Understanding the External Quantum Efficiency of Organic Homo‐Tandem Solar Cells Utilizing a Three‐Terminal Device Architecture

Bahro, Daniel; Koppitz, Manuel; Mertens, Adrian; Glaser, Konstantin; Mescher, Jan; Colsmann, Alexander

doi:10.1002/aenm.201501019

Cited by 31 publications

(27 citation statements)

References 24 publications

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“…The presence of a low shunt resistance in one or more subcells would result in a higher EQE. [49] The EQE of the triple measured without bias light is shown in Figure 4 with black dots, and nicely follows the lower envelope of the EQE of the subcells.…”

Section: Eqe Of the Triple-junction Using Bias Lightsupporting

confidence: 58%

Accurate Characterization of Triple‐Junction Polymer Solar Cells

Rasi

Hendriks

Wienk

et al. 2017

Advanced Energy Materials

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organic semiconductors have been developed to absorb light into the near infrared region. [8] The gain in spectral coverage and short-circuit current density (J SC ) in the cells is, however, counteracted by an unavoidable loss in the open-circuit voltage (V OC ) when the bandgap decreases. [9] Given the intrinsic limits of singlejunction organic solar cells, there has been an increasing interest to develop multijunction architectures. [10] This paves the way to efficient solar cells by an improved utilization of photon energy. In a multijunction solar cell sunlight is spectrally distributed over two, or more subcells such that highenergy photons are absorbed in a wide bandgap subcell and low-energy photons in a small bandgap subcell. This reduces the thermalization losses for high-energy photons and the transmission losses for the low-energy photons. Most studies have focused on the tandem architecture, in which identical or different absorber layers are used, resulting in maximum efficiencies in the range of 10-13%. [11][12][13][14][15][16][17][18][19][20][21][22] At least conceptually, stacking three absorber layers in a triple-junction solar cell can lead to a further increase in efficiency. There are few examples of triple-junction organic solar cells. [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] The gain in efficiency achieved by these triple-junction devices was not always accompanied by a critical analysis of the measured performance. In a recent publication, Timmreck et al. methodically analyzed the literature on tandem organic solar cells, shedding light on the fact that the vast majority of the publications on organic tandem cells lacked a proper characterization. [42] Although the paper focused attention on the tandem structure, the argumentations provided can reasonably be extended to the case of triple-junctions. At present, the characterization of organic triple-junctions is often limited to measuring the J−V characteristics under simulated solar radiation and determining the external quantum efficiency (EQE) using different light sources to optically bias the subcells. [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] Nevertheless, organic materials commonly employed for solar cells feature peculiar characteristics that necessitate special attention for their EQE measurement. [42][43][44] An accurate analysis of the effect of bias light and bias voltage on the EQE of triple-junction organic solar cells is necessary.Detailed protocols for the characterization of triple-junction solar cells are available in the literature. [45] For many inorganic triple-junction solar cells the effect of bias voltage on the spectral response is very small, which makes correction for bias voltage not critical. [45] The aim of this work is to provide a characterization protocol for organic triple-junction solar cells that take into account the uniqueness of these particular materials. In order to do so, we combine optical and electrical modeling, use

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Section: Eqe Of the Triple-junction Using Bias Lightsupporting

confidence: 58%

Accurate Characterization of Triple‐Junction Polymer Solar Cells

Rasi

Hendriks

Wienk

et al. 2017

Advanced Energy Materials

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“…Measuring the external quantum efficiency (EQE) spectrum of a tandem cell gives insight in the current generated by each subcell, but also in the structural integrity of the layers, especially on the presence of current leakage paths in one or more photoactive layers. In an ideal tandem cell, the EQE measured without bias light should follow the lower envelope of the EQEs of the subcells, determined using representative bias light . In case of a leakage, the EQE without bias light can be substantially higher .…”

Section: Resultsmentioning

confidence: 99%

“…In an ideal tandem cell, the EQE measured without bias light should follow the lower envelope of the EQEs of the subcells, determined using representative bias light. [56] In case of a leakage, the EQE without bias light can be substantially higher. [56] Figure 5 shows that the EQEs of BHJ2-BHJ4 (best tandem with PEIE as ETL) and BHJ5-BHJ8 (best tandem with ZnO as ETL) measured without light bias are very close to the expected behavior.…”

Section: Tandems Solar Cellsmentioning

confidence: 99%

A Universal Route to Fabricate n‐i‐p Multi‐Junction Polymer Solar Cells via Solution Processing

et al. 2018

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The interconnection layer (ICL) that connects adjacent subcells electrically and optically in solution‐processed multi‐junction polymer solar cells must meet functional requirements in terms of work functions, conductivity, and transparency, but also be compatible with the multiple layer stack in terms of processing and deposition conditions. Using a combination of poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate, diluted in near azeotropic water/n‐propanol dispersions as hole transport layer, and ZnO nanoparticles, dispersed in isoamyl alcohol as electron transport layer, a novel, versatile ICL has been developed for solution‐processed tandem and triple‐junction solar cells in an n‐i‐p architecture. The ICL has been incorporated in six different tandem cells and three different triple‐junction solar cells, employing a range of different polymer‐fullerene photoactive layers. The new ICL provided an essentially lossless contact in each case, without the need of adjusting the formulations or deposition conditions. The approach permitted realizing complex devices in good yields, providing a power conversion efficiency up to 10%.

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“…EQE of subcells of the tandem solar cell was tested on a system using a 150 W xenon lamp fitted with a monochromator (Cornerstone 74004) as a monochromatic light source. The method used to measure the EQE by introducing a conductive intermediate polymer as the third electrode to access the EQE of subcells independently as reported by Tong et al and Bahro et al…”

Section: Methodsmentioning

confidence: 99%

Incorporation of Hydrogen Molybdenum Bronze in Solution‐Processed Interconnecting Layer for Efficient Nonfullerene Tandem Organic Solar Cells

et al. 2019

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Tandem solar cells are attractive because they can break the Shockley–Queisser efficiency limit of single‐junction cells. However, it is still quite challenging to fabricate efficient nonfullerene tandem organic solar cells (OSCs) because of their complicated and vulnerable multilayers and interfaces. The interconnecting layer (ICL) between two subcells is the key part in efficient tandem solar cells, which should be designed properly based on the property of active layers. Herein, the incorporation of hydrogen molybdenum bronze (HxMoO3) between the bottom active layer and PEDOT:PSS/ZnO to form a new ICL is proposed. The contribution of the HxMoO3 is two fold: 1) it can well wet the hydrophobic active layer surface and form a uniform film. It provides a hydrophilic surface for the following deposition of PEDOT:PSS; 2) the HxMoO3 has a high work function of 5.4 eV that is higher than PEDOT:PSS (5.0 eV) and can extract holes more efficiently from the active layer with the deep highest occupied molecular orbital energy level. Nonfullerene tandem solar cells with a high fill factor of 76.0% and power conversion efficiency of 15.03% are obtained with this ICL.

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Understanding the External Quantum Efficiency of Organic Homo‐Tandem Solar Cells Utilizing a Three‐Terminal Device Architecture

Cited by 31 publications

References 24 publications

Accurate Characterization of Triple‐Junction Polymer Solar Cells

Accurate Characterization of Triple‐Junction Polymer Solar Cells

A Universal Route to Fabricate n‐i‐p Multi‐Junction Polymer Solar Cells via Solution Processing

Incorporation of Hydrogen Molybdenum Bronze in Solution‐Processed Interconnecting Layer for Efficient Nonfullerene Tandem Organic Solar Cells

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