Efficient Inorganic–Organic Hybrid Perovskite Solar Cells Based on Pyrene Arylamine Derivatives as Hole-Transporting Materials

Jeon, Nam Joong,Lee, Jaemin,Noh, Jun Hong,Nazeeruddin, Mohammad Khaja,Grä,tzel, Michael,Seok, Sang Il American Chemical Society 2013 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.135 No.51

<P>A set of three <I>N</I>,<I>N</I>-di-<I>p</I>-methoxyphenylamine-substituted pyrene derivatives have successfully been synthesized and characterized by <SUP>1</SUP>H/<SUP>13</SUP>C NMR spectroscopy, mass spectrometry, and elemental analysis. The optical and electronic structures of the pyrene derivatives were adjusted by controlling the ratio of <I>N</I>,<I>N</I>-di-<I>p</I>-methoxyphenylamine to pyrene, and investigated by UV/vis spectroscopy and cyclic voltammetry. The pyrene derivatives were employed as hole-transporting materials (HTMs) in fabricating mesoporous TiO<SUB>2</SUB>/CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>/HTMs/Au solar cells. The pyrene-based derivative Py-C exhibited a short-circuit current density of 20.2 mA/cm<SUP>2</SUP>, an open-circuit voltage (<I>V</I><SUB>oc</SUB>) of 0.886 V, and a fill factor of 69.4% under an illumination of 1 sun (100 mW/cm<SUP>2</SUP>), resulting in an overall power conversion efficiency of 12.4%. The performance is comparable to that of the well-studied spiro-OMeTAD, even though the <I>V</I><SUB>oc</SUB> is slightly lower. Thus, this newly synthesized pyrene derivative holds promise as a HTM for highly efficient perovskite-based solar cells.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-51/ja410659k/production/images/medium/ja-2013-10659k_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja410659k'>ACS Electronic Supporting Info</A></P>

Fine-tuning the Electronic Structure of Organic Dyes for Dye-Sensitized Solar Cells

Gao, Peng,Tsao, Hoi Nok,Grä,tzel, Michael,Nazeeruddin, Mohammad K. American Chemical Society 2012 Organic letters Vol.14 No.17

<P>A series of metal-free organic dyes exploiting different combinations of (hetero)cyclic linkers (benzene, thiophene, and thiazole) and bridges (4<I>H</I>-cyclopenta[2,1-<I>b</I>:3,4-<I>b′</I>]dithiophene (CPDT) and benzodithiophene (BDT)) as the central π-spacers were synthesized and characterized. Among them, the sensitizer containing the thiophene and CPDT showed the most broad incident photon-to-current conversion efficiency spectra, resulting in a solar energy conversion efficiency (η) of 6.6%.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orlef7/2012/orlef7.2012.14.issue-17/ol301730c/production/images/medium/ol-2012-01730c_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ol301730c'>ACS Electronic Supporting Info</A></P>

Nanowire Perovskite Solar Cell

Im, Jeong-Hyeok,Luo, Jingshan,Franckevic&#x30c,ius, Marius,Pellet, Norman,Gao, Peng,Moehl, Thomas,Zakeeruddin, Shaik Mohammed,Nazeeruddin, Mohammad Khaja,Grä,tzel, Michael,Park, Nam-Gyu American Chemical Society 2015 NANO LETTERS Vol.15 No.3

<P>Organolead iodide perovskite, CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>, was prepared in the form of nanowire by means of a small quantity of aprotic solvent in two-step spin-coating procedure. One-dimensional nanowire perovskite with the mean diameter of 100 nm showed faster carrier separation in the presence of hole transporting layer and higher lateral conductivity than the three-dimensional nanocuboid crystal. Reduction in dimensionality resulted in the hypsochromic shift of both absorption and fluorescence spectra, indicative of more localized exciton states in nanowires. The best performing device employing nanowire CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB> delivered photocurrent density of 19.12 mA/cm<SUP>2</SUP>, voltage of 1.052 V, and fill factor of 0.721, leading to a power conversion efficiency (PCE) of 14.71% at standard AM 1.5G solar illumination. A small <I>I</I>–<I>V</I> hysteresis was observed, where a PCE at forward scan was measured to be 85% of the PCE at reverse scan.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2015/nalefd.2015.15.issue-3/acs.nanolett.5b00046/production/images/medium/nl-2015-00046q_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl5b00046'>ACS Electronic Supporting Info</A></P>

Influence of Donor Groups of Organic D−π–A Dyes on Open-Circuit Voltage in Solid-State Dye-Sensitized Solar Cells

Dualeh, Amalie,De Angelis, Filippo,Fantacci, Simona,Moehl, Thomas,Yi, Chenyi,Kessler, Florian,Baranoff, Etienne,Nazeeruddin, Mohammad K.,Grä,tzel, Michael American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol. No.

<P>In solid-state dye-sensitized solar cells (ssDSCs), the poor pore filling of the mesoporous semiconductor and the short diffusion length of charge carriers in the hole-transport material (HTM) have limited the mesoscopic titania layer to a thickness of 2–3 μm. To increase the amount of light harvested by ssDSCs, organic dyes with high molar extinction coefficients are of great importance and have been the focus of intensive research. Here we investigate ssDSCs using an organic D−π–A dye, coded Y123, and 2,2′,7,7′-tetrakis(<I>N</I>,<I>N</I>-di-<I>p</I>-methoxyphenylamine)-9,9′-spirobifluorene as a hole-transport material, exhibiting 934 mV open-circuit potential and 6.9% efficiency at standard solar conditions (AM1.5G, 100 mW cm<SUP>–2</SUP>), which is a significant improvement compared to the analogue dyes C218, C220, and JK2 (<I>V</I><SUB>oc</SUB> values of 795, 781, and 914 mV, respectively). An upward shift in the conduction band edge was observed from photovoltage transient decay and impedance spectroscopy measurements for devices sensitized with Y123 and JK2 dyes compared to the device using C220 as sensitizer, in agreement with the high photovoltage response of the corresponding ssDSCs. This work highlights the importance of the interaction between the HTM and the dye-sensitized TiO<SUB>2</SUB> surface for the design of ssDSCs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-1/jp209691e/production/images/medium/jp-2011-09691e_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp209691e'>ACS Electronic Supporting Info</A></P>

Cobalt Electrolyte/Dye Interactions in Dye-Sensitized Solar Cells: A Combined Computational and Experimental Study

Mosconi, Edoardo,Yum, Jun-Ho,Kessler, Florian,Go&#x301,mez Garci&#x301,a, Carlos J.,Zuccaccia, Cristiano,Cinti, Antonio,Nazeeruddin, Mohammad K.,Grä,tzel, Michael,De Angelis, Filippo American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.47

<P>We report a combined experimental and computational investigation to understand the nature of the interactions between cobalt redox mediators and TiO<SUB>2</SUB> surfaces sensitized by ruthenium and organic dyes, and their impact on the performance of the corresponding dye-sensitized solar cells (DSSCs). We focus on different ruthenium dyes and fully organic dyes, to understand the dramatic loss of efficiency observed for the prototype Ru(II) N719 dye in conjunction with cobalt electrolytes. Both N719- and Z907-based DSSCs showed an increased lifetime in iodine-based electrolyte compared to the cobalt-based redox shuttle, while the organic D21L6 and D25L6 dyes, endowed with long alkoxy chains, show no significant change in the electron lifetime regardless of employed electrolyte and deliver a high photovoltaic efficiency of 6.5% with a cobalt electrolyte. Ab initio molecular dynamics simulations show the formation of a complex between the cobalt electrolyte and the surface-adsorbed ruthenium dye, which brings the [Co(bpy)<SUB>3</SUB>]<SUP>3+</SUP> species into contact with the TiO<SUB>2</SUB> surface. This translates into a high probability of intercepting TiO<SUB>2</SUB>-injected electrons by the oxidized [Co(bpy)<SUB>3</SUB>]<SUP>3+</SUP> species, lying close to the N719-sensitized TiO<SUB>2</SUB> surface. Investigation of the dye regeneration mechanism by the cobalt electrolyte in the Marcus theory framework led to substantially different reorganization energies for the high-spin (HS) and low-spin (LS) reaction pathways. Our calculated reorganization energies for the LS pathways are in excellent agreement with recent data for a series of cobalt complexes, lending support to the proposed regeneration pathway. Finally, we systematically investigate a series of Co(II)/Co(III) complexes to gauge the impact of ligand substitution and of metal coordination (tris-bidentate vs bis-tridentate) on the HS/LS energy difference and reorganization energies. Our results allow us to trace structure/property relations required for further development of cobalt electrolytes for DSSCs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-47/ja3079016/production/images/medium/ja-2012-079016_0016.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja3079016'>ACS Electronic Supporting Info</A></P>

Perovskite Solar Cells with 12.8% Efficiency by Using Conjugated Quinolizino Acridine Based Hole Transporting Material

Qin, Peng,Paek, Sanghyun,Dar, M. Ibrahim,Pellet, Norman,Ko, Jaejung,Grä,tzel, Michael,Nazeeruddin, Mohammad Khaja American Chemical Society 2014 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.136 No.24

<P>A low band gap quinolizino acridine based molecule was designed and synthesized as new hole transporting material for organic–inorganic hybrid lead halide perovskite solar cells. The functionalized quinolizino acridine compound showed an effective hole mobility in the same range of the state-of-the-art spiro-MeOTAD and an appropriate oxidation potential of 5.23 eV vs the vacuum level. The device based on this new hole transporting material achieved high power conversion efficiency of 12.8% under the illumination of 98.8 mW cm<SUP>–2</SUP>, which was better than the well-known spiro-MeOTAD under the same conditions. Moreover, this molecule could work alone without any additives, thus making it to be a promising candidate for solid-state photovoltaic application.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2014/jacsat.2014.136.issue-24/ja503272q/production/images/medium/ja-2014-03272q_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja503272q'>ACS Electronic Supporting Info</A></P>

Modeling Ruthenium-Dye-Sensitized TiO₂ Surfaces Exposing the (001) or (101) Faces: A First-Principles Investigation

De Angelis, Filippo,Vitillaro, Giuseppe,Kavan, Ladislav,Nazeeruddin, Mohammad. K.,Grä,tzel, Michael American Chemical Society 2012 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.116 No.34

<P>We present a first-principles computational investigation on the adsorption mode and electronic structure of the highly efficient heteroleptic ruthenium dye C101, [NaRu(4,4′-bis(5-hexylthiophene-2-yl)-2,2′-bipyridine)(4-carboxylic acid-4′-carboxylate-2,2′-bipyridine)(NCS)<SUB>2</SUB>], on anatase TiO<SUB>2</SUB> models exposing the (001) and (101) surfaces. The electronic structure of the TiO<SUB>2</SUB> models shows a conduction band energy upshift for the (001)-surface ranging between ∼50 and ∼110 meV compared with the (101) surface, in agreement with previous interfacial impedance and recent spectro-electrochemical data. TDDFT excited-state calculations provided the same optical band gap, within 0.01 eV, for the (001)- and (101) models. Two dominant adsorption modes for C101 dye adsorption on the (001) and (101) surfaces were found, which differ by the binding of the dye carboxylic groups to the TiO<SUB>2</SUB> surfaces (bridged bidentate vs monodentate), leading to sizably different tilting of the anchoring bipyridine plane with respect to the TiO<SUB>2</SUB> surface. The different adsorption mode leads to a smaller dye coverage on the (001) surface, as experimentally found, due to partial contact of the thiophene and alkyl bipyridine substituents with the TiO<SUB>2</SUB> surface. For the energetically favored adsorption modes, we calculate a larger average spatial separation, by 1.3 Å, between the dye-based HOMO and the semiconductor surface in (001) and (101) TiO<SUB>2</SUB> models. In terms of simple nonadiabatic electron-transfer considerations, our model predicts a retardation of the charge recombination kinetics, in agreement with the experimental observations.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-34/jp306186y/production/images/medium/jp-2012-06186y_0008.gif'></P>

Tris(2-(1<i>H</i>-pyrazol-1-yl)pyridine)cobalt(III) as p-Type Dopant for Organic Semiconductors and Its Application in Highly Efficient Solid-State Dye-Sensitized Solar Cells

Burschka, Julian,Dualeh, Amalie,Kessler, Florian,Baranoff, Etienne,Cevey-Ha, Ngoc-Le&#x302,Yi, Chenyi,Nazeeruddin, Mohammad K.,Grä,tzel, Michael American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.45

<P>Chemical doping is an important strategy to alter the charge-transport properties of both molecular and polymeric organic semiconductors that find widespread application in organic electronic devices. We report on the use of a new class of Co(III) complexes as p-type dopants for triarylamine-based hole conductors such as spiro-MeOTAD and their application in solid-state dye-sensitized solar cells (ssDSCs). We show that the proposed compounds fulfill the requirements for this application and that the discussed strategy is promising for tuning the conductivity of spiro-MeOTAD in ssDSCs, without having to rely on the commonly employed photo-doping. By using a recently developed high molar extinction coefficient organic D-π-A sensitizer and p-doped spiro-MeOTAD as hole conductor, we achieved a record power conversion efficiency of 7.2%, measured under standard solar conditions (AM1.5G, 100 mW cm<SUP>–2</SUP>). We expect these promising new dopants to find widespread applications in organic electronics in general and photovoltaics in particular.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2011/jacsat.2011.133.issue-45/ja207367t/production/images/medium/ja-2011-07367t_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja207367t'>ACS Electronic Supporting Info</A></P>

Thermal Behavior of Methylammonium Lead-Trihalide Perovskite Photovoltaic Light Harvesters

Dualeh, Amalie,Gao, Peng,Seok, Sang Il,Nazeeruddin, Mohammad Khaja,Grä,tzel, Michael American Chemical Society 2014 Chemistry of materials Vol.26 No.21

<P>Recently organic–inorganic hybrid perovskites have attracted attention as light harvesting materials in mesoscopic cells. While a considerable number of deposition and formation methods have been reported for the perovskite crystalline material, most involve an annealing step. As such, the thermal behavior of this material and its individual components is of crucial interest. Here, we examine the thermal properties of the CH<SUB>3</SUB>NH<SUB>3</SUB>PbX<SUB>3</SUB> (X = I or Cl) perovskite using thermogravimetric analysis. The role of the precursors is exposed, and the effect of the formation of excess organic species is investigated. The sublimation behavior of the organic component is intensively scrutinized. Furthermore, differential scanning calorimetry is employed to probe the crystal phase structure, revealing subtle differences depending on the deposition method.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2014/cmatex.2014.26.issue-21/cm502468k/production/images/medium/cm-2014-02468k_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm502468k'>ACS Electronic Supporting Info</A></P>

Design and Development of Functionalized Cyclometalated Ruthenium Chromophores for Light-Harvesting Applications

Robson, Kiyoshi C. D.,Koivisto, Bryan D.,Yella, Aswani,Sporinova, Barbora,Nazeeruddin, Mohammad K.,Baumgartner, Thomas,Grä,tzel, Michael,Berlinguette, Curtis P. American Chemical Society 2011 Inorganic Chemistry Vol.50 No.12

<P>The syntheses and the electrochemical spectroscopic properties of a suite of asymmetrical <I>bis</I>tridentate cyclometalated Ru(II) complexes bearing terminal triphenylamine (TPA) substituents are reported. These complexes, which contain structural design elements common to both inorganic and organic dyes that exhibit superior power conversion efficiencies in the dye-sensitized solar cell (DSSC), are broadly formulated as [Ru<SUP>II</SUP>(L-2,5′-thiophene-TPA-R<SUB>1</SUB>)(L-R<SUB>2</SUB>)]<SUP>+</SUP> [L = tridentate chelating ligand (e.g., 2,2′:6′,2′′-terpyridine (tpy); deprotonated forms of 1,3-di(pyridin-2-yl)benzene (Hdpb) or 6-phenyl-2,2′-bipyridine (Hpbpy)); R<SUB>1</SUB> = −H, −Me, −OMe; R<SUB>2</SUB> = −H, −CO<SUB>2</SUB>Me, −CO<SUB>2</SUB>H]. The following structural attributes were systematically modified for the series: (i) electron-donating character of the terminal substituents (e.g., R<SUB>1</SUB> = −H, −Me, −OMe) placed <I>para</I> to the amine of the “L-2,5′-thiophene-TPA-R<SUB>1</SUB>” ligand framework; (ii) electron-withdrawing character of the tridentate chelate distal to the TPA-substituted ligand (e.g., R<SUB>2</SUB> = −H, −CO<SUB>2</SUB>Me, −CO<SUB>2</SUB>H); and (iii) position of the organometallic bond about the Ru(II) center. UV–vis spectra reveal intense and broad absorption bands arising from a collection of metal-to-ligand charge-transfer (MLCT) and TPA-based intraligand charge-transfer (ILCT) transitions that, in certain cases, extend beyond 800 nm. Electrochemical data indicate that the oxidative behavior of the TPA and metal chelate units can be independently modulated except in cases where the anionic phenyl ring is in direct conjugation with the TPA unit. In most cases, the anionic character of the cyclometalating ligands renders a metal-based oxidation event prior to the oxidation of the TPA unit. This situation can, however, be reversed with an appropriately positioned Ru–C bond and electron-rich R<SUB>1</SUB> group. This finding is important in that this arrangement confines the highest occupied molecular orbital (HOMO) to the TPA unit rather than the metal, which is optimal for sensitizing TiO<SUB>2</SUB>; indeed, a remarkably high power conversion efficiency (η) in the DSSC (i.e., 8.02%) is measured for the TPA-substituted pbpy<SUP>–</SUP> chelate where R<SUB>1</SUB> = −OMe. These results provide a comprehensive strategy for improving the performance of <I>bis</I>tridentate Ru sensitizers devoid of NCS<SUP>–</SUP> groups for the DSSC.</P><P>A series of bichromic cyclometalated <I>bis</I>tridentate Ru(II) complexes containing a triphenylamine-based donor unit produce broad, intense absorbance profiles. The ability to modulate the redox behavior of each of the chromophore units independently was exploited to converge on a high-performance class of dyestuff devoid of NCS<SUP>−</SUP> ligands.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/inocaj/2011/inocaj.2011.50.issue-12/ic200011m/production/images/medium/ic-2011-00011m_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ic200011m'>ACS Electronic Supporting Info</A></P>