Role of Polymer Fractionation in Energetic Losses and Charge Carrier Lifetimes of Polymer: Fullerene Solar Cells

Baran, Derya; Vezie, Michelle S.; Gasparini, Nicola; Deledalle, Florent; Yao, Jianguo; Schroeder, Bob C.; Bronstein, Hugo; Ameri, Tayebeh; Kirchartz, Thomas; McCulloch, Iain; Nelson, Jenny; Brabec, Christoph J.

doi:10.1021/acs.jpcc.5b05709

Cited by 23 publications

(22 citation statements)

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“…This implies that both the donor and acceptor photoexcitations can contribute to the achievable open circuit voltage as well as the photovoltaic performance of BHJ OSCs; this agrees with our earlier results [45] [68], 0.34-0.44 V for a range of donor-acceptor blends [69], 0.38 V for OC 1 C 10 -PPV:PCBM solar cells [12], and 0.30-0.60 V for BHJ OSCs [20]. Other low voltage offsets ( E DA/q − V j OC ) that have been reported recently are 0.25 V for an evaporated bilayer OSC [70], 0.23 V and 0.26 V for diketopyrrolopyrrole-thieno[2,3-f]benzofuran (DTD):PC 60 BM and DTD:naphthalene diimide acceptor-polymer (N2200) systems, respectively [71], and 0.34-0.40 V for BHJ OSCs [72], with which our calculated values also somewhat agree in the range.…”

Section: Discussionsupporting

confidence: 92%

Study of the Contributions of Donor and Acceptor Photoexcitations to Open Circuit Voltage in Bulk Heterojunction Organic Solar Cells

Yeboah

Singh

2017

Electronics

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Abstract:One of the key parameters in determining the power conversion efficiency (PCE) of bulk heterojunction (BHJ) organic solar cells (OSCs) is the open circuit voltage (V OC ). The processes of exciting the donor and acceptor materials individually in a BHJ OSC are investigated and are found to produce two different expressions for V OC s. Using the contributions of electron and hole quasi-Fermi levels and charge carrier concentrations, the two different V OC expressions are derived as functions of the energetics of the donor and acceptor materials and the photo-generated charge carrier concentrations, and calculated for a set of donor-acceptor blends. The simultaneous excitation of both the donor and acceptor materials is also considered and the corresponding V OC , which is different from the above two, is derived. The V OC calculated from the photoexcitation of the donor is found to be somewhat comparable with that obtained from the photoexcitation of the acceptor in most combinations of the donor and acceptor materials considered here. It is also found that the V OC calculated from the simultaneous excitations of donor and acceptor in BHJ OSCs is also comparable with the other two V OC s. All three V OC s thus derived produce similar results and agree reasonably well with the measured values. All three V OC s depend linearly on the concentration of the photoexcited charge carriers and hence incident light intensity, which agrees with experimental results. The outcomes of this study are expected to help in finding materials that may produce higher V OC and hence enhanced PCE in BHJ OSCs.

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Section: Discussionsupporting

confidence: 92%

Study of the Contributions of Donor and Acceptor Photoexcitations to Open Circuit Voltage in Bulk Heterojunction Organic Solar Cells

Yeboah

Singh

2017

Electronics

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“…In the case of SML06 only, the band gap is reduced by up to 0.05 eV upon SVA. This is due to the greater ability of this molecule to crystallise upon annealing, also suggested by the domain growth in Figure S1and The non-radiative voltage loss ∆V oc,nr of these materials ranges from 0.29 to 0.37 V and in the best cases is lower than the lowest previously published values for polymer:fullerene solar cells which were 0.32 V for an indacenodithiophene polymer 29 The combination of low ∆V oc,abs and ∆V oc,nr explains the high open-circuit voltages that we could achieve with these materials. Whilst the origin of the relatively low non-radiative loss is not known, it is consistent with the higher degree of purification possible for small molecules than for polymers, which could reduce the defect density, and also with the lower degree of disorder in electronic state energies that is expected in small molecules due to their limited conformational phase space .…”

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confidence: 67%

Low Open-Circuit Voltage Loss in Solution-Processed Small-Molecule Organic Solar Cells

et al. 2016

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We analyze the voltage losses at open circuit in solutionprocessed, small-molecule:fullerene blend solar cells, using electroluminescence and external quantum efficiency measurements and the reciprocity relationship between light absorption and emission. For solar cells made from oligothienylenevinylene-based donors and phenyl-C 71 butyric acid methyl ester (PC 71 BM), we find that the voltage loss due to the finite breadth of the absorption edge is remarkably small, less than 0.01 eV in the best cases, while the voltage loss due to nonradiative recombination reaches 0.29 eV, one of the smallest values reported for an organic solar cell. As a result, the open-circuit voltage reaches around 1.0 V for an optical gap of 1.6 eV, greatly exceeding the voltage of a high-performance polymer-based system with similar optical gap. We assign the remarkably small absorption broadening loss to a low degree of energetic disorder in the small-molecule system that allows efficient charge separation at a lower driving force than in typical conjugated polymer blends.

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“…[10,11] At room temperature, ΔV oc of CH 3 NH 3 PbBr 3 solar cells deliver a value of 0.45 V, which is much larger than the corresponding value in CH 3 NH 3 PbI 3 devices (0.23-0.35 V) [11,15] and even larger than in common organic solar cells (0.30-0.43 V). [10,25] Furthermore, ΔV oc remains either constant or even slightly increases with lower temperatures. Nonradiative recombination can be well suppressed at low temperatures, typically resulting in a significant enhancement in V oc .…”

Section: Resultsmentioning

confidence: 96%

Exploring the Limiting Open‐Circuit Voltage and the Voltage Loss Mechanism in Planar CH₃NH₃PbBr₃ Perovskite Solar Cells

Chen

Hou

Chen

et al. 2016

Advanced Energy Materials

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spectral range for singe junction solar cells, and according to the Shockley-Queisser model the photocurrent is expected to be below 9.7 mA cm −2 . [2] However, a relatively high V oc of 1.4-1.5 V was reported, which makes this material system a great candidate for applications such as tandem configuration or other systems requiring spectral splitting. [2][3][4][5][6][7] Significant efforts were undertaken to investigate and optimize the V oc of CH 3 NH 3 PbBr 3 solar cells. [2][3][4][5][6][7][8][9] Engineering advanced hole transport layers (HTL) such as carbon nanotubes, [2] 2,2′,7,7′-tetrakis(N,Ndi-p-methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD), [5,7] poly (indenofluoren-8-triarylamine) (PIF8-TAA), [3,4] and 4,4-bis(N-carbazolyl)-1,1-biphenyl (CBP) [6] resulted in V oc within a range of 1.4-1.5 V for solution-processed perovskite solar cells. Sheng et al. demonstrated a high V oc of 1.45 V using the architecture TiO 2 / CH 3 NH 3 PbBr 3 /spiro-OMeTAD via a vaporassisted depositon. [7] Kim et al. modified the TiO 2 surfaces with carboxyl groups and employed no HTL for CH 3 NH 3 PbBr 3 solar cells, producing a V oc of 1.37 V. [8] Dymshits et al. reported a V oc of 1.35 V for Al 2 O 3 /CH 3 NH 3 PbBr 3 perovskite solar cells without HTL. [9] These studies focused more on the V oc improvement via interface engineering and via optimizing the CH 3 NH 3 PbBr 3 film quality. Despite significant progress toward unraveling the V oc limitation of CH 3 NH 3 PbBr 3 solar cells, the limiting V oc (V oc,rad ) is still unknown to the best of our knowledge. Besides, Perovskite solar cells based on CH

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Role of Polymer Fractionation in Energetic Losses and Charge Carrier Lifetimes of Polymer: Fullerene Solar Cells

Abstract: Non-radiative recombination reduces the open-circuit voltage relative to its theoretical limit and leads to reduced luminescence emission at a given excitation. Therefore it is possible to correlate

Cited by 23 publications

References 47 publications

Study of the Contributions of Donor and Acceptor Photoexcitations to Open Circuit Voltage in Bulk Heterojunction Organic Solar Cells

Study of the Contributions of Donor and Acceptor Photoexcitations to Open Circuit Voltage in Bulk Heterojunction Organic Solar Cells

Low Open-Circuit Voltage Loss in Solution-Processed Small-Molecule Organic Solar Cells

Exploring the Limiting Open‐Circuit Voltage and the Voltage Loss Mechanism in Planar CH₃NH₃PbBr₃ Perovskite Solar Cells

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Role of Polymer Fractionation in Energetic Losses and Charge Carrier Lifetimes of Polymer: Fullerene Solar Cells

Abstract: Non-radiative recombination reduces the open-circuit voltage relative to its theoretical limit and leads to reduced luminescence emission at a given excitation. Therefore it is possible to correlate

Cited by 23 publications

References 47 publications

Study of the Contributions of Donor and Acceptor Photoexcitations to Open Circuit Voltage in Bulk Heterojunction Organic Solar Cells

Study of the Contributions of Donor and Acceptor Photoexcitations to Open Circuit Voltage in Bulk Heterojunction Organic Solar Cells

Low Open-Circuit Voltage Loss in Solution-Processed Small-Molecule Organic Solar Cells

Exploring the Limiting Open‐Circuit Voltage and the Voltage Loss Mechanism in Planar CH3NH3PbBr3 Perovskite Solar Cells

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Exploring the Limiting Open‐Circuit Voltage and the Voltage Loss Mechanism in Planar CH₃NH₃PbBr₃ Perovskite Solar Cells