Showing papers by "Alex K.-Y. Jen published in 2015"
TL;DR: An effective approach to significantly increase the electrical conductivity of a NiOx hole-transporting layer (HTL) to achieve high-efficiency planar heterojunction perovskite solar cells is demonstrated.
Abstract: An effective approach to significantly increase the electrical conductivity of a NiOx hole-transporting layer (HTL) to achieve high-efficiency planar heterojunction perovskite solar cells is demonstrated Perovskite solar cells based on using Cu-doped NiOx HTL show a remarkably improved power conversion efficiency up to 1540% due to the improved electrical conductivity and enhanced perovskite film quality General applicability of Cu-doped NiOx to larger bandgap perovskites is also demonstrated in this study
743 citations
TL;DR: In this article, the authors summarize the latest developments in solution-processed interfacial layers that have contributed to the significantly improved performance of polymer and perovskite solar cells (PSCs and PVSCs).
Abstract: In this review, we summarize the latest developments in solution-processed interfacial layers that have contributed to the significantly improved performance of polymer and perovskite solar cells (PSCs and PVSCs). The solution-processed interfacial materials, including organic electrolytes, organic–inorganic hybrids, graphene oxides (GOs), transition metal oxides (TMOs), and self-assembled functional materials, along with their integration into efficient PSCs, polymer tandem cells (PTCs), and the emerging perovskite solar cells (PVSCs) are discussed. Regarding the rapid progress of PSCs and PVSCs, strategies and perspectives of further improving solution-processed interfacial materials are also discussed to help readers understand the challenges and opportunities in transitioning from scientific curiosity into technology translation for realizing low-cost, printable, and high-efficiency flexible solar cells to address the scalability issues facing solar energy.
696 citations
TL;DR: Fluorinated n-type conjugated polymers are used as efficient electron acceptor to demonstrate high-performance all-polymer solar cells to result in enhanced photocurrent and suppressed charge recombination.
Abstract: Fluorinated n-type conjugated polymers are used as efficient electron acceptor to demonstrate high-performance all-polymer solar cells. The exciton generation, dissociation, and charge-transporting properties of blend films are improved by using these fluorinated n-type polymers to result in enhanced photocurrent and suppressed charge recombination.
411 citations
TL;DR: Low-temperature, solution-processable Cu-doped NiOX (Cu:NiOx ), prepared via combustion chemistry, is demonstrated as an excellent hole-transporting layer (HTL) for thin-film perovskite solar cells (PVSCs).
Abstract: Low-temperature, solution-processable Cu-doped NiOX (Cu:NiOx ), prepared via combustion chemistry, is demonstrated as an excellent hole-transporting layer (HTL) for thin-film perovskite solar cells (PVSCs). Its good crystallinity, conductivity, and hole-extraction properties enable the derived PVSC to have a high power conversion efficiency (PCE) of 17.74%. Its general applicability for various elecrode materials is also revealed.
388 citations
TL;DR: In this article, a spin and blade-coating process was applied to the preparation of CH 3 NH 3 PbI 3x Cl x perovskite cells to achieve high quality and moisture/air-resistant properties under ambient conditions.
Abstract: DOI: 10.1002/aenm.201401229 that the blade-coating process encourages the formation of self-assembled large perovskite crystalline domains featuring uniform fi lm coverage and signifi cantly improved device ambient stability. In addition, we reveal that this blade-coating process can also be applicable to systems based on using the advanced solvent engineering technique reported for high-performance perovskite (CH 3 NH 3 PbI 3 ) solar cells. [ 35,36 ] Blade-coating is a simple, cost-effi cient, and roll-to-roll compatible process for optoelectronic device fabrication. [ 37,38 ] In the case of perovskites, we fi nd that the formation of large crystalline domains is encouraged by the relatively slow solvent drying process in the uniformly wet fi lm formed immediately after solution blading. It may change the nucleation kinetics of perovskites to ensure self-assembly driven growth. Taking advantage of this process, we have applied blade-coating to the preparation of CH 3 NH 3 PbI 3x Cl x perovskite fi lms to achieve high quality and moisture/air-resistant fi lms under ambient conditions. To examine the processability of perovskite fi lms in ambient and explore the effect of different coating methods on device performance, we have fabricated perovsktie solar cells using both spinand blade-coating. The fi lms were annealed at 90 °C in air for 2 h after both coating processes; but in the case of bladecoating, the wet fi lms formed immediately after solution blading were kept at room temperature for 40 min before annealing to wait for the majority of N,N -dimethylformamide (DMF) solvent to be evaporated. The same coating and annealing conditions were used for other perovskite fi lms studied later in this work. The device confi guration and energy band diagram of materials used in this study is shown in Figure 1 . [ 39,40 ]
333 citations
TL;DR: This work focuses on the electron selective contact in the perovskite solar cells and physical processes occurring at that heterojunction, and develops efficient devices by replacing the commonly employed TiO2 compact layer with fullerene C60 in a regular n-i-p architecture.
Abstract: Organic–inorganic halide perovskite solar cells have rapidly evolved over the last 3 years. There are still a number of issues and open questions related to the perovskite material, such as the phenomenon of anomalous hysteresis in current–voltage characteristics and long-term stability of the devices. In this work, we focus on the electron selective contact in the perovskite solar cells and physical processes occurring at that heterojunction. We developed efficient devices by replacing the commonly employed TiO2 compact layer with fullerene C60 in a regular n–i–p architecture. Detailed spectroscopic characterization allows us to present further insight into the nature of photocurrent hysteresis and charge extraction limitations arising at the n-type contact in a standard device. Furthermore, we show preliminary stability data of perovskite solar cells under working conditions, suggesting that an n-type organic charge collection layer can increase the long-term performance.
313 citations
TL;DR: Guo et al. as discussed by the authors developed a conventional PHJ PVSC with the confi guration of substrate/HTL (p)/perovskite (i)/fullerene derivative (n) has been developed.
Abstract: To surmount these obstacles, conventional PHJ PVSCs with the confi guration of substrate/HTL (p)/perovskite (i)/fullerene derivative (n) has been developed. [ 9 ] PEDOT:PSS or NiO X are the commonly employed HTLs to date while the electron-transporting layers (ETLs) employed are mainly based on fullerene derivatives. [ 7c,9c,d,10 ] It is worth noting that room temperature and orthogonal solvent processability of fullerene derivatives can successfully prevent the degradation of the underlying perovskite layer. In addition, the decent electron mobility of most fullerene derivatives makes them promising ETLs for high-performance PVSCs. Guo et al. fi rst demonstrated the feasibility of such a conventional PHJ confi guration, realizing a PCE of 3.9% by employing a phenyl-C 61 -butyric acid methyl ester (PC 61 BM) ETL. [ 9c ] Although three different fullerene derivatives (C 60 , PC 61 BM, and indene-C 60 bisadduct (IC 60 BA)) were investigated as ETLs, the functions of these fullerene-based interlayers were not fairly explored due to the inferior quality of the perovskite thin fi lm grown atop them. Soon after, a PC 61 BM ETL was used in a similar PHJ structure by Lam et al. to further improve the device performance to 7.4% by optimizing the perovskite precursor solution concentration and the blending ratio of PbI 2 and methylammonium iodide (MAI). [ 9a ] Lately, Jen and co-workers have signifi cantly enhanced the PCE to 12%–13%, respectively, by optimizing perovskite deposition either by controlling annealing conditions or adding a solvent additive.[11] Most recently, Seok and co-workers have reported an over 14% PCE through solvent engineering and thickness optimization of PC 61 BM. [ 12 ]
289 citations
TL;DR: In this paper, the authors investigated the feasibility of achieving fully printable perovskite solar cells by the blade-coating technique under the ambient condition, and they achieved a high performance with a PCE of 7.14% ± 0.31% for the first time using this low-temperature (<150 °C) fully-printable process.
Abstract: In order to fabricate large-area PVSCs, one of the critical challenges is to understand the infl uence of ambient environment on resultant perovskite thin-fi lms since perovskite crystals are sensitive to humidity under ambient condition. It has been shown that perovskite crystals degrade gradually when they are in contact with ambient moisture for certain time. [ 31,32 ] Therefore, most of the high performance perovskite solar cells are prepared in glovebox to avoid contacting moisture. However, fabricating PVSCs under ambient condition is inevitable if we desire to transition from laboratory research into large-scale applications. Lately, there are several encouraging reports about allowing limited amount of moisture to facilitate the perovskite crystallization and improve the performance of resulting device. [ 33,34 ] However, there are no detailed underlying mechanisms explained on how moisture affects perovskite crystallization so far. To alleviate these problems, we have investigated the feasibility of achieving fully printable PVSCs by the blade-coating technique under the ambient condition. The blade-coating fabrication has been widely used to fabricate OSCs and is proven to be a simple, environment-friendly, and low-cost method for the solution-processed photovoltaic. Compared to the screen printing, it not only can print nanoparticles, but also can print all kinds of solutions with any concentration. Moreover, the fi lm morphology control of the blade-coating method is much better than the spray coating and roll-to-roll printing; high-quality photoactive layers with controllable thickness can be accomplished by using a precisely translational blade under the ambient condition with controlled relative humidity. The PVSCs with a confi guration of ITO/poly(3,4-ethylenedioxy-thiophene):poly(4-styrenesulfonate) (PEDOT:PSS)/ CH 3 NH 3 PbI X Cl 3− X /[6,6]-phenyl-C 61 butyric acid methyl ester (PC 61 BM)/Bis-C 60 /Ag were fabricated to realize the fully printable process, as illustrated in Figure 1 a. All constituent interlayers, except for the Ag top electrode, were prepared via blade-coating. The coating conditions were optimized to allow the preparation of high-quality interlayer fi lms. Especially, the effect of humidity was carefully investigated and monitored to facilitate the crystallization of perovskite fi lms under ambient condition. Finally, high PCE (10.44% ± 0.23%) device could be achieved after optimizing the blade-coating process and relative humidity in environment. Moreover, a high-performance fl exible PVSC with a PCE of 7.14% ± 0.31% was demonstrated for the fi rst time using this low-temperature (<150 °C) fully printable process. The exceptional photovoltaic properties demonstrated recently for organic–inorganic halide perovskites (such as CH 3 NH 3 PbX 3 (X = Cl, Br, or I)) have attracted great attention from researchers. [ 1–8 ] The promising features of these perovskites include broad and intense absorption spectra, [ 9 ] appropriate semiconducting properties, [ 10 ] long carrier diffusion length, [ 11,12 ]
288 citations
220 citations
157 citations
TL;DR: In this paper, the additive can participate in the perovskite formation via dissociated halides, suggesting that molecular structure of alkyl halide additives plays multiple roles in modulating the dynamics of perovskiy crystal growth.
Abstract: Alkyl halide additives have been investigated to elucidate their effects in enhancing perovskite solar cell performance. We found that the additives can participate in the perovskite formation via dissociated halides, suggesting that molecular structure of alkyl halide additives plays multiple roles in modulating the dynamics of perovskite crystal growth.
TL;DR: In this paper, the authors proposed to replace Pb 2+ with Sn 2+ cation, which has the tendency to oxidize to Sn 4+ and thus p-dope the perovskite, displaying metallike conductivity.
Abstract: DOI: 10.1002/aenm.201400960 red-shift beyond 1000 nm by partially replacing Pb 2+ with Sn 2+ . [ 12,13 ] Notably, the Sn 2+ cation has the tendency to oxidize to Sn 4+ and thus p-dope the perovskite, displaying metal-like conductivity. [ 12a ] However, the PCEs of the Sn-based perovskite solar cells encounter great losses when increasing the fraction of Sn 2+ due to poor perovskite fi lm formation and the instability of Sn 2+ . [ 12–15 ] Currently, successful demonstrations of Pb 2+
TL;DR: In this paper, the influence of molecular geometry of the donor polymers and the perylene diimide dimers (di-PDIs) on the bulk heterojunction (BHJ) morphology in the nonfullerene polymer solar cells (PSCs) was investigated.
Abstract: In this study, we investigate the influence of molecular geometry of the donor polymers and the perylene diimide dimers (di-PDIs) on the bulk heterojunction (BHJ) morphology in the nonfullerene polymer solar cells (PSCs). The results reveal that the pseudo 2D conjugated poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th) has better miscibility with both bay-linked di-PDI (B-di-PDI) and hydrazine-linked di-PDI (H-di-PDI) compared to its 1D analog, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7), to facilitate more efficient exciton dissociation in the BHJ films. However, the face-on oriented - stacking of PTB7-Th is severely disrupted by the B-di-PDI due to its more flexible structure. On the contrary, the face-on oriented - stacking is only slightly disrupted by the H-di-PDI, which has a more rigid structure to provide suitable percolation pathways for charge transport. As a result, a very high power conversion efficiency (PCE) of 6.41% is achieved in the PTB7-Th:H-di-PDI derived device. This study shows that it is critical to pair suitable polymer donor and di-PDI-based acceptor to obtain proper BHJ morphology for achieving high PCE in the nonfullerene PSCs.
TL;DR: In this article, a versatile interconnecting layer based on reflective ultra-thin Ag (8-14 nm) was developed to enable the fabrication of a series-connected micro-cavity tandem polymer solar cell.
Abstract: A versatile interconnecting layer (ICL) based on reflective ultra-thin Ag (8–14 nm) was developed to enable the fabrication of a series-connected micro-cavity tandem polymer solar cell. This novel ICL can manipulate the optical field distribution between the constituent sub-cells to address the challenge of current matching. As a result, a very high power conversion efficiency (∼11%) and high summed external quantum efficiency of >90% were demonstrated.
TL;DR: A nonfullerene acceptor based on a 3D tetraperylene diimide is developed for bulk heterojunction organic photovoltaics and a significant improvement of power conversion efficiency can be achieved.
Abstract: A nonfullerene acceptor based on a 3D tetraperylene diimide is developed for bulk heterojunction organic photovoltaics. The disruption of perylene diimide planarity with a 3D framework suppresses the self-aggregation of perylene diimide and inhibits excimer formation. From planar monoperylene diimide to 3D tetraperylene diimide, a significant improvement of power conversion efficiency from 0.63% to 3.54% can be achieved.
TL;DR: Through further comparative studies of neat regioregular polymers based on each individual segment, it is identified the specific segment that contributes to the superior absorption, packing order, and charge mobility in the corresponding polymers.
Abstract: By studying the regio- and chemoselectivity of fluoro-substituted thienothiophene and benzodithiophene copolymers, we found polymers made from conventional one-pot polycondensation reaction consist of two distinctly different segments with a ratio of 0.36/0.64. Through further comparative studies of neat regioregular polymers based on each individual segment, we have identified the specific segment that contributes to the superior absorption, packing order, and charge mobility in the corresponding polymers. The unique structure–property relationships are the result of cooperative molecular arrangements of the key segment and noncovalent interaction between the fluoro group and the aromatic proton on the thiophene side-chain of the polymers.
TL;DR: The potential of low-temperature processed organic EEL to replace transition metal oxide-based interlayers for highly printing compatible PVSCs with high-performance is shown.
Abstract: In this work, we describe a room-temperature, solution-processable organic electron extraction layer (EEL) for high-performance planar heterojunction perovskite solar cells (PHJ PVSCs). This EEL is composed of a bilayered fulleropyrrolidinium iodide (FPI)-polyethyleneimine (PEIE) and PC61BM, which yields a promising power conversion efficiency (PCE) of 15.7% with insignificant hysteresis. We reveal that PC61BM can serve as a surface modifier of FPI-PEIE to simultaneously facilitate the crystallization of perovskite and the charge extraction at FPI-PEIE/CH3NH3PbI3 interface. Furthermore, the FPI-PEIE can also tune the work function of ITO and dope PC61BM to promote the efficient electron transport between ITO and PC61BM. Based on the advantages of room-temperature processability and decent electrical property of FPI-PEIE/PC61BM EEL, a high-performance flexible PVSC with a PCE ∼10% is eventually demonstrated. This study shows the potential of low-temperature processed organic EEL to replace transition metal oxide-based interlayers for highly printing compatible PVSCs with high-performance.
TL;DR: In this paper, four new molecular donors were reported using a D1-A-D2-A -D1 structure, where D1 is an oligiothiophene, A is a benzothiadiazole, and D2 is indacenodithieno[3,2-b]thiophene.
Abstract: Four new molecular donors are reported using a D1-A-D2-A-D1 structure, where D1 is an oligiothiophene, A is a benzothiadiazole, and D2 is indacenodithieno[3,2-b]thiophene. The resulting materials provide efficiencies as high as 6.5% in organic solar cells, without the use of solvent additives or thermal/solvent annealing. A strong correlation between the end group (D1-A) dipole moment and the fill factor (FF), mobility, and loss in the open-circuit voltage (VOC) is observed. Indacenodithieno[3,2-b]thiophene-fluorobenzothiadiazole-terthiophene (IDTT-FBT-3T) possesses the largest end group dipole moment, and in turn, has the highest mobility, FF, and power conversion efficiency in devices. It also has a similarly high VOC (0.95 V) to the other materials (0.93–0.99 V), despite possessing a much higher highest occupied molecular orbital (HOMO) energy level.
TL;DR: In this article, a hole-transporting layer (HTL)-free conventional perovskite/fullerene heterojunction thin-film PVSC was demonstrated, which achieved a PCE of >11% with a high open-circuit voltage (Voc) of 101 V.
Abstract: A high-performance hole-transporting layer (HTL)-free conventional perovskite/fullerene heterojunction thin-film PVSC was demonstrated We revealed that perovskite can modify the work function of ITO, leading to sufficient charge extraction efficiency at the ITO/perovskite interface Combined with the high conductivity of ITO, a PCE of >11% with a high open-circuit voltage (Voc) of 101 V was achieved
TL;DR: It is demonstrated how the structures of these complementary cyanine salts can be tuned to achieve highly ordered J-type supramolecular aggregate structures of heptamethine dyes in crystalline solids.
Abstract: An understanding of structure–property relationships in cyanine dyes is critical for their design and application. Anionic and cationic cyanines can be organized into complementary cyanine salts, offering potential building blocks to modulate their intra/intermolecular interactions in the solid state. Here, we demonstrate how the structures of these complementary salts can be tuned to achieve highly ordered J-type supramolecular aggregate structures of heptamethine dyes in crystalline solids.
TL;DR: A new way of graphically relating information is developed, allowing the simultaneous mapping of schematic kinetic relationships between all currently prevailing perovskite deposition and growth techniques.
Abstract: Organo-lead halide perovskite photovoltaics have developed faster than our understanding of the material itself. Using the vast body of work on perovskite processing created in just the past few years, it is possible to create a better picture of this material's complex phase-transformation behavior. This concept paper summarizes and correlates the current understanding of structural intermediates, kinetic controls, and structure-property relationships of organo-lead iodide perovskites. To this end, a new way of graphically relating information is developed, allowing the simultaneous mapping of schematic kinetic relationships between all currently prevailing perovskite deposition and growth techniques.
TL;DR: In this paper, a series of indacenodithiophene polymers and their selenium-substituted analogs are used as electron donor materials and fullerenes as acceptors.
Abstract: Using an analysis based on Marcus theory, we characterize losses in open-circuit voltage (VOC) due to changes in charge-transfer state energy, electronic coupling, and spatial density of charge-transfer states in a series of polymer/fullerene solar cells. We use a series of indacenodithiophene polymers and their selenium-substituted analogs as electron donor materials and fullerenes as the acceptors. By combining device measurements and spectroscopic studies (including subgap photocurrent, electroluminescence, and, importantly, time-resolved photoluminescence of the charge-transfer state) we are able to isolate the values for electronic coupling and the density of charge-transfer states (NCT), rather than the more commonly measured product of these values. We find values for NCT that are surprisingly large (∼4.5 × 1021–6.2 × 1022 cm–3), and we find that a significant increase in NCT upon selenium substitution in donor polymers correlates with lower VOC for bulk heterojunction photovoltaic devices. The inc...
TL;DR: In this article, a tetraene structure with a strong dialkylaminophenyl donor and a CF3-TCF acceptor is used as the primary chromophore due to its large hyperpolarizability, and a short cyanoacetate dye with a smaller dipole moment and a very different molecular aspect ratio for dipole engineering.
Abstract: A new design of tethered binary chromophores has been studied for nonlinear optics. In this work, a push–pull tetraene structure with a strong dialkylaminophenyl donor and a CF3-TCF acceptor is used as the primary chromophore due to its large hyperpolarizability, and a short cyanoacetate dye with a smaller dipole moment and a very different molecular aspect ratio is used as a secondary dipolar structure for dipole engineering. We found that such binary chromophore systems (exemplified as chromophore C1) exhibited significantly improved poling efficiency and thermal stability in poled films of guest–host polymers and monolithic glass. A systematic study of materials' physical properties, including analyses of poling-induced order thermally stimulated depolarization and comparison with simple dipolar polyenes, correlates the improved EO performance of poled films containing C1 well with its tethered binary structure. It provides an effective electrostatic screening mechanism for excellent solution processibility of materials, and a cooperative enhancement for higher polar order of poled thin films under the force of the applied poling field. An ultrahigh r33 value of 273 pm V−1 and a high refractive index of 2.12 at the wavelength of 1300 nm have been achieved for monolithic glass of C1, which represents a record-high n3r33 figure-of-merit of 2601 pm V−1 with good temporal stability. This exceptional result is a great demonstration of the advantages offered by dynamically assisted dipolar polarization enhancement of tethered binary chromophores, for significantly improving the poling efficiency and thermal stability of organic EO materials for efficient optical modulation.
TL;DR: In this article, a high performance ITO-free flexible polymer solar cell (PSC) is successfully described by integrating the plasmonic effect into the ITO free microcavity architecture.
Abstract: In this work, a high-performance ITO-free flexible polymer solar cell (PSC) is successfully described by integrating the plasmonic effect into the ITO-free microcavity architecture. By carefully controlling the sizes of embedded Ag nanoprisms and their doping positons in the stratified device, a significant enhancement in power conversion efficiency (PCE) is shown from 8.5% (reference microcavity architecture) to 9.4% on flexible substrates. The well-manipulated plasmonic resonances introduced by the embedded Ag nanoprisms with different LSPR peaks allow the complementary light-harvesting with microcavity resonance in the regions of 400–500 nm and 600–700 nm, resulting in the substantially increased photocurrent. This result not only signifies that the spectral matching between the LSPR peaks of Ag nanoprisms and the relatively low absorption response of photoactive layer in the microcavity architecture is an effective strategy to enhance light-harvesting across its absorption region, but also demonstrates the promise of tailoring two different resonance bands in a synergistic manner at desired wavelength region to enhance the efficiency of PSCs.
TL;DR: In this article, it was shown that a Peierls-type symmetry breaking that localizes charge on one end of the molecule will occur if L is greater than nine sp 2 hybridized carbon atoms (C9), resulting in losing this favorable characteristic optical property of cyanines.
Abstract: to the simplifi ed perturbation theory. [ 7 ] As is well known, the extension of conjugation length ( L ) of a cyanine will enhance the magnitude of Re( γ ) dramatically (i.e., Re( γ ) ∝ L n ). [ 8 ] However, a Peierls-type symmetry breaking that localizes charge on one end of the molecule will occur if L is greater than nine sp 2 hybridized carbon atoms (C9), resulting in losing this favorable characteristic optical property of cyanines. [ 9 ]
TL;DR: In this paper, direct arylation-derived diketopyrrolopyrrole (DPP)-based three-dimensional (3D) donors that can deliver respectable power conversion efficiencies (PCEs) of 4.64% and 4.02% with polymeric acceptor N2200 blends were explored.
Abstract: Non-fullerene acceptor based organic photovoltaic devices (OPVs) reported so far are inferior to those derived from fullerenes. This increases the speculation on whether donors need to be tailored for advancing non-fullerene OPVs. We explored herein two direct arylation-derived diketopyrrolopyrrole (DPP)-based three-dimensional (3D) donors that can deliver respectable power conversion efficiencies (PCEs) of 4.64% and 4.02% with polymeric acceptor N2200 blends, surpassing those obtained from PC71BM (3.56% and 3.22%, respectively). It is found that these 3D-shaped molecular donors can yield improved photo-to-current conversion and balanced charge transport when blending with the linear N2200 polymer. This finding suggests that engineering molecular geometry can be a promising approach for developing high-performance materials.
TL;DR: In this paper, a surface-normal plasmonic modulator using sub-wavelength metal grating is presented, which consists of a 1.77μm efficiently poled electro-optic polymer film, which is sandwiched between an indium-tin oxide film.
TL;DR: In-plane slotted patch antenna-coupled electro-optic phase modulators with a carrier-to-sideband ratio (CSR) of 22 dB under an RF power density of 120 W/m(2) and a figure of merit of 2.0 W(-1/2) at the millimeter wave frequencies of 36-37 GHz are reported.
Abstract: We report in-plane slotted patch antenna-coupled electro-optic phase modulators with a carrier-to-sideband ratio (CSR) of 22 dB under an RF power density of 120 W/m(2) and a figure of merit of 2.0 W(-1/2) at the millimeter wave frequencies of 36-37 GHz based on guest-host type of second-order nonlinear polymer SEO125. CSR was improved more than 20 dB by using a SiO(2) protection layer. We demonstrate detection of 3 GHz modulation of the RF carrier. We also derive closed-form expressions for the modulated phase of optical wave and carrier-to-sideband ratio. Design, simulation, fabrication, and experimental results are discussed.
TL;DR: In this article, a synergistic approach to modulate organic perovskite interfaces and their photovoltaic behaviors by tuning the properties of n-contact fullerenes layered atop of perovskiite was presented.
Abstract: We present a synergistic approach to modulate organic–perovskite interfaces and their photovoltaic behaviors by tuning the properties of n-contact fullerenes layered atop of perovskite. Fullerenes with excited charge transfer are found to not only suppress fullerene photoluminescence, but also enhance molecular polarization and transport capabilities. This results in optimized perovskite–fullerene contact.
TL;DR: This study uses an amphiphilic fullerene derivative soluble in methanol to form co-assemblies with insoluble fulleanne derivatives, pristine fullerenes, and metallofullerene via strong π-π interactions and all co- assemblies show metallic-like conductive properties with significantly enhanced conductivity compared to the pure amphiphiles.
Abstract: Supramolecular arrangement of conjugated molecules has crucial influence on their material properties. For fullerenes and metallofullerenes, tight and ordered packing is beneficial for intermolecular charge transport and energy transfer, but it is tricky to achieve, especially for functionalized cages due to the often extensive solvation and steric effects of functional groups. In this study, we use an amphiphilic fullerene derivative soluble in methanol to form co-assemblies with insoluble fullerene derivatives, pristine fullerene, and metallofullerene via strong π–π interactions. These mixtures are processable in methanol and show fullerene-templated crystalline structures in spin-cast films. Devices are successfully fabricated on a field-effect transistor platform with this approach, and all co-assemblies show metallic-like conductive properties with significantly enhanced conductivity compared to the pure amphiphilic fullerene derivative.