Kieran C. Molloy

Nanostructured Hybrid Polymer−Inorganic Solar Cell Active Layers Formed by Controllable in Situ Growth of Semiconducting Sulfide Networks

Nanostructured composites of inorganic and organic materials are attracting extensive interest for electronic and optoelectronic device applications. In this paper, we introduce a general method for the fabrication of metal sulfide nanoparticle/polymer films employing a low-cost and low temperature route compatible with large-scale device manufacturing. Our approach is based upon the controlled in situ thermal decomposition of a solution processable metal xanthate precursor complex in a semiconducting polymer film. To demonstrate the versatility of our method, we fabricate a CdS/P3HT nanocomposite film and show that the metal sulfide network inside the polymer film assists in the absorption of visible light and enables the achievement of high yields of charge photogeneration at the CdS/P3HT heterojunction. Photovoltaic devices based upon such nanocomposite films show solar light to electrical energy conversion efficiencies of 0.7% under full AM1.5 illumination and 1.2% under 10% incident power, demonstrating the potential of such nanocomposite films for low-cost photovoltaic devices.

Direct Growth of Metal Sulfide Nanoparticle Networks in Solid‐State Polymer Films for Hybrid Inorganic–Organic Solar Cells

Hybrid metal sulfide/polymer solar cell active layers are fabricated employing an approach based upon the in-situ thermal decomposition of a single source metal xanthate precursor in a semiconducting polymer film. The nanomorphology of the film, the charge photogeneration yield at the donor-acceptor heterojunction and device performance are shown to be dependent upon the annealing temperature. Photovoltaic devices based upon such layers are shown to exhibit power conversion efficiencies of 2.2% under AM1.5 solar illumination thus demonstrating the potential of such nanocomposite films for photovoltaic device applications.

Synthesis, structure and light-harvesting properties of some new transition-metal dithiocarbamates involving ferrocene.

Nine new transition-metal dithiocarbamates involving ferrocene (Fc), namely, [M(FcCH(2)Bzdtc)(2)] (M=Ni(II) (1), Cu(II) (2), Cd(II) (3), Hg(II) (4), Pd(II) (5), Pt(II) (6) and Pb(II) (7); Bzdtc=N-benzyl dithiocarbamate) and [M(FcCH(2)Bzdtc)(3)] (M=Co(II) (8) and UO(2) (VI) (9)), have been synthesised and characterised by micro analyses, IR spectroscopy, (1)H and (13)C NMR spectroscopy, and in three cases by single-crystal X-ray analysis. The peak broadening in the (1)H spectrum of the copper complex indicates the paramagnetic behaviour of this compound. A square-planar geometry around the nickel and copper complexes and distorted linear geometry around the mercury complex have been found. The latter geometry is attributed to the bulkiness of the methylferrocenyl and benzyl groups. The observed single quasi-reversible cyclic voltammograms for complexes 2, 8 and 9 indicate the stabilisation of a metal centre other than Fe in their characteristic oxidation state. These complexes have been used as a photosensitiser in dye-sensitised solar cells.

Organotin unsymmetric dithiocarbamates: synthesis, formation and characterisation of tin(II) sulfide films by atmospheric pressure chemical vapour deposition

A series of tin unsymmetric dithiocarbamate complexes have been made from metathesis reaction of [CH3(C4H9)NSC2]Li and RnSnCl4-n; [RnSn(S2CN(C4H9)CH3)(4-n)] [n = 3, R = Me (1), Bu (2), Ph (3); n = 2, R = Me (4), Bu (5), Ph (6); n = 1, R = Me (7), Bu (8), Ph (9)]. The complexes were characterised by microanalysis, C-13, H-1 and Sn-119 NMR, Mossbauer and, in the case of 3, by X-ray diffraction, which revealed one short Sn-S [2.4631(9) Angstrom] and one long Sn-S interaction [3.084(l) Angstrom] indicative of a weakly chelating dithiocarbamate ligand. Atmospheric pressure chemical vapour deposition using I and 8 with H2S at 350-550 degreesC produced SnS and Sn2S3 films on glass substrates. The tin sulfides were analysed by Raman, EDAX, SEM and band gap measurements. Growth rates were of the order of 150 nm min(-1)

Influence of crystallinity and energetics on charge separation in polymer-inorganic nanocomposite films for solar cells.

The dissociation of photogenerated excitons and the subsequent spatial separation of the charges are of crucial importance to the design of efficient donor-acceptor heterojunction solar cells. While huge progress has been made in understanding charge generation at all-organic junctions, the process in hybrid organic:inorganic systems has barely been addressed. Here, we explore the influence of energetic driving force and local crystallinity on the efficiency of charge pair generation at hybrid organic:inorganic semiconductor heterojunctions. We use x-ray diffraction, photoluminescence quenching, transient absorption spectroscopy, photovoltaic device and electroluminescence measurements to demonstrate that the dissociation of photogenerated polaron pairs at hybrid heterojunctions is assisted by the presence of crystalline electron acceptor domains. We propose that such domains encourage delocalization of the geminate pair state. The present findings suggest that the requirement for a large driving energy for charge separation is relaxed when a more crystalline electron acceptor is used.

Deposition of tin sulfide thin films from tin(IV) thiolate precursors

AACVD (aerosol-assisted chemical vapour deposition) using (PhS)(4)Sn as precursor leads to the deposition of Sn3O4 in the absence of H2S and tin sulfides when H2S is used as co-reactant. At 450 degreesC the film deposited consists of mainly SnS2 while at 500 degreesC SnS is the dominant component. The mechanism of decomposition of (PhS)(4)Sn is discussed and the structure of the precursor presented.

Aerosol-assisted chemical vapour deposition (AACVD) of silver films from triorganophosphine adducts of silver carboxylates, including the structure of [Ag(O2CC3F7)(PPh3)(2)]

Abstract Silver carboxylates [Ag(O 2 CR): R=Me, t Bu, 2,4,6-Me 3 C 6 H 2 ], fluorocarboxlyates [Ag(O 2 CR f ): R f =C 3 F 7 , C 6 F 13 , C 7 F 15 ] and their phosphine adducts [Ag(O 2 CR)· n PR 3 ′: R=Me, t Bu, 2,4,6-Me 3 C 6 H 2 , R′=Me, Ph, n =2; R=Me, R′=Me, n =3; Ag(O 2 CR f ).2PPh 3 , R f =C 3 F 7 , C 6 F 13 , C 7 F 15 ] have been synthesised, characterised spectroscopically and used as precursors in the aerosol-assisted chemical vapour deposition of silver films. All the phosphine adducts produced films, though in general PMe 3 adducts, proved more successful than PPh 3 analogues. The fluoro-carboxylates and their PPh 3 adducts all generated silver films, though the growth rate for the adducts was lower. All these latter films showed carbon impurities while fluorine was also evident in most cases. The X-ray structure of AgO 2 CC 3 F 7 ·2PPh 3 is also reported.

Aerosol-assisted chemical vapour deposition (AACVD) of silver films from triphenylphosphine adducts of silver β-diketonates and β-diketoiminates, including the structure of [Ag(hfac)(PPh3)]

Triphenylphosphine adducts of silver β-diketonates [AgL(PPh 3 )] (L=acac, dpm, tfac, hfac, fod) and β-ketoiminates (L=hfacNhex, hfacNchex) have been synthesised and evaluated as precursors for the deposition of silver films using aerosol-assisted chemical vapour deposition methodology. The 1:1 stoichiometry of the adducts has been established by 31 P and 109 Ag NMR and a crystal structure of [Ag(hfac)(PPh 3 )]. The best films were obtained from the two β-ketoiminates, particularly L=hfacNhex. While [AgL(PPh 3 )] (L=acac, dpm) gave almost no deposition, the complex with L=tfac gave a film comparable with the two β-ketoiminates while other films showed poor reflectivity (L=hfac, fod).

Deposition of tin sulfide thin films from novel, volatile (fluoroalkythiolato)tin(IV) precursors

Novel, volatile (fluoroalkylthiolato)tin(IV) precursors have been synthesised and (CF3CH2S)4Sn used to deposit tin sulfide films under APCVD (atmospheric pressure chemical vapour deposition) conditions. H2S is, however, required as co-reactant. Films deposited at 300–400 °C are composed of sulfur-deficient SnS2, films deposited at 450 and 500 °C comprise the sesquisulfide, Sn2S3, and the films deposited at 550 or 600 °C are sulfur-deficient SnS. The structure of [CF3(CF2)5CH2CH2S]4Sn is also reported.

Organocadmium aminoalcoholates: Synthesis, structure, and materials chemistry

The novel methylcadmium aminoalkoxides MeCd(dmae) (Hdmae = dimethylaminoethanol), MeCd(bdmap) [Hbdmap = 1,3- bis-(dimethylamino)-propan-2-ol], and MeCd(tdmap) [tdmap = 1,3- bis(dimethylamino)-2-(dimethylaminomethyl)-propan-2-ol] have been synthesized and structurally characterized. MeCd(dmae) (1) forms a tetrameric heterocubane with a Cd4O4 core, while MeCd(bdmap) (2) is trimeric and MeCd(tdmap) (3) is a dimer. Only in the case of MeCd(dmae) are all the ligand donors fully utilized. In solution, MeCd(tdmap) undergoes a Schlenk equilibrium, with Me2Cd and Cd(tdmap)2 evident at 218 K. The structure and solution-state chemistry of Cd(tdmap)2 (5) have been independently studied and, in the solid-state, found to exist as a dimer whose coordination number at cadmium (CN = 6) is greater than in the organocadmium complexes (CN = 4, 5). MeCd(tdmap) has been used as a single-source precursor for CdO films by LPCVD with a glass substrate temperature of only 140 degrees C. Evidence is also presented for the formation of a heterometallic precursor, [(MeZn)(MeCd)(tdmap)2] (6), which has been used to deposit films of CdO mixed with ZnO by LPCVD at 140 degrees C. The structure of Me4Cd4(tdmap)2Cl2 (4), obtained serendipitously, is also included. Crystal data: 1, C20H52Cd4N4O4, FW 862.26, triclinic, P1, a = 11.47560(10), b = 13.55400(10), c = 21.5966(2) A, alpha = 99.7869(4), beta = 90.7476(4), gamma = 98.7823(4) degrees, V = 3268.82(5) A(3), Z = 4; 2, C27H67Cd3N6O3, FW 861.07, triclinic, P1, a = 11.4148(2), b =13.1886(2), c = 14.3139(3) A, alpha = 102.1962(10), beta = 108.3064(10), gamma = 100.8446(10) degrees, V = 1923.09(6) A(3), Z = 4; 3, C22H54Cd2N6O2, FW 659.51, monoclinic, P2(1)/n, a = 10.2912(1), b = 13.46930(1), c = 11.79130(1) A, beta = 112.8051(1) degrees, V = 1506.59(2) A(3), Z = 2; 4, C24H60Cd4Cl2N6O2, FW 985.28, monoclinic, P2(1)/c, a = 10.89780(10), b = 20.3529(2), c = 16.5317(2) A, beta = 94.8550(10) degrees, V = 3653.61(7) A(3), Z = 4; 5, C40H96Cd2N12O4, FW 1034.09, orthorhombic, P2(1)cn, a = 12.33290(10), b = 14.25060(10), c = 29.9003(2) A, V = 5255.01(7) A(3), Z = 4.