Search

Charge separation dynamics after the absorption of a photon is a fundamental process relevant both for photosynthetic reaction centers and artificial solar conversion devices. It has been proposed that quantum coherence plays a role in the formation of charge carriers in organic photovoltaics, but experimental proofs have been lacking. Here we report experimental evidence of coherence in the charge separation process in organic donor/acceptor heterojunctions, in the form of low frequency oscillatory signature in the kinetics of the transient absorption and nonlinear two-dimensional photocurrent spectroscopy. The coherence plays a decisive role in the initial ~200 femtoseconds as we observe distinct experimental signatures of coherent photocurrent generation. This coherent process breaks the energy barrier limitation for charge formation, thus competing with excitation energy transfer. The physics may inspire the design of new photovoltaic materials with high device performance, which explore the quantum effects in the next-generation optoelectronic applications., Although coherent vibrational motion in donor-acceptor blends may contribute to photogeneration generation in organic solar cells (OSCs), proof of a direct correlation is still lacking. Here, the authors report the role of vibrational coherence on photocurrent generation in ternary OSC blends.

The hybrid metal halide perovskites have shown enormous promise for optoelectronic devices, including efficient photovoltaics, however their insensitivity to defects has remained puzzling. Polaron correlations have been cited as a possible means to protect charge carriers from defect scattering. In this paper, we show time-resolved THz spectroscopy measurements are capable of directly probing polaron correlations via an intra-band coherent beat arising from center-of-mass quasi-particle motion and the internal motion of charge within its self-induced potential. We describe these measurements indicating that charge carriers do indeed exist as polarons, which are coherent for several hundred femtoseconds following photon absorption.

We report pulsed terahertz (THz) emission from solution-processed metal halide perovskite films with electric field 1 order of magnitude lower than p-InAs, an efficient THz emitter. Such emission is enabled by a unique combination of efficient charge separation, high carrier mobilities, and more importantly surface defects. The mechanism of generation was identified by investigating the dependence of the THz electric field amplitude on surface defect densities, excess charge carriers, excitation intensity and energy, temperature, and external electric field. We also show for the first time THz emission from a curved surface, which is not possible for any crystalline semiconductor and paves the way to focus high-intensity sources. These results represent a possible new direction for perovskite optoelectronics and for THz emission spectroscopy as a complementary tool in investigating surface defects on metal halide perovskites, of fundamental importance in the optimization of solar cells and light-emitting diodes. Funding Agencies|ERC Starting Grant [717026]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; European Union Marie Curie ITN Project NOTEDEV [607521]; China Scholarship Council; Knut and Alice Wallenberg Foundation (KAW); Swedish Foundation for Strategic Research (SSF) [RIF14-055]

Cellulose-based helices retrieved from the plant celery with a conductive poly(4-(2,3-dihydrothieno [3,4-b]-[1,4]dioxin-2-yl-methoxy)-1-butanesulfonate (PEDOT-S). A resonance close to 1 THz and a broad shoulder that extends to 3.5 THz was obtained, consistent with electromagnetic models. As helical antennas, it was shown that both axial and normal modes are present, which are correlated to the orientation and antenna electrical lengths of the coated helices. This work opens the possibility of designing tunable terahertz antennas through simple control of their dimensions and orientation.

Although significant improvements have been achieved for organic photovoltaic cells (OPVs), the top-performing devices still show power conversion efficiencies far behind those of commercialized solar cells. One of the main reasons is the large driving force required for separating electron-hole pairs. Here, we demonstrate an efficiency of 14.7% in the single-junction OPV by using a new polymer donor PTO2 and a nonfullerene acceptor IT-4F. The device possesses an efficient charge generation at a low driving force. Ultrafast transient absorption measurements probe the formation of loosely bound charge pairs with extended lifetime that impedes the recombination of charge carriers in the blend. The theoretical studies reveal that the molecular electrostatic potential (ESP) between PTO2 and IT-4F is large, and the induced intermolecular electric field may assist the charge generation. The results suggest OPVs have the potential for further improvement by judicious modulation of ESP.

Photoinitiated charge carrier dynamics in ZnO nanoparticles sensitized by CdSe quantum dots is studied using transient absorption spectroscopy and time-resolved terahertz spectroscopy. The evolution of the transient spectra shows that electron injection occurs in a two-step process, where the formation of a charge transfer state (occurring in several picoseconds) is followed by its dissociation within tens of picoseconds. The photoconductivity of electrons injected into the ZnO nanoparticles is lower than that of charges photogenerated directly in ZnO. We conclude that the motion of injected electrons in ZnO nanoparticles is strongly influenced by their interaction with positive charges left in the sensitizing quantum dots. the Owner Societies 2017. This work was supported by the Knut and Alice Wallenberg Foundation, Swedish Research Council, Czech Science Foundation (Grant 17-03662S) and Carl Tryggers Foundation in Stockholm (Project CTS 14:390). KZ acknowledges support from NPRP grant #NPRP7-227-1-034 from the Qatar National Research Fund (a member of Qatar Foundation). Scopus

Ultrafast charge carrier dynamics in organo metal halide perovskite has been probed using time resolved terahertz (THz) spectroscopy (TRTS). Current literature on its early time characteristics is unanimous: sub-ps charge carrier generation, highly mobile charges and very slow recombination rationalizing the exceptionally high power conversion efficiency for a solution processed solar cell material. Electron injection from MAPbI3 to nanoparticles (NP) of TiO2 is found to be sub-ps while Al2O3 NPs do not alter charge dynamics. Charge transfer to organic electrodes, Spiro-OMeTAD and PCBM, is sub-ps and few hundreds of ps respectively, which is influenced by the alignment of energy bands. It is surmised that minimizing defects/trap states is key in optimizing charge carrier extraction from these materials.

Despite the unprecedented interest in organic-inorganic metal halide perovskite solar cells, quantitative information on the charge transfer dynamics into selective electrodes is still lacking. In this paper, we report the time scales and mechanisms of electron and hole injection and recombination dynamics at organic PCBM and Spiro-OMeTAD electrode interfaces. On the one hand, hole transfer is complete on the subpicosecond time scale in MAPbI3/Spiro-OMeTAD, and its recombination rate is similar to that in neat MAPbI3. This was found to be due to a high concentration of dark charges, i.e., holes brought about by unintentional p-type doping of MAPbI3. Hence, the total concentration of holes in the perovskite is hardly affected by optical excitation, which manifested as similar decay kinetics. On the other hand, the decay of the photoinduced conductivity in MAPbI3/PCBM is on the time scale of hundreds of picoseconds to several nanoseconds, due to electron injection into PCBM and electron-hole recombination at the interface occurring at similar rates. These results highlight the importance of understanding the role of dark carriers in deconvoluting the complex photophysical processes in these materials. Moreover, optimizing the preparation processes wherein undesired doping is minimized could prompt the use of organic molecules as a more viable electrode substitute for perovskite solar cell devices.

Solar energy conversion in photovoltaics or photocatalysis involves light harvesting, or sensitization, of a semiconductor or catalyst as a first step. Rare elements are frequently used for this purpose, but they are obviously not ideal for large-scale implementation. Great efforts have been made to replace the widely used ruthenium with more abundant analogues like iron, but without much success due to the very short-lived excited states of the resulting iron complexes. Here, we describe the development of an iron-nitrogen-heterocyclic-carbene sensitizer with an excited-state lifetime that is nearly a thousand-fold longer than that of traditional iron polypyridyl complexes. By the use of electron paramagnetic resonance, transient absorption spectroscopy, transient terahertz spectroscopy and quantum chemical calculations, we show that the iron complex generates photoelectrons in the conduction band of titanium dioxide with a quantum yield of 92% from the (3)MLCT (metal-to-ligand charge transfer) state. These results open up possibilities to develop solar energy-converting materials based on abundant elements.

Polarons in CH3NH3PbI3 are observed by terahertz spectroscopy showing coherent motion of charges coupled with lattice vibrations., Hybrid organic-inorganic halide perovskites have shown remarkable optoelectronic properties, exhibiting an impressive tolerance to defects believed to originate from correlated motion of charge carriers and the polar lattice forming large polarons. Few experimental techniques are capable of directly probing these correlations, requiring simultaneous sub–millielectron volt energy and femtosecond temporal resolution after absorption of a photon. Here, we use time-resolved multi-THz spectroscopy, sensitive to the internal excitations of the polaron, to temporally and energetically resolve the coherent coupling of charges to longitudinal optical phonons in single-crystal CH3NH3PbI3 (MAPI). We observe room temperature intraband quantum beats arising from the coherent displacement of charge from the coupled phonon cloud. Our measurements provide strong evidence for the existence of polarons in MAPI at room temperature, suggesting that electron/hole-phonon coupling is a defining aspect of the hybrid metal-halide perovskites contributing to the protection from scattering and enhanced carrier lifetimes that define their usefulness in devices.

Fluorescence super-resolution microscopy showed correlated fluctuations of photoluminescence intensity and spatial localization of individual perovskite (CH3NH3PbI3) nanocrystals of size ∼200 × 30 × 30 nm(3). The photoluminescence blinking amplitude caused by a single quencher was a hundred thousand times larger than that of a typical dye molecule at the same excitation power density. The quencher is proposed to be a chemical or structural defect that traps free charges leading to nonradiative recombination. These trapping sites can be activated and deactivated by light.

Hybrid metal-organic perovskite solar cells have astounded the solar cell community with their rapid rise in efficiency over the past three years. Despite this success, the basic processes governing the photogeneration of free charges, particularly their dynamics and efficiency, remain unknown. Here we use ultrabroadband pulses of THz frequency light to see the intrinsic photophysical properties of single crystal lead halide perovskite just femtoseconds after a photon is first absorbed. Our spectra reveal the dynamics and efficiencies of free charge creation, the remarkable ease in which they move through the lattice and the complicated interplay between free and bound charges in these materials.

A complete characterization of solar energy conversion devices and the processes underlying their function is a challenge, and require a multitude of different experimental methods. This chapter discusses investigations of molecular solar cells and solar fuels devices by time-resolved laser spectroscopic methods. These methods have established important concepts we now use for understanding the function of devices for solar energy conversion into primary products. We give examples of scientific insight provided by ultrafast methods using detection in the regions from X-ray to THz radiation, and particularly highlight the case where the use of different methods has provided complementary information. Charge collection and solar fuel catalysis on the other hand occur on longer time scales, which opens for the use of time-resolved magnetic resonance and microwave conductivity methods. We also point out that, with suitable precautions, time-resolved laser spectroscopy is able to give information relevant for in operando device conditions.

Electrons are the workhorses of solar energy conversion. Conversion of the energy of light to electricity in photovoltaics, or to energy-rich molecules (solar fuel) through photocatalytic processes, invariably starts with photoinduced generation of energy-rich electrons. The harvesting of these electrons in practical devices rests on a series of electron transfer processes whose dynamics and efficiencies determine the function of materials and devices. To capture the energy of a photogenerated electron-hole pair in a solar cell material, charges of opposite sign have to be separated against electrostatic attractions, prevented from recombining and being transported through the active material to electrodes where they can be extracted. In photocatalytic solar fuel production, these electron processes are coupled to chemical reactions leading to storage of the energy of light in chemical bonds. With the focus on the ultrafast time scale, we here discuss the light-induced electron processes underlying the function of several molecular and hybrid materials currently under development for solar energy applications in dye or quantum dot-sensitized solar cells, polymer-fullerene polymer solar cells, organometal halide perovskite solar cells, and finally some photocatalytic systems.

Solar cells based on organometal halide perovskites have seen rapidly increasing efficiencies, now exceeding 15%. Despite this progress, there is still limited knowledge on the fundamental photophysics. Here we use microwave photoconductance and photoluminescence measurements to investigate the temperature dependence of the carrier generation, mobility, and recombination in (CH3NH3)PbI3. At temperatures maintaining the tetragonal crystal phase of the perovskite, we find an exciton binding energy of about 32 meV, leading to a temperature-dependent yield of highly mobile (6.2 cm(2)/(V s) at 300 K) charge carriers. At higher laser intensities, second-order recombination with a rate constant of gamma = 13 x 10(-10) cm(3) s(-1) becomes apparent. Reducing the temperature results in increasing charge carrier mobilities following a T-1.6 dependence, which we attribute to a reduction in phonon scattering (Sigma mu = 16 cm(2)/(V s) at 165 K). Despite the fact that Sigma mu increases, gamma diminishes with a factor six, implying that charge recombination in (CH3NH3)PbI3 is temperature activated. The results underline the importance of the perovskite crystal structure, the exciton binding energy, and the activation energy for recombination as key factors in optimizing new perovskite materials.

Organometal halide perovskite-based solar cells have recently been reported to be highly efficient, giving an overall power conversion efficiency of up to 15%. However, much of the fundamental photophysical properties underlying this performance has remained unknown. Here, we apply photoluminescence, transient absorption, time-resolved terahertz and microwave conductivity measurements to determine the time scales of generation and recombination of charge carriers as well as their transport properties in solution-processed CH3NH3PbI3 perovskite materials. We found that electron-hole pairs are generated almost instantaneously after photoexcitation and dissociate in 2 ps forming highly mobile charges (25 cm(2) V(-1) s(-1)) in the neat perovskite and in perovskite/alumina blends; almost balanced electron and hole mobilities remain very high up to the microsecond time scale. When the perovskite is introduced into a TiO2 mesoporous structure, electron injection from perovskite to the metal oxide is efficient in less than a picosecond, but the lower intrinsic electron mobility of TiO2 leads to unbalanced charge transport. Microwave conductivity measurements showed that the decay of mobile charges is very slow in CH3NH3PbI3, lasting up to tens of microseconds. These results unravel the remarkable intrinsic properties of CH3NH3PbI3 perovskite material if used as light absorber and charge transport layer. Moreover, finding a metal oxide with higher electron mobility may further increase the performance of this class of solar cells.

The low-frequency spectra of normal anthracene and anthracene-d10 in the solid state were measured by a high-resolution terahertz spectrometer. We observed the isotope shift of the vibrational freq...

Photoinduced electron injection dynamics from CdSe quantum dots to ZnO nanowires is studied by transient absorption and time-resolved terahertz spectroscopy measurements. Ultrafast electron transfer from the CdSe quantum dots to ZnO is proven to be efficient already on a picoseconds time scale (τ = 3-12 ps). The measured kinetics was found to have a two-component character, whose origin is discussed in detail. The obtained results suggest that electrons are injected into ZnO via an intermediate charge transfer state.

We report experimental work on the terahertz emission characteristics of InAs/GaAs quantum dot (QD) structures and GaAs/AlGaAs modulation-doped heterojunctions (MDH’s), excited by femtosecond laser. Results showed that the terahertz emission from MDH’s can provide information on the GaAs/AlGaAs interface quality while the QD structures have the potential for being intense terahertz emitters; rivaling the emission intensity of p-type bulk InAs.

Organo-metal halide perovskites (OMHPs) have attracted enormous interest in recent years as materials for application in optoelectronics and solar energy conversion. These hybrid semiconductors seem to have the potential to challenge traditional silicon technology. In this review we will give an account of the recent development in the understanding of the fundamental light-induced processes in OMHPs from charge-photo generation, migration of charge carries through the materials and finally their recombination. Our and other literature reports on time-resolved conductivity, transient absorption and photoluminescence properties are used to paint a picture of how we currently see the fundamental excited state and charge-carrier dynamics. We will also show that there is still no fully coherent picture of the processes in OMHPs and we will indicate the problems to be solved by future research.

We report on studies of the formamidinium lead triiodide (FAPbI3) perovskite film using time-resolved terahertz (THz) spectroscopy (TRTS) and flash photolysis to explore charge carriers generation, migration, and recombination. The TRTS results show that upon femtosecond excitation above the absorption edge, the initial high photoconductivity (∼75 cm(2) V(-1) s(-1)) remains constant at least up to 8 ns, which corresponds to a diffusion length of 25 μm. Pumping below the absorption edge results in a mobility of 40 cm(2) V(-1) s(-1) suggesting lower mobility of charge carriers located at the bottom of the conduction band or shallow sub-bandgap states. Furthermore, analysis of the THz kinetics reveals rising components of1 and 20 ps, reflecting dissociation of excitons having different binding energies. Flash photolysis experiments indicate that trapped charge carriers persist for milliseconds.

The need for developing highly efficient solar cell devices have never been so pressing until recently when the urgency of using renewable energy sources becomes more evident. There are several promising technologies being explored by many groups with the sole purpose of optimizing harvesting sunlight and converting it to useful electricity. These include, but not limited to, dye- and quantum dot-sensitized, bulk heterojunction organic, inorganic nanowires, and very recently perovskite-based solar cells. In this talk, charge carrier dynamics of an assortment of solar cell technologies probed using time-resolved terahertz spectroscopy will be presented. Electron injection, mobility, charge carrier lifetime and recombination dynamics will be discussed.

We present terahertz (THz) emission of optically pumped 5-nm GaAs/AlGaAs multiple quantum wells (MQWs) even at excitation energies below the bandgap. The excitation energy corresponding to the peak THz emission is red-shifted with respect to the photoluminescence (PL) and photoluminescence excitation peak. This is attributed to a transient bandgap renormalization that occurs on the same time scale as the generation of the THz transients. Moreover, an emission shoulder at ∼40 meV below the THz emission peak was observed. Deep level transient spectroscopy results do not indicate that this is due to electron traps. However, an indistinct LO phonon-related, below-bandgap PL feature was seen at low temperature that coincides well with the observed THz radiation feature. It is proposed that the THz action spectrum may be sensitive to phonon-mediated processes in contrast to more conventional optical spectroscopy techniques, albeit at room temperature.

A method to decorate cellulose-based helices retrieved from the plant celery with a conductive polymer is proposed. Using a layer-by-layer method, the decoration of the polyanionic conducting polym ...

We analyzed ultrafast photocarrier generation in single crystal CH 3 NH 3 PbI 3 perovskite through time-resolved terahertz spectroscopy. We find a Drude-Lorentz type conductivity spectra with a carrier mobility of 35 cm2/Vs and a Lorentzian component at 45 meV possibly due to intra-excitonic transitions.

Waveguiding of excitation beam and propagation of THz beam in a complex gradient environment were studied in an array of InP nanowires. Measurements by time-resolved THz spectroscopy accompanied by Monte-Carlo calculations of the response of localized charges enabled determination of transversal electron mobility.

Terahertz spectroscopy is employed for the noncontact measurement of transversal mobility in InP nanowires, wherein photonic effects (waveguiding of excitation beam and propagation of terahertz beam in a complex gradient environment) were successfully deconvoluted. Monte Carlo calculations accounting for electron localization and heavy doping were used to determine electron momentum relaxation time corresponding to electron mobility >= 3000 cm(2)/Vs, which is similar to that in bulk InP. The developed approach paves a way for noncontact determination of charge mobility in advanced semiconductor nanostructures.

In this paper we studied carrier drift dynamics in APFO3:PC61BM solar cells of varied stoichiometry (2:1, 1:1, and 1:4 APFO3:PC61BM) over a wide time range, from subpicoseconds to microseconds with a combination of ultrafast optical electric field probing and conventional transient integrated photocurrent techniques. Carrier drift and extraction dynamics are strongly stoichiometry dependent: the speed of electron or hole drift increases with higher concentration of PC61BM or polymer, respectively. The electron extraction from a sample with 80% PC61BM takes place during hundreds of picoseconds, but slows down to sub-microseconds in a sample with 33% PC61BM. The hole extraction is less stoichiometry dependent: it varies form sub-nanoseconds to tens of nanoseconds when the PC61BM concentration changes from 33% to 80%. The electron extraction rate correlates with the conversion efficiency of solar cells, leading to the conclusion that fast electron motion is essential for efficient charge carrier separation preventing their geminate recombination.

Using terahertz and transient absorption spectroscopy, carrier dynamics in organo halide perovskite solar cell is probed. Charge generation is

The few-picosecond (ps) decay of terahertz (THz) photoconductivity typically observed for conjugated polymer fullerene blends (at excitation fluencies similar to 10(15) photons/cm(2) per pulse) is shown to be a result of charge pair annihilation for two polymer:PCBM blends. At a factor of 100 lower excitation density, the THz decay is in the hundreds of ps time scale, implying that very high carrier mobility (similar to 0.1 cm(2) V-1 s(-1)) prevails for long time after charge formation, of importance for free charge formation in organic solar cells.

Time-resolved terahertz spectroscopy was employed for the investigation of charge-transport dynamics in benzothiadiazolo-dithiophene polyfluorene ([2,7-(9,9-dioctylfluorene)- alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]) (APFO-3) polymers with various chain lengths and in its monomer form, all blended with an electron acceptor ([6,6]- phenyl-C61-butyric acid methyl ester, PCBM). Upon photoexcitation, charged polaron pairs are created, negative charges are transferred to fullerenes, while positive polarons remain on polymers/monomers. Vastly different hole mobility in polymer and monomer blends allows us to distinguish the hole and electron contributions to the carrier mobility.

Multiscale atomistic simulations were used to. understand the factors that determine the charge carrier mobility spectrum obtained from time-resolved terahertz (THz) spectroscopy in conjugated polymers. The simulation approach combines classical molecular dynamics simulations of atomic structure, large-scale electronic structure calculations, and the evaluation of the THz mobility using Kubo's linear response formula. We found that THz radiation probes a single carrier hop at low temperatures and high frequencies, while the transport over somewhat longer distances is probed in the opposite cases. Our results indicate that charge carrier transport at THz frequencies is thermally activated but with a much smaller activation energy compared to the dc case. The shape of the real and imaginary part of the mobility spectral curve reveals the presence of above THz hopping rates that are relevant for charge carrier transport. Strong differences of the mobilities in the polymer and the corresponding monomer material are largely caused by stronger energetic disorder of the monomer material. (Less)

Charge generation, injection and recombination in quantum dot-sensitized ZnO nanowires was probed using time resolved terahertz spectroscopy. The mobility spectrum at different representative pump-probe delays showed similar behavior during the injection time indicating free charges on the nanowire structures.

The optical properties and transient dynamics of ZnSe were studied by terahertz time-domain spectroscopy (THz-TDS) and optical-pump terahertz probe (OPTP) spectroscopy, respectively. From the THz time-domain signal, the frequency-dependent absorption coefficient and index of refraction of ZnSe were calculated. It follows that the values appear to be similar with those in literatures. The complex permittivity and conductivity of ZnSe were then derived. It was found out that ZnSe exhibit a more dominant dielectric response by the Jonscher's model. It was also noted that the Drude model did not fit the conductivity data. A UV-pump pulse was introduced to observe the transient dynamics. ZnSe has a faster charge carrier relaxation compared with Si and Ge.

By terahertz (THz) time-domain spectroscopy we have measured low-frequency spectra of amino acid (glycine; Gly), short peptides ((Gly)3and (Gly)4), six globular proteins and bacteriorhodopsin (BR). From the analysis of the THz spectra we defined and obtained the reduced absorption cross sections for these cases, which are proportional to the vibrational density of states. We observed anharmonic behaviors in the low-frequency modes of the short peptides. The globular proteins we investigated show a universal feature in the low-frequency spectra. BR shows the dynamical transition in the temperature dependence of the THz spectrum when the sample is hydrated.

Low-frequency spectra of amino acids and peptides of L-alanine and glycine were analyzed from the power law behavior of its absorption cross section. For amino acids the exponent around two were observed and interpreted as a collection of harmonic vibrations. However for peptides with longer chain i.e. (Gly) 4 and (L-ala) 5 exponents were reduced to 1.43 and 1.34, respectively. This behavior shows chain length dependence of the low frequency dynamics.

Birefringence was observed for a beta-BaB2O4 crystal in the 0.1 to 1.1 terahertz region. The calculated Deltan value was ~0.296. Moreover, an angle-dependent absorption band observed at ~0.65 terahertz is attributed to low-frequency phonon modes.

Nd3+: (La1-x, Bax)F3-x as new scintillator and laser material is explored using efficient micro-PD method. Fluorescence peak located at 175 nm is better compared to Nd3+:LaF3 due to broader fluorescence and shorter VUV transmission edge.

Azimuthal angle dependence of the terahertz radiation of (100) p-type InAs under 1-T field is presented. Four-fold symmetry for p-polarized radiation emerged and the same is seen for the s-polarized radiation for the no-field case.

Nd3+:(La1-x Bax)F3-x as new scintillator and laser material is explored using efficient micro-PD method. Fluorescence peak located at 175 nm is better compared to Nd3+:LaF3 due to broader fluorescence and shorter VUV transmission edge.

Nd3+: (La1-x,Bax)F3-x as new scintillator and laser material is explored using efficient micro-PD method. Fluorescence peak located at 175 nm is better compared to Nd3+:LaF3 due to broader fluorescence and shorter VUV transmission edge.

The design of a lens duct to facilitate the launching of terahertz (THz) radiation into Teflon photonic crystal fiber waveguide is presented. The InAs THz emitter, lens duct, and waveguide, collectively called THz pigtail are found to be potential mean of effectively channeling and directing THz radiation.