Description of the publication:


A. Iwan, A. Sikora, V. Hamplová, A. Bubnov


AFM study of advanced composite materials for organic photovoltaic cells with active layer based on P3HT:PCBM and chiral photosensitive liquid crystalline dopants


Liquid Crystals













AFM; chiral liquid crystal; organic solar cells; AZO compounds; photovoltaics


Advanced composite materials aimed for construction of organic photovoltaic cells have been studied by atomic force microscopy (AFM). The composites are based on poly(3-hexylthiophene) (P3HT), [6,6]-phenyl C61-butyric acid methyl ester (PCBM) and two different chiral photosensitive liquid crystalline (LC) materials. The objective 10 of the study was to examine the nanoscale morphology of the active layer without and after annealing at specific temperature. The preliminary results of AFM observation of the morphological changes done on the investigated composites revealed an increase in the surface ordering. The surface area ratio decreases for both studied composites, while the basic roughness parameters (Sa and Sq) have been found toughly dependent on the structure of the photosensitive LC dopant.


♦ Nemec H, Galoppini E, Imahori H. Sundstrom V. solar energy conversion - natural to artificial. Compr Nanosci Technol. 2011;2:325-359.
♦ Li G, Zhu R, Yang Y. Polymer solar cells. Nat Photon. 2012;6:153-161.
♦ Jayawardena KDGI, Rozanski LJ, Mills CA, Beliatis MJ, Nismy NA, Silva SRP. 'Inorganics-in-Organics': recent developments and outlook for 4G polymer solar cells. Nanoscale. 2013;5:8411-8427.
♦ Cai W, Gong X, Cao Y. Polymer solar cells: recent development and possible routes for improvement in the performance. Sol Energy Mater Sol C. 2010;94:114-127.
♦ Li YF. Molecular design of photovoltaic materials for polymer solar cells: toward suitable electronic energy levels and broad absorption. Acc Chem Res. 2012;45:723-733.
♦ Zhou H, Yang L, You W. Rational design of high performance conjugated polymers for organic solar cells. Macromolecules. 2012;45:607-632.
♦ Yuan K, Chen L, Chen Y. Photovoltaic performance enhancement of P3HT/PCBM solar cells driven by incorporation of conjugated liquid crystalline rod-coil block copolymers. J Mat Chem C. 2014;2:3835-3845.
♦ Heo SW, Baek KH, Song HJ, Lee TH, Moon DK. Improved performance of P3HT:PCBM-based solar cells using nematic liquid crystals as a processing additive under low processing temperature conditions. Macromol Mater Eng. 2014;299:353-360.
♦ Chen W, Chen Y, Li F, Chen L, Yuan K, Yao K, Wang P. Ordered microstructure induced by orientation behavior of liquid-crystal polythiophene for performance improvement of hybrid solar cells. Sol Energy Mater Sol C. 2012;96:266-.275.
♦ Palewicz M, Iwan A, Sibinski M, Sikora A, Mazurek B. Organic photovoltaic devices based on polyazomethine and fullerene. Energy Procedia. 2011;3:84-91.
♦ Yao K, Chen L, Hu T, Chen Y. Photocrosslinkable liquid.crystalline polymers for stable photovoltaics by adjusting side-chains spacing and fullerene size to control intercalation. Org Electron. 2012;13:1443-1455.
♦ Sun Q, Park KS, Dai L. Liquid crystalline polymers for efficient bilayer-bulk-heterojunction solar cells. J Phys Chem C. 2009;113:7892-7897.
♦ Schmidt-Mende L, Fechtenkotter A, Mullen K, Moons E, Friend RH, MacKenzie JD. Self-organized discotic liquid crystals for high-efficiency organic photovol- taics. Science. 2001;293:1119-1122.
♦ Myers SA, Al Kalifah MS, Lei C, OfNeill M, Kitney SP, Kelly SM. The influence of the nematic phase on the phase separation of blended organic semiconduc- tors for photovoltaics. Sol Energy Mater Sol C. 2013;116:262-269.
♦ Jung J, Rybak A, Slazak A, Bialecki S, Miskiewicz P, Glowacki I, Ulanski J, Rosselli S, Yasuda A, Nelles G, Tomovi.c.c , Watson MD, MullencK. Photogeneration and photovoltaic effect in blends of derivatives of hexabenzocoronene and perylene. Synth Met. 2005;155:150-156.
♦ Hirota K, Tajima K, Hashimoto K. Physicochemical study of discotic liquid crystal decacyclene derivative and utilization in polymer photovoltaic devices. Synth Met. 2007;157:290-296.
♦ Wang L, Park S-Y, Lee S-H, Lee E, Jeong K-U, Lee M-H. Bulk heterojunction photovoltaic cells based on room temperature liquid crystalline tetrathiafulvalene derivatives. Liq Cryst. 2012;39:795-801.
♦ Li L, Kang S-W, Harden J, Sun Q, Zhou X, Dai L, Jakli A, Kumar S, Li Q. Nature inspired light-harvesting liquid crystalline porphyrins for organic photovoltaics. Liq Cryst. 2008;35:233-239.
♦ Nhu T, Hoang Y, Pociecha D, Salamonczyk M, Gorecka E, Deschenaux R. A liquid-crystalline fullerene.oligophenylenevinylene dyad which displays columnar mesomorphism. Soft Matter. 2011;7:4948-4953.
♦ Zheng Q, Fang G, Bai W, Sun N, Qin P, Fan X, Cheng F, Yuan L, Zhao X. Efficiency improvement in organic solar cells by inserting a discotic liquid crystal. Sol Energy Mater Sol C. 2011;95:2200-2205.
♦ Jeong S, Kwon Y, Choi B-D, Ade H, Han YS. Improved efficiency of bulk heterojunction poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester photovoltaic devices using discotic liquid crystal additives. Appl Phys Lett. 2010;96:183305-1833053.
♦ Jeong S, Kwon Y, Choi B-D, Kwak G, Han YS. Effects of nematic liquid crystal additives on the performance of polymer solar cells. Macromol Chem Phys. 2010;211:2474-2479.
♦ Canli NY, GunescS, Pivrikas A, Fuchsbauer A, Sinwel D, Sariciftci N, Yasa Oc , Bilgin-Eran B-EB. Chiral (S)- 5-octyloxy-2-[{4-(2-methylbuthoxy)-phenylimino}- methyl]-phenol liquid crystalline compound as additive into polymer solar cells. Sol Energy Mater Sol C. 2010;94:1089-1099.
♦ Iwan A, Palewicz M, Krompiec M, Grucela-Zajac M, Schab-Balcerzak E. Synthesis, materials characterization and opto(electrical) properties of unsymmetrical azomethines with benzothiazole core. Spectrochim Acta Part A: Mole Biomole Spectr. 2012;97:546-555.
♦ Lincker F, Heinrich B, De Bettignies R, Rannou P, PecautcJ, GrevincB, Pron A, Donnio B, Demadrille R. Fluorenone core donor-acceptor-donor Î-conjugated molecules end-capped with dendritic oligo(thiophene)s: synthesis, liquid crystalline behaviour, and photovoltaic applications. J Mater Chem. 2011;21:5238-5247.
♦ Schmidt J, Dierking I. Localization and imaging of local shunts in solar cells using polymer-dispersed liquid crystals. Prog Photovoltaics. 2001;9:263-271.
♦ Mikroyannidis JA, Tsagkournos DV, Sharma SS, Kumar A, Vijay YK, Sharma GD. Efficient bulk heterojunction solar cells based on low band gap bisazo dyes containing anthracene and/or pyrrole units. Sol Energy Mater Sol C. 2010;94:2318-2327.
♦ Sharma GD, Mikroyannidis JA, Sharma SS, Justin Thomas KR. Bulk heterojunction organic photovoltaic devices based on small molecules featuring pyrrole and carbazole and 2-(4-nitrophenyl)acrylonitrile acceptor segments as donor and fullerene derivatives as acceptor. Dyes Pigm. 2012;94:320-329.
♦ Wang M, Chesnut E, Sun Y, Tong M, Guide M, Zhang Y, Treat ND, Varotto A, Mayer A, Chabinyc MLc , Nguyen T-Q, Wudl F. PCBM disperse-red ester with strong visible-light absorption: implication of molecular design and morphological control for organic solar cells. J Phys Chem C. 2012;116:1313-1321.
♦ Kim K-H, Yu H, Kang H, Kang DJ, Cho C-H, Cho-H-H, Oh JH, Kim BJ. Influence of intermolecular interactions of electron donating small molecules on their molecular packing and performance in organic electronic devices. J Mater Chem. 2013;1:14538-14547.
♦ Troshin PA, Susarova DK, Khakina EA, Goryachev AA, Borshchev OV, Ponomarenko SA, Razumov VF, 465 Sariciftci NS. Material solubility and molecular compatibility effects in the design of fullerene/polymer composites for organic bulk heterojunction solar cells. J Mater Chem. 2012;22:18433-18441.
♦ Wunsch BH, Rumi M, Tummala NR, Risko C, Kang D-Y, Steirer KX, Gantz J, Said M, Armstrong NR, Bredasc J-L, Bucknall D, Marder SR. Structure-processing-property correlations in solution-processed, small-molecule, organic solar cells. J Mater Chem C. 2013;1:5250-5260.
♦ Ka.par M, Bubnov A, Sedlakova Z, Stojanovi. M, Havli.ek J, Obadovi.cDZ, IlavskycM. Liquid crystalline polybutadiene diols with chiral thiol side-chain units. Eur Polym J. 2008;44:233-243.
♦ Novotna V, Hamplova V, Bubnov A, Ka.par M, Glogarova M, Kapernaum N, Bezner S, Giesselmann F. First photoresponsive liquid-crystalline materials with small layer shrinkage at the transition to the ferro- electric phase. J MatChem. 2009;19:3992-3997.
♦ Novotna V, Hamplova V, Ka.par M, Podoliak N, Bubnov A, Glogarova M, Nonnenmacher D, Giesselmann F. The effect of lactate unit number in compounds with azo group in the molecular core. Liq Cryst. 2011;38:649-655.
♦ Bobrovsky A, Shibaev V, Bubnov A, Hamplova V, Ka.par M, Glogarova M. Effect of molecular structure on chiro-optical and photo-optical properties of smart liquid crystalline polyacrylates. Macromolecules. 2013;46:4276-4284.
♦ Toth-KatonacT, Cigl M, Fodor-Csorba K, Hamplova V, Janossy I, Ka.par M, Vojtylova T, Hampl F, Bubnov A. Functional photochromic methylhydrosi-loxane-based side-chain liquid-crystalline polymers. Macromol Chem Phys. 2014;215:742-752.
♦ Bobrovsky A, Shibaev V, Elyashevitch G, Rosova E, Shimkin A, Shirinyan V, Bubnov A, Kasparc M, HamplovacV, GlogarovacM. New photosensitive polymer composites based on oriented porous polyethylene filled with azobenzene-containing LC mixture: reversible photomodulation of dichroism and birefringence. Liq Cryst. 2008;35:533-539.
♦ Iwan A, Boharewicz B, Tazbir I, Hamplova V, Bubnov A. Effect of chiral photosensitive liquid crystalline dopants on the performance of organic solar cells. Solid State Electron. 2015;104:53-60.
♦ Ka.par M, Bubnov A, Hamplova V, Pirkl S, Glogarova M. New ferroelectric liquid crystalline materials with an azo group in the molecular core. Liq Cryst. 2004;31:821-830.
♦ Henning A, Gunzburger G, Johr R, Rosenwaks Y, Bozic-Weber B, Housecroft CE, Constable EC, Meyer E, Glatzel T. Kelvin probe force microscopy of nanocrystalline TiO2 photoelectrodes. Beilstein J Nanotechnol. 2013;4:418-428.
♦ Sikora A, Bednarz L. Mapping of mechanical properties of the surface by utilization of torsional oscillation of the cantilever in atomic force microscopy. Cent Eur J Phys. 2011;9:372-379.
♦ Sikora A, Bednarz L. Dynamic speed control in atomic force microscopy to improve imaging time and quality. Meas Sci Technol. 2014;25:c044005.
♦ Sikora A, Bednarz L. The implementation and the performance analysis of the software based lock-in amplifier for the stiffness mapping with atomic force microscope (AFM). Bull Pol Acad Sci: Tech Sci. 2012;60:83-88.

Example figure:

3D view of the surface of the AZO sample.

Used methods: