Imaging of morphological changes and phase segregation in doped polymeric semiconductors

Deschler, Felix; Riedel, Daniel; Deák, András; Ecker, Bernhard; Hauff, Elizabeth von; Como, Enrico Da

doi:10.1016/j.synthmet.2014.11.037

Cited by 32 publications

(37 citation statements)

References 45 publications

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“…Doping of the polymer with F4TCNQ leads to a shift of the out‐of‐plane 100 diffraction from 3.6 to 2.9 nm −1 as a result of incorporation of the dopant in the polymer crystals, which has also been observed for P3HT doped with F4TCNQ. Interestingly, we do not observe an additional diffraction peak at ≈7.7 nm −1 from F4TCNQ crystals (Figure S10, Supporting Information) at higher dopant fractions as has been reported for P3HT:F4TCNQ . We argue that the dopant stays molecularly dispersed in the polymer film even after addition of a larger dopant fraction and does not crystallize.…”

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confidence: 79%

Polar Side Chains Enhance Processability, Electrical Conductivity, and Thermal Stability of a Molecularly p‐Doped Polythiophene

et al. 2017

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Molecular doping of organic semiconductors is critical for optimizing a range of optoelectronic devices such as field‐effect transistors, solar cells, and thermoelectric generators. However, many dopant:polymer pairs suffer from poor solubility in common organic solvents, which leads to a suboptimal solid‐state nanostructure and hence low electrical conductivity. A further drawback is the poor thermal stability through sublimation of the dopant. The use of oligo ethylene glycol side chains is demonstrated to significantly improve the processability of the conjugated polymer p(g42T‐T)—a polythiophene—in polar aprotic solvents, which facilitates coprocessing of dopant:polymer pairs from the same solution at room temperature. The use of common molecular dopants such as 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) and 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) is explored. Doping of p(g42T‐T) with F4TCNQ results in an electrical conductivity of up to 100 S cm−1. Moreover, the increased compatibility of the polar dopant F4TCNQ with the oligo ethylene glycol functionalized polythiophene results in a high degree of thermal stability at up to 150 °C.

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supporting

confidence: 79%

Polar Side Chains Enhance Processability, Electrical Conductivity, and Thermal Stability of a Molecularly p‐Doped Polythiophene

et al. 2017

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“…[38,51] Based on our studies, we suggest that smaller, more efficient dopants can potentially further increase the PCE of BHJs. Due to the generally low dielectric constant of organic semiconductors, dopant ions can form Coulomb traps, limiting the efficiency of free-carrier generation and hindering charge transport.…”

Section: Resultsmentioning

confidence: 75%

Trade‐Off between Trap Filling, Trap Creation, and Charge Recombination Results in Performance Increase at Ultralow Doping Levels in Bulk Heterojunction Solar Cells

Shang

Heumueller

Prasanna

et al. 2016

Advanced Energy Materials

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Doping of organic bulk heterojunction solar cells has the potential to improve their power conversion efficiency (PCE). Deconvoluting the effect of doping on charge transport, recombination, and energetic disorder remains challenging. It is demonstrated that molecular doping has two competing effects: on one hand, dopant ions create additional traps while on the other hand free dopant-induced charges fill deep states possibly leading to V OC and mobility increases. It is shown that molar dopant concentrations as low as a few parts per million can improve the PCE of organic bulk heterojunctions. Higher concentrations degrade the performance of the cells. In doped cells where PCE is observed to increase, such improvement cannot be attributed to better charge transport. Instead, the V OC increase in unannealed P3HT:PCBM cells upon doping is indeed due to trap filling, while for annealed P3HT:PCBM cells the change in V OC is related to morphology changes and dopant segregation.In PCDTBT:PC70BM cells, the enhanced PCE upon doping is explained by changes in the thickness of the active layer. This study highlights the complexity of bulk doping in organic solar cells due to the generally low doping efficiency and the constraint on doping concentrations to avoid carrier recombination and adverse morphology changes.

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“…As shown in Figure 3, doping the PTAA film by 1 wt% F4-TCNQ reduced the device series resistance from 9.07 Ω cm 2 for non-doped PTAA to 6.07 Ω cm 2 . Further increasing F4-TCNQ doping level to 10 wt% increased the device series resistance to 9.77 Ω cm 2 , most likely caused by the increased aggregation of F4-TCNQ [28][29][30][31]. The series resistance derived from the J-V curve slope can be an indirect evidence for the doping effect because it represents the series resistance of the whole device rather than the PTAA films.…”

Section: Resultsmentioning

confidence: 99%

Doped hole transport layer for efficiency enhancement in planar heterojunction organolead trihalide perovskite solar cells

2015

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We demonstrated the efficiency of a solution-processed planar heterojunction organometallic trihalide perovskite solar cell can be increased to 17.5% through doping the hole transporting layer for reducing the resistivity. Doped Poly(triaryl amine) (PTAA) by 2,3,5,6-Tetrafluoro-7,7,8,8-Tetracyanoquinodimethane (F4-TCNQ) reduced device series resistance by three-folds, increasing the device fill factor to 74%, open circuit voltage to 1.09 V without sacrificing the short circuit current. This study reveals that the high resistivity of currently broadly applied polymer hole transport layer limits the device efficiency, and points a new direction to improve the device efficiency.

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Imaging of morphological changes and phase segregation in doped polymeric semiconductors

Cited by 32 publications

References 45 publications

Polar Side Chains Enhance Processability, Electrical Conductivity, and Thermal Stability of a Molecularly p‐Doped Polythiophene

Polar Side Chains Enhance Processability, Electrical Conductivity, and Thermal Stability of a Molecularly p‐Doped Polythiophene

Trade‐Off between Trap Filling, Trap Creation, and Charge Recombination Results in Performance Increase at Ultralow Doping Levels in Bulk Heterojunction Solar Cells

Doped hole transport layer for efficiency enhancement in planar heterojunction organolead trihalide perovskite solar cells

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