Factors affecting the photovoltaic behavior of inverted polymer solar cells using various indium tin oxide electrodes modified by amines with simple chemical structures

Kusumi, Takuji; Yamaguchi, Takahiro; Taima, Tetsuya; Takahashi, Kohshin

doi:10.1016/j.tsf.2015.08.025

Cited by 7 publications

(18 citation statements)

References 39 publications

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“…The I p was reduced more effectively for a larger number of amino groups in the amine molecule, in the order of piperazine < NAP < BAP. 15 However, the I p of the modified ITOs suddenly increased when BAP and NAP solutions with concentrations greater than 1 and 2 M, respectively, were spin-cast. This result suggests that when a large excess of piperazine derivatives was deposited on ITO, the amines acted as an insulator, which interfered with photoelectron emission from the ITO.…”

Section: Resultsmentioning

confidence: 98%

Mechanism of Light-Soaking Effect in Inverted Polymer Solar Cells with Open-Circuit Voltage Increase

Kusumi¹,

Fujimori²,

Minami³

et al. 2017

ACS Omega

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In this study, we present novel insights into the light-soaking effect of inverted polymer solar cells (PSCs), where the open-circuit voltage ( V oc ) of the cells improves over time under light irradiation. The effect was investigated by electron spin resonance (ESR) studies of bare indium tin oxide (ITO) and piperazine derivative-modified ITO/regioregular poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C 61 butyric acid methyl ester (PCBM) substrates. These results were combined with alternating current impedance spectroscopy (IS) measurements of inverted PSCs based on the above substrates. In ESR experiments with the substrates under white light irradiation, with a UV light component, many P3HT •+ radical cations were observed in the bare-ITO/P3HT:PCBM substrate. The number of radical cations was considerably suppressed in the ITO/P3HT:PCBM substrates with ITO modified by piperazine derivatives. This is because adsorbed oxygen molecules on the ITO acted as acceptor dopants for photoexcited P3HT, and the amount of adsorbed oxygen was decreased by modifying the ITO with piperazine derivatives. In IS measurements of the inverted PSCs under white light irradiation, a decrease in the electric capacitance (CPE2) of an electric double layer formed at the ITO/P3HT:PCBM interface was observed. A strong correlation was observed between the decrease of CPE2 and the increase of V oc . From these results, the light-soaking behavior was attributed to the removal of an electron injection barrier formed between ITO and PCBM, under white light irradiation.

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Section: Resultsmentioning

confidence: 98%

Mechanism of Light-Soaking Effect in Inverted Polymer Solar Cells with Open-Circuit Voltage Increase

Kusumi¹,

Fujimori²,

Minami³

et al. 2017

ACS Omega

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“…Previously, we have identified the amine molecules were adsorbed chemically on the ITO, but not physically, because we observed existence of protonated amines on ITO by XPS measurements. 19 Thus, this decrease in the I P of the PEIE-modified ITO also suggests that amino-groups in PEIE chemically bond to hydroxyl groups of ITO by an acid-base reaction. Whereas, it is also known that a zwitter ion such as TPPBS can reduce the work function of ITO by adsorbing on the ITO surface because of the dipole moment originated from positive and negative charges in the structure.…”

Section: Resultsmentioning

confidence: 91%

“…This corresponds with the previous results which the V oc of the inverted polymer solar cells was improved by a decrease in the I P caused due to adsorption of various amines on ITO. 19 In the case of air-produced polymer solar cells, desorption of the chemical-adsorbed oxygen on ITO by UV light irradiation leads to disappear the energy mismatch, that is, the desorption strongly induces the light-soaking effect of V oc -dependent type. 23 On the other hand, when we repeated the I-V measurements for the TPPBS-modified ITO cells under UV-cut light, we found that the light-soaking behavior was suppressed and an increase in the V oc was observed.…”

Section: ¹2mentioning

confidence: 99%

“…However, such the increasing process is poorly understood, although several mechanisms have been suggested. [11][12][13][14][15] We previously have found that there are two kinds of light soaking effects such as a short-circuit current density (J sc ) dependent type [16][17][18] and an open-circuit voltage (V oc ) dependent type 19 as shown in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

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An Increase in Open-circuit Photo-voltage of Inverted Polymer Solar Cells by Pre-treatment Applying Forward Bias Under UV-cut Light Irradiation

Minami¹,

Kusumi²,

Yamaguchi³

et al. 2017

Electrochemistry

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We present a novel insight on the light-soaking effect, in which the open-circuit voltage (V oc ) of inverted polymer solar cells improves with increase in light irradiation time. We previously have found that there are two kinds of the light soaking effects such as a short-circuit current density dependent type and a V oc dependent type. The expression of these effects needed to irradiate the light containing UV component. However, for 4-(triphenylphosphonio)butane-1-sulfonate (TPPBS)-modified indium tin oxide (ITO)/poly(3-hexylthiophene-2,5-diyl) (P3HT): [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM)/poly(3,4-ethylenedioxylenethiophene):poly(4-styrene sulfonic acid) (PEDOT:PSS)/Au inverted cell, we first observed an increase in the V oc by irradiating white light not containing UV component. After pre-treatment by applying forward bias under UV-cut light, the V oc was improved even when the performance was evaluated by irradiating UV-cut light, that is, the V oc values of 0.36, 0.42, 0.46 and 0.54 V were obtained by holding at forward voltages of 0, 0.3, 0.6, and 1.0 V, respectively. We discussed about this pretreatment effect from the viewpoint of desorption of oxygen molecules adsorbing on ITO.

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“…Reducing the ITO work function for efficient electron collection was achieved using metal oxides (TiO x , ZnO), − alkali metal salts (e.g., Cs 2 CO 3 ), and organic materials, such as fullerene derivatives, − conjugated polymers, , zwitterions, self-assembled monolayers of organic conjugated molecules − or peptides, amines, , ethylene glycols, and poly(4-vinylpyridine) . However, all these modifiers have certain disadvantages related to the complexity of their processing, insufficient electronic performance, or poor stability.…”

Section: Introductionmentioning

confidence: 99%

ITO Modification for Efficient Inverted Organic Solar Cells

et al. 2017

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We demonstrate a facile approach to designing transparent electron-collecting electrodes by depositing thin layers of medium and low work function metals on top of transparent conductive metal oxides (TCOs) such as ITO and FTO. The modified electrodes were fairly stable for months under ambient conditions and maintained their electrical characteristics. XPS spectroscopy data strongly suggested integration of the deposited metal in the TCO structure resulting in additional doping of the conducting oxide at the interface. Kelvin probe microscopy measurements revealed a significant decrease in the ITO work function after modification. Organic solar cells based on three different conjugated polymers have demonstrated state of the art performances in inverted device geometry using Mg- or Yb-modified ITO as electron collecting electrode. The simplicity of the proposed approach and the excellent ambient stability of the modified ITO electrodes allows one to expect their wide utilization in research laboratories and electronic industry.

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Factors affecting the photovoltaic behavior of inverted polymer solar cells using various indium tin oxide electrodes modified by amines with simple chemical structures

Cited by 7 publications

References 39 publications

Mechanism of Light-Soaking Effect in Inverted Polymer Solar Cells with Open-Circuit Voltage Increase

Mechanism of Light-Soaking Effect in Inverted Polymer Solar Cells with Open-Circuit Voltage Increase

An Increase in Open-circuit Photo-voltage of Inverted Polymer Solar Cells by Pre-treatment Applying Forward Bias Under UV-cut Light Irradiation

ITO Modification for Efficient Inverted Organic Solar Cells

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