obtaining a pure polymer with a high concentration. Molecular weight is affected by the vapor pressure of marginal solvent, and the polymer was fractionated using tetrahydrofuran, chloroform, and chlorobenzene. Solubility is closely related to the morphology of bulk heterojunction and device parameters. In the solution process of fabricating the organic solar cell, securement of solubility has a great effect on the performance of the device, because morphology and orientation of a photo-active layer which significantly affect charge transport in the device. Since tetrahydrofuran (THF) Soxhlet solvents have high vapor pressure and appropriate solubility parameters, THF induced the best solubility of P-IDI-SVS materials for organic solvents. And through additive optimization, the performance of the device based on P-IDI-SVS from THF-Soxhlet extraction was enhanced. This is expected to be a meaningful study because the effect on solubility of Soxhlet solvent suggests factors to be considered in the solution process in organic solar cell research. In addition, surface modified bulk heterojunction was observed using atomic force microscopy, photoluminescence, time-correlated single photon counting and Raman spectroscopy analysis.
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Flexible, light-weight and robust thermoelectric (TE) materials have attracted much attention to convert waste heat from low-grade heat sources, such as human body, to electricity. Carbon nanotube (CNT) yarn is one of the potential TE materials owing to its narrow band-gap energy, high charge carrier mobility, and excellent mechanical property, which is conducive for flexible and wearable devices. Herein, we propose a way to improve the power factor of CNT yarns fabricated from few-walled carbon nanotubes (FWCNTs) by two-step method; Joule-annealing in the vacuum followed by doping with p-type dopants, 2,3,5,6-tetrafluo-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). Numerical calculations and experimental results explain that Joule-annealing and doping modulate the electronic states (Fermi energy level) of FWCNTs, resulting in extremely large thermoelectric power factor of 2250 µW m-1 K-2 at a measurement temperature of 423 K. Joule-annealing removes amorphous carbon on the surface of the CNT yarn, which facilitates doping in the subsequent step, and leads to higher Seebeck coefficient due to the transformation from (semi) metallic to semiconductor behavior. Doping also significantly increases the electrical conductivity due to the effective charge transfers between CNT yarn and F4TCNQ upon the removal of amorphous carbon after Joule-annealing.