Zakhidov, Anvar A.
Permanent URI for this collectionhttps://hdl.handle.net/10735.1/3178
Anvar Zakhidov is a professor of physics and a co-founder and Associate Director of the Alan G. MacDiarmid NanoTech Institute. Professor Zakhidov's main research fields are:
- Advanced Materials: Photonic Crystals, Nanostructured thermoelectrics. Carbon nanotubes and fullerenes. Nanotechnology: self-assembly, micro-templating
- Optoelectronics of organic & molecular solids: photocells, molecular electronic devices, OLEDs
- Spectroscopy of molecular crystals, conducting polymers, fullerenes, charge-transfer complexes, and organic ferromagnets
- MW spectroscopy of high-temperature, organic and fulleride superconductors
- Theory of low-dimensional organic solids, conducting polymers and fullerenes: properties of electronic excitations: excitons, polarons/bipolarons, solitons
Learn more about Dr. Zakhidov's research on his Faculty, NanoTech Institute, and Research Explorer pages.
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Elected 2020 fellow of the American Association for the Advancement of Science (AAAS) "for creative, pioneering contributions to the design, processing and understanding of functional nanomaterials, including carbon nanotubes, fullerenes and perovskites."
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Browsing Zakhidov, Anvar A. by Author "0000 0003 5287 0481 (Zakhidov, AA)"
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Item Effects of Nanostructure Geometry on Nanoimprinted Polymer Photovoltaics(RSC Pub, 2014-04-23) Yang, Yi; Mielczarek, Kamil; Aryal, Mukti; Zakhidov, Anvar A.; Hu, Wenchuang (Walter); 0000 0003 5287 0481 (Zakhidov, AA); 2005061514 (Hu, W); Zakhidov, Anvar A.; Hu, Wenchuang (Walter)We demonstrate the effects of nanostructure geometry on the nanoimprint induced poly(3-hexylthiophene-2,5-diyl) (P3HT) chain alignment and the performance of nanoimprinted photovoltaic devices. Out-of-plane and in-plane grazing incident X-ray diffraction techniques are employed to characterize the nanoimprint induced chain alignment in P3HT nanogratings with different widths, spacings and heights. We observe the dependence of the crystallite orientation on nanostructure geometry such that a larger width of P3HT nanogratings leads to more edge-on chain alignment while the increase in height gives more vertical alignment. Consequently, P3HT/6,6]-phenyl-C61-butyric-acid-methyl-ester (PCBM) solar cells with the highest density and aspect ratio P3HT nanostructures show the highest power conversion efficiency among others, which is attributed to the efficient charge separation, transport and light absorption.Item Electrochemically Gated Organic Photovoltaic with Tunable Carbon Nanotube Cathodes(2013-10-18) Cook, Alexander B.; Yuen, Jonathan D.; Zakhidov, Anvar A.; 0000 0003 5287 0481 (Zakhidov, AA); Zakhidov, Anvar A.We demonstrate an organic photovoltaic (OPV) device with an electrochemically gated carbon nanotube (CNT) charge collector. Bias voltages applied to the gate electrode reconfigure the common CNT electrode from an anode into a cathode which effectively collects photogenerated electrons, dramatically increasing all solar cell parameters to achieve a power conversion efficiency of ∼3%. This device requires very little current to initially charge and the leakage current is negligible compared to the photocurrent. This device can also be viewed as a hybrid tandem OPV-supercapacitor with a common CNT electrode. Other regimes of operation are briefly discussed.Item Halide-Perovskite Resonant Nanophotonics(Wiley-vch Verlag) Makarov, S.; Furasova, A.; Tiguntseva, E.; Hemmetter, A.; Berestennikov, A.; Pushkarev, A.; Zakhidov, Anvar A.; Kivshar, Y.; 0000 0003 5287 0481 (Zakhidov, AA); 0000-0003-3983-2229 (Zakhidov, AA); Zakhidov, Anvar A.Halide perovskites have emerged recently as promising materials for many applications in photovoltaics and optoelectronics. Recent studies of optical properties of halide perovskites suggest many novel opportunities for a design of advanced nanophotonic devices due to their low-cost fabrication, relatively high values of the refractive index, existence of excitons at room temperatures, broadband bandgap tunability, high optical gain, and strong nonlinear response, as well as simplicity of their integration with other types of optical and electronic structures. This paper provides an overview of the recent progress in the study of optical effects originating from nanostructured perovskites, and it also oversees a range of potential applications of resonant nanophotonics with halide perovskites.Item Lambertian White Top-Emitting Organic Light Emitting Device with Carbon Nanotube Cathode(2012-12-04) Freitag, P.; Zakhidov, Al A.; Luessem, B.; Zakhidov, Anvar A.; Leo, K.; 0000 0003 5287 0481 (Zakhidov, AA); Zakhidov, Anvar A.We demonstrate that white organic light emitting devices (OLEDs) with top carbon nanotube (CNT) electrodes show almost no microcavity effect and exhibit essentially Lambertian emission. CNT top electrodes were applied by direct lamination of multiwall CNT sheets onto white small molecule OLED stack. The devices show an external quantum efficiency of 1.5% and high color rendering index of 70. Due to elimination of the cavity effect, the devices show good color stability for different viewing angles. Thus, CNT electrodes are a viable alternative to thin semitransparent metallic films, where the strong cavity effect causes spectral shift and non-Lambertian angular dependence. Our method of the device fabrication is simple yet effective and compatible with virtually any small molecule organic semiconductor stack. It is also compatible with flexible substrates and roll-to-roll fabrication.Item Nanoimprinted Perovskite Metasurface for Enhanced Photoluminescence(Optical Soc Amer, 2018-11-05) Wang, Honglei; Liu, Shih-Chia; Balachandran, Balasubramaniam; Moon, Jiyoung; Haroldson, Ross; Li, Zhitong; Ishteev, Artur; Gu, Qing; Zhou, Weidong; Zakhidov, Anvar A.; Hu, Wenchuang (Walter); 0000 0003 5287 0481 (Zakhidov, AA); 0000-0003-3983-2229 (Zakhidov, AA); Wang, Honglei; Balachandran, Balasubramaniam; Moon, Jiyoung; Haroldson, Ross; Li, Zhitong; Gu, Qing; Zakhidov, Anvar A.; Hu, Wenchuang (Walter)Recently, solution-processed hybrid halide perovskite has emerged as promising materials for advanced optoelectronic devices such as photovoltaics, photodetectors, light emitting diodes and lasers. In the mean time, all-dielectric metasurfaces with high-index materials have attracted attention due to their low-loss and high-efficient optical resonances. Because of its tunable by composition band gap in the visible frequencies, organolead halide perovskite could serve as a powerful platform for realizing high-index, low-loss metasurfaces. However, direct patterning of perovskite by lithography-based technique is not feasible due to material instability under moisture. Here we report novel organolead halide perovskite metasurfaces created by the cost-effective thermal nanoimprint technology. The nanoimprinted perovskite metasurface showed improved surface morphology and enhanced optical absorption properties. Significantly enhanced optical emission with an eight-fold enhancement in photoluminescence (PL) intensity was observed under room temperature. Temperature-dependent PL of perovskite nanograting metasurface was also investigated. Based on our results, we believe that thermal nanoimprint is a simple and cost-effective technique to fabricate perovskite-based metasurfaces, which could have broad impact on optoelectronic and photonic applications.Item Room Temperature Operation of Directly Patterned Perovskite Distributed Feedback Light Source under Continuous-Wave Optical Pumping(Institute of Electrical and Electronics Engineers Inc.) Gharajeh, Abouzar; Haroldson, Ross; Li, Zhitong; Moon, Jiyoung; Balachandran, Balasubramaniam; Hu, Wenchuang (Walter); Zakhidov, Anvar A.; Gu, Qing; 0000 0003 5287 0481 (Zakhidov, AA); 0000-0003-3983-2229 (Zakhidov, AA); 0000-0003-3855-3690 (Gu, Q); Gharajeh, Abouzar; Haroldson, Ross; Li, Zhitong; Moon, Jiyoung; Balachandran, Balasubramaniam; Hu, Wenchuang (Walter); Zakhidov, Anvar A.; Gu, QingWe report the first directly patterned perovskite distributed feedback (DFB) resonator with a narrow amplified spontaneous emission (ASE) at pump powers as low as 0.1W/cm², under continuous-wave (CW) optical pumping condition at room temperature.Item Stable Doping of Carbon Nanotubes via Molecular Self Assembly(2014-10-13) Lee, B.; Chen, Y.; Cook, Alex; Zakhidov, Anvar A.; Podzorov, V.; 0000 0003 5287 0481 (Zakhidov, AA); Zakhidov, Anvar A.We report a novel method for stable doping of carbon nanotubes (CNT) based on methods of molecular self assembly. A conformal growth of a self-assembled monolayer of fluoroalkyl tri-chloro-silane (FTS) at CNT surfaces results in a strong increase of the sheet conductivity of CNT electrodes by 60-300%, depending on the CNT chirality and composition. The charge carrier mobility of undoped partially aligned CNT films was independently estimated in a field-effect transistor geometry (~100 cm² V⁻¹ s⁻¹). The hole density induced by the FTS monolayer in CNT sheets is estimated to be similar to 1.8 x 10¹⁴ cm⁻². We also show that FTS doping of CNT anodes greatly improves the performance of organic solar cells. This large and stable doping effect, easily achieved in large area samples, makes this approach very attractive for applications of CNTs in transparent and flexible electronics.Item Superconductivity in an inhomogeneous bundle of metallic and semiconducting nanotubes(2013-09-06) Grigorenko, I.; Zakhidov, Anvar A.; 0000 0003 5287 0481 (Zakhidov, AA); Zakhidov, Anvar A.Using Bogoliubov-de Gennes formalism for inhomogeneous systems, we have studied superconducting properties of a bundle of packed carbon nanotubes, making a triangular lattice in the bundle's transverse cross-section. The bundle consists of a mixture of metallic and doped semiconducting nanotubes, which have different critical transition temperatures. We investigate how a spatially averaged superconducting order parameter and the critical transition temperature depend on the fraction of the doped semiconducting carbon nanotubes in the bundle. Our simulations suggest that the superconductivity in the bundle will be suppressed when the fraction of the doped semiconducting carbon nanotubes will be less than 0.5, which is the percolation threshold for a two-dimensional triangular lattice.Item Tunable Hybrid Fano Resonances in Halide Perovskite Nanoparticles(American Chemical Society) Tiguntseva, E. Y.; Baranov, D. G.; Pushkarev, A. P.; Munkhbat, B.; Komissarenko, F.; Franckevičius, M.; Zakhidov, Anvar A.; Shegai, T.; Kivshar, Y. S.; Makarov, S. V.; 0000 0003 5287 0481 (Zakhidov, AA); 0000-0003-3983-2229 (Zakhidov, AA); Zakhidov, Anvar A.Halide perovskites are known to support excitons at room temperatures with high quantum yield of luminescence that make them attractive for all-dielectric resonant nanophotonics and meta-optics. Here we report the observation of broadly tunable Fano resonances in halide perovskite nanoparticles originating from the coupling of excitons to the Mie resonances excited in the nanoparticles. Signatures of the photon-exciton ("hybrid") Fano resonances are observed in dark-field spectra of isolated nanoparticles, and also in the extinction spectra of aperiodic lattices of such nanoparticles. In the latter case, chemical tunability of the exciton resonance allows reversible tuning of the Fano resonance across the 100 nm bandwidth in the visible frequency range, providing a novel approach to control optical properties of perovskite nanostructures. The proposed method of chemical tuning paves the way to an efficient control of emission properties of on-chip-integrated light-emitting nanoantennas. © 2018 American Chemical Society.Item Tunable Organic PV Parallel Tandem with Ionic Gating(Amer Inst Physics, 2018-10-22) Saranin, Danila; Ishteev, Artur; Cook, Alexander B.; Yuen, Jonathan D.; Kuznetsov, Denis; Orlova, Marina; Didenko, Sergey; Zakhidov, Anvar; 0000 0003 5287 0481 (Zakhidov, AA); 0000-0003-3983-2229 (Zakhidov, AA); Cook, Alexander B.; Yuen, Jonathan D.; Zakhidov, AnvarA novel type of tunable organic photovoltaic (OPV) tandem device with ionic gating by in-situ ionic liquid is presented. This device is comprised of two solution-processed polymeric OPV cells connected in parallel by a dry-laminated transparent multiwall carbon nanotube (MWCNT) interlayer. The interlayer MWCNT of this 3-terminal tandem device plays a role of a common electrode with a Fermi level that can be tuned via ionic gating to turn it into a common cathode, collecting photo-generated electrons from both sub-cells. Ionic gating employs electric double layer charging of the MWCNT in order to lower the work function of the common CNT electrode and increase its n-type conductivity. This tandem device is fabricated in ambient conditions via dry-lamination of MWCNT transparent sheets The new results demonstrating the different regimes of ionic gating at low, medium, and high gating voltages V_{gate} are presented, showing the optimal doping of the MWCNT, then favorable doping of acceptor PCBM ([6,6]-phenyl-C₆₁-butyric acid methyl ester), followed by the deterioration of performance at V_{gate} over the threshold voltage when doping of polymeric layers of sub-cell OPVs starts taking place. The doping of PCBM and polymers is additionally confirmed by the change in the charging and discharging current dynamics at high V_{gate} above the threshold.