Molecular doping of low-bandgap-polymer:fullerene solar cells: Effects on transport and solar cells

Tunç, Ali Veysel; Sio, Antonietta De; Riedel, Daniel; Deschler, Felix; Como, Enrico Da; Parisi, J.; Hauff, Elizabeth von

doi:10.1016/j.orgel.2011.11.014

Cited by 73 publications

(44 citation statements)

References 37 publications

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“…Bulk doping of the active layer of bulk heterojunction (BHJ) organic solar cells has recently also attracted interest. Improvements of the power conversion efficiency (PCE) have been reported and attributed to increased charge carrier mobility, photoconductivity, enhanced fill factor (FF) due to trap filling, and favorable formation of photogenerated polarons . The beneficial effect of doping however is not generally well understood, as for example it has been observed that doping lowers the PCE of BHJ Poly(3‐hexylthiophene‐2,5‐diyl):6,6‐Phenyl‐C61‐butyric acid methyl ester (P3HT:PCBM) solar cells .…”

Section: Introductionmentioning

confidence: 99%

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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Section: Introductionmentioning

confidence: 99%

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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“…Molecular doping of organic semiconductors is an increasingly explored avenue for optimizing a range of optoelectronic devices. For instance, molecular dopants can be used to improve charge injection through contact doping and to fill traps in field‐effect transistors (FETs) and organic solar cells . In case of organic thermoelectrics molecular dopants permit to increase the charge carrier density ( n ) and hence tune the performance in terms of electrical conductivity (σ) and Seebeck coefficient (α) .…”

mentioning

confidence: 99%

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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“…Over the past few years, much attention has been focused on the application of molecular dopants for organic electronics, as these materials provide many important benefits across a wide range of electrical devices . For instance, previous studies have reported enhanced mobility in field‐effect transistors (FETs) by trap filling, improved charge injection in light‐emitting diodes (LEDs) and, more recently, superior power‐conversion efficiencies in organic photovoltaics . Molecular doping also affords high conductivities of up to 10 3 S/cm, optical transparency in the visible region and higher thermal power .…”

mentioning

confidence: 99%

Direct Observation of Doping Sites in Temperature‐Controlled, p‐Doped P3HT Thin Films by Conducting Atomic Force Microscopy

et al. 2014

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Molecular doping of low-bandgap-polymer:fullerene solar cells: Effects on transport and solar cells

Cited by 73 publications

References 37 publications

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

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

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

Direct Observation of Doping Sites in Temperature‐Controlled, p‐Doped P3HT Thin Films by Conducting Atomic Force Microscopy

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