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Papers by Alejandra Soriano

MRS Proceedings, 2013

ABSTRACT We present normal and inverted solution processed bi-layer solar cells using cationic cy... more ABSTRACT We present normal and inverted solution processed bi-layer solar cells using cationic cyanine dyes as the electron donor and a fullerene as the electron acceptor. The cells exhibit high open circuit voltages up to 1 volt showing the optimal alignment of donor and acceptor energy levels. We demonstrate the large effect that cyanine dye counter ions can have on the energetics of the solar cells and how the S-shaped current density vs. voltage (J-V) curves can be avoided.

Advanced Energy Materials, 2012

ABSTRACT Simple bilayer solar cells, using commercially available cationic cyanine dyes as donors... more ABSTRACT Simple bilayer solar cells, using commercially available cationic cyanine dyes as donors and evaporated C60 layer as an acceptor are prepared. Cyanine dyes with absorption maxima of 578, 615 and 697 nm having either perchlorate or hexafluorophosphate counter-ions are evaluated. The perchlorate dye leads to cells with S-shape current-voltage curves; only the dyes with the hexafluorophosphate counter-ions lead to efficient solar cells. When the wide bandgap dyes are employed, S-shape current-voltage curves are obtained when the conductive polymer PEDOT:PSS is used as hole transport layer. Substitution of PEDOT:PSS with MoO3 leads to cells with more rectangular current–voltage curves and high fill factors. Additionally, the cells using the MoO3 layer for hole extraction lead to high open circuit voltages of 0.9 V. In the case that a low bandgap hexafluorophosphate dye is used with the HOMO above that of the PEDOT:PSS the cell performance is independent on the type of hole transport layer employed. Using this approach, bilayer solar cells are obtained with power efficiencies ranging from 1.8 to 2.9% depending on the particular dye employed. These are impressive numbers for bilayer solar cell that are partially solution processed in ambient conditions.

On this paper the first Building Integrated Hybrid Photovoltaic (BIHPV) cell obtained on a commer... more On this paper the first Building Integrated Hybrid Photovoltaic (BIHPV) cell obtained on a commercial tile is presented. The experimental techniques used allow a future low cost development of these cells for its massive use on facades for buildings. The basic concept ...

Advanced Energy Materials, 2014

Chemical Physics Letters - CHEM PHYS LETT, 2008

Capacitance analysis of P3HT:PCBM bulk heterojunction solar cells, in dark and under illumination... more Capacitance analysis of P3HT:PCBM bulk heterojunction solar cells, in dark and under illumination, shows a linear Mott–Schottky characteristic at moderate reverse bias, indicating p-doping of the organic blend. The flatband potential under illumination is displaced negatively about 0.6 V with respect to dark conditions. A basic photovoltaic model is developed to explain this, in terms of electron transfer via surface states at the metal/organic interface. Surface states with a slow exchange kinetics, become charged under illumination, unpinning the band and decreasing the depletion layer at the electron extraction contact. This becomes a major factor limiting the performance of bulk heterojunction solar cells.Linear plots of C−2 vs. voltage in P3HT-PCBM organic solar cells, shitf under illumination, indicating the charging of a surface state.

Journal of Porphyrins and Phthalocyanines, 2013

ABSTRACT A new tricationic subphthalocyanine was synthesized and employed as light-harvesting and... more ABSTRACT A new tricationic subphthalocyanine was synthesized and employed as light-harvesting and donor material in an ionic solid state organic photovoltaic cell. The incorporation of ionic dyes in organic photovoltaics aims to take advantage of ionic movement in order to enhance the charge transport properties of these materials. In this preliminary study, we report the results obtained in the fabrication of a partially solution-processed device with a cationic dye, where an effiency of 0.5% was reached

Energy & Environmental Science, 2014

Thin-film photovoltaics play an important role in the quest for clean renewable energy. Recently,... more Thin-film photovoltaics play an important role in the quest for clean renewable energy. Recently, methylammonium lead halide perovskites were identified as promising absorbers for solar cells 1 . In the three years since, the performance of perovskite-based solar cells has improved rapidly to reach efficiencies as high as 15% 1-10 . To date, all high-efficiency perovskite solar cells reported make use of a (mesoscopic) metal oxide, such as Al 2 O 3 , TiO 2 or ZrO 2 , which requires a high-temperature sintering process. Here, we show that methylammonium lead iodide perovskite layers, when sandwiched between two thin organic charge-transporting layers, also lead to solar cells with high power-conversion efficiencies (12%). To ensure a high purity, the perovskite layers were prepared by sublimation in a high-vacuum chamber. This simple planar device structure and the room-temperature deposition processes are suitable for many conducting substrates, including plastic and textiles.

Chemical Physics Letters, 2008

Capacitance analysis of P3HT:PCBM bulk heterojunction solar cells, in dark and under illumination... more Capacitance analysis of P3HT:PCBM bulk heterojunction solar cells, in dark and under illumination, shows a linear Mott-Schottky characteristic at moderate reverse bias, indicating p-doping of the organic blend. The flatband potential under illumination is displaced negatively about 0.6 V with respect to dark conditions. A basic photovoltaic model is developed to explain this, in terms of electron transfer via surface states at the metal/organic interface. Surface states with a slow exchange kinetics, become charged under illumination, unpinning the band and decreasing the depletion layer at the electron extraction contact. This becomes a major factor limiting the performance of bulk heterojunction solar cells.

MRS Proceedings, 2013

ABSTRACT We present normal and inverted solution processed bi-layer solar cells using cationic cy... more ABSTRACT We present normal and inverted solution processed bi-layer solar cells using cationic cyanine dyes as the electron donor and a fullerene as the electron acceptor. The cells exhibit high open circuit voltages up to 1 volt showing the optimal alignment of donor and acceptor energy levels. We demonstrate the large effect that cyanine dye counter ions can have on the energetics of the solar cells and how the S-shaped current density vs. voltage (J-V) curves can be avoided.

Advanced Energy Materials, 2012

ABSTRACT Simple bilayer solar cells, using commercially available cationic cyanine dyes as donors... more ABSTRACT Simple bilayer solar cells, using commercially available cationic cyanine dyes as donors and evaporated C60 layer as an acceptor are prepared. Cyanine dyes with absorption maxima of 578, 615 and 697 nm having either perchlorate or hexafluorophosphate counter-ions are evaluated. The perchlorate dye leads to cells with S-shape current-voltage curves; only the dyes with the hexafluorophosphate counter-ions lead to efficient solar cells. When the wide bandgap dyes are employed, S-shape current-voltage curves are obtained when the conductive polymer PEDOT:PSS is used as hole transport layer. Substitution of PEDOT:PSS with MoO3 leads to cells with more rectangular current–voltage curves and high fill factors. Additionally, the cells using the MoO3 layer for hole extraction lead to high open circuit voltages of 0.9 V. In the case that a low bandgap hexafluorophosphate dye is used with the HOMO above that of the PEDOT:PSS the cell performance is independent on the type of hole transport layer employed. Using this approach, bilayer solar cells are obtained with power efficiencies ranging from 1.8 to 2.9% depending on the particular dye employed. These are impressive numbers for bilayer solar cell that are partially solution processed in ambient conditions.

On this paper the first Building Integrated Hybrid Photovoltaic (BIHPV) cell obtained on a commer... more On this paper the first Building Integrated Hybrid Photovoltaic (BIHPV) cell obtained on a commercial tile is presented. The experimental techniques used allow a future low cost development of these cells for its massive use on facades for buildings. The basic concept ...

Advanced Energy Materials, 2014

Chemical Physics Letters - CHEM PHYS LETT, 2008

Capacitance analysis of P3HT:PCBM bulk heterojunction solar cells, in dark and under illumination... more Capacitance analysis of P3HT:PCBM bulk heterojunction solar cells, in dark and under illumination, shows a linear Mott–Schottky characteristic at moderate reverse bias, indicating p-doping of the organic blend. The flatband potential under illumination is displaced negatively about 0.6 V with respect to dark conditions. A basic photovoltaic model is developed to explain this, in terms of electron transfer via surface states at the metal/organic interface. Surface states with a slow exchange kinetics, become charged under illumination, unpinning the band and decreasing the depletion layer at the electron extraction contact. This becomes a major factor limiting the performance of bulk heterojunction solar cells.Linear plots of C−2 vs. voltage in P3HT-PCBM organic solar cells, shitf under illumination, indicating the charging of a surface state.

Journal of Porphyrins and Phthalocyanines, 2013

ABSTRACT A new tricationic subphthalocyanine was synthesized and employed as light-harvesting and... more ABSTRACT A new tricationic subphthalocyanine was synthesized and employed as light-harvesting and donor material in an ionic solid state organic photovoltaic cell. The incorporation of ionic dyes in organic photovoltaics aims to take advantage of ionic movement in order to enhance the charge transport properties of these materials. In this preliminary study, we report the results obtained in the fabrication of a partially solution-processed device with a cationic dye, where an effiency of 0.5% was reached

Energy & Environmental Science, 2014

Thin-film photovoltaics play an important role in the quest for clean renewable energy. Recently,... more Thin-film photovoltaics play an important role in the quest for clean renewable energy. Recently, methylammonium lead halide perovskites were identified as promising absorbers for solar cells 1 . In the three years since, the performance of perovskite-based solar cells has improved rapidly to reach efficiencies as high as 15% 1-10 . To date, all high-efficiency perovskite solar cells reported make use of a (mesoscopic) metal oxide, such as Al 2 O 3 , TiO 2 or ZrO 2 , which requires a high-temperature sintering process. Here, we show that methylammonium lead iodide perovskite layers, when sandwiched between two thin organic charge-transporting layers, also lead to solar cells with high power-conversion efficiencies (12%). To ensure a high purity, the perovskite layers were prepared by sublimation in a high-vacuum chamber. This simple planar device structure and the room-temperature deposition processes are suitable for many conducting substrates, including plastic and textiles.

Chemical Physics Letters, 2008

Capacitance analysis of P3HT:PCBM bulk heterojunction solar cells, in dark and under illumination... more Capacitance analysis of P3HT:PCBM bulk heterojunction solar cells, in dark and under illumination, shows a linear Mott-Schottky characteristic at moderate reverse bias, indicating p-doping of the organic blend. The flatband potential under illumination is displaced negatively about 0.6 V with respect to dark conditions. A basic photovoltaic model is developed to explain this, in terms of electron transfer via surface states at the metal/organic interface. Surface states with a slow exchange kinetics, become charged under illumination, unpinning the band and decreasing the depletion layer at the electron extraction contact. This becomes a major factor limiting the performance of bulk heterojunction solar cells.