Phthalocyanine organic solar cells: Indium/x-metal free phthalocyanine Schottky barriers

Abstract

A thin organic film of polycrystalline particles of x-metal free phthalocyanine (x-H2Pc) dispersed in a polymer binder, when sandwiched between tin oxide (NESA) and indium electrodes, is shown to exhibit a strong photovoltaic effect. The photovoltaic and rectification properties of In/x-H2Pc/NESA sandwich cells are reported. From the photovoltaic action spectra, the active region responsible for electric power generation was found to be confined to the metal/semiconductor interface. A Schottky barrier width of 300 Å was determined, which allows the capture of 30% of solar irradiance. An electron trap density of 3×1017/cm3 and a Schottky barrier built-in potential of 0.63 V are estimated from C-V measurements. At low voltage, the dark current in the forward direction varies exponentially with voltage: from this dependence values of 2×10−9 A/cm2 and 1.3–2.6 for the saturation current J0 and diode quality factor n are determined. At higher voltage, a super quadratic dependence of forward current on voltage indicated that current conduction is limited by an exponentially decreasing distribution of traps. At peak solar power (135 mW/cm2), a power conversion efficiency (η′) of 1.2% to transmitted light has been obtained. The transmittance of the indium electrode approached 2%. The devices exhibit open circuit voltages Voc of 0.45 V and short-circuit currents of 0.2 mA/cm2 at Air Mass Zero (AMO) sunlight. Therefore, the engineering efficiency of our device approached 0.03%. The monochromatic quantum efficiency of free-carrier generation approached 75% at low light level; this diminished to 30% at solar intensities, characteristic of a cell with large series resistance. The effect of pigment loading, cell thickness, light intensity, binder material, dye sensitization, and the nature of barrier electrode has been studied and optimized.

Solvent impact on the planarity and aromaticity of free and monohydrated zinc phthalocyanine: a theoretical study

“…Since then on, numerous complexes of transition metal ions with phthalocyanine molecule (Pc), which contains eight nitrogen atoms, four pyrrole subunits joined with four azomethine bridges, and four benzene rings, have been commonly used as pigments and dyes [3][4][5][6][7]. Apart from basic research, various phthalocyanine derivatives, including MPcs, have been used as semiconductors, optoelectronic materials, catalysts, and photosensibilizers in photodynamic therapy (PDT) against cancer and as contrast agents in medical diagnostics in magnetic resonance imaging [3][4][5][6][7][8][9][10][11][12][13][14][15]. In regard to the latter applications, solubility in water is an important factor for the biologically active compounds [16].…”

Photoélectrochimie des phtalocyanines sans métal, de cuivre et de fer

“…Ces dopants agissent cornme pikges h Clectrons, entrainant la creation d'un plus grand nombre de trous mobiles. ~t a n t donnC que les phtalocyanines absorbent fortement dans la region visible du spectre solaire, avec une bande interdite de l'ordre de 1,8-2,l eV (3), il a CtC suggere de les utiliser dans des cellules photovoltai'ques (9)(10)(11)(12)(13)(14)(15)(16). Bien que le rendement de conversion de 1'Cnergie solaire en Cnergie Clectrique soit trks faible (< 1 %), a cause principalement du faible rendernent quantique, certaines phtalocyanines (H,Pc, CuPc, NiPc, MgPc) ont manifest6 des activitCs intkressantes.…”

CdS/chloroaluminum phthalocyanine heterojunctions: effect of CdS preparation method on the efficiency of photovoltaic cells

“…Since most of the Pcs investigated are characterized by a p-type behavior, the photovoltaic effects were first observed with Schottky barriers obtained by contacting the dyes with metals like A1 or In (1)(2)(3)(4). Besides showing stability problems, these metallic electrodes also absorb a large fraction of the light in the Q band absorption region of the organic semiconductor.…”