Increasing Polymer Solar Cell Fill Factor by Trap‐Filling with F4‐TCNQ at Parts Per Thousand Concentration

Yan, Han; Manion, Joseph G.; Yuan, Mingjian; Arquer, F. Pelayo Garcı́a de; McKeown, George R.; Beaupré, Serge; Leclerc, Mario; Sargent, Edward H.; Seferos, Dwight S.

doi:10.1002/adma.201601553

Cited by 91 publications

(116 citation statements)

References 46 publications

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“…The J ‐ V data for 20 different but simultaneously fabricated OPV cells based on PM6:Y6:PC 71 BM BHJs doped with 0.004 wt% of BV, are presented in Figure S16 (Supporting Information), while a summary of cell parameters is given in Table S10 (Supporting Information). In Figure 4c, we summarize the PCE values reported to date for OPVs based on molecularly doped BHJs 17,18,20,22,47,48. Among these studies Xu et al,22 is the only one to describe the impact of n‐type doping in all‐polymer OPVs with the remaining reporting the use of p‐type dopants.…”

Section: Summary Of Operating Parameters Of Solar Cells Based On Pm6:mentioning

confidence: 99%

17.1% Efficient Single‐Junction Organic Solar Cells Enabled by n‐Type Doping of the Bulk‐Heterojunction

et al. 2020

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Molecular doping is often used in organic semiconductors to tune their (opto)electronic properties. Despite its versatility, however, its application in organic photovoltaics (OPVs) remains limited and restricted to p‐type dopants. In an effort to control the charge transport within the bulk‐heterojunction (BHJ) of OPVs, the n‐type dopant benzyl viologen (BV) is incorporated in a BHJ composed of the donor polymer PM6 and the small‐molecule acceptor IT‐4F. The power conversion efficiency (PCE) of the cells is found to increase from 13.2% to 14.4% upon addition of 0.004 wt% BV. Analysis of the photoactive materials and devices reveals that BV acts simultaneously as n‐type dopant and microstructure modifier for the BHJ. Under optimal BV concentrations, these synergistic effects result in balanced hole and electron mobilities, higher absorption coefficients and increased charge‐carrier density within the BHJ, while significantly extending the cells' shelf‐lifetime. The n‐type doping strategy is applied to five additional BHJ systems, for which similarly remarkable performance improvements are obtained. OPVs of particular interest are based on the ternary PM6:Y6:PC71BM:BV(0.004 wt%) blend for which a maximum PCE of 17.1%, is obtained. The effectiveness of the n‐doping strategy highlights electron transport in NFA‐based OPVs as being a key issue.

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Section: Summary Of Operating Parameters Of Solar Cells Based On Pm6:mentioning

confidence: 99%

17.1% Efficient Single‐Junction Organic Solar Cells Enabled by n‐Type Doping of the Bulk‐Heterojunction

et al. 2020

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“…[33] More recently, these absorptions are also thought to be associated with charge-transfer (CT) states in BHJs. [42][43][44][45][46] Besides trap density, the added fullerene molecules give rise to new features in the PDS spectra. However, in the present study, before the percolated pathways of PC 71 BM have been formed in low doping ratios, the CT states are disconnected from the charge separation states and therefore acting as electron traps to hinder the carrier transport.…”

Section: Correlation Between Subgap Optical Absorption and Fill Factomentioning

confidence: 99%

Using Ultralow Dosages of Electron Acceptor to Reveal the Early Stage Donor–Acceptor Electronic Interactions in Bulk Heterojunction Blends

Cheung

et al. 2017

Advanced Energy Materials

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Tuning the donor–acceptor (D–A) weight ratio is an essential step to optimize the performance of a bulk heterojunction (BHJ) solar cell. The unoptimized regime with a low acceptor concentration is generally unexplored despite it may reveal the early stage electronic D–A interactions. In this study, PTB7:PC71BM is used to examine factors that limit the device performance in unoptimized regime. The key limiting factor is the creation of traps and localized states originated from fullerene molecules. Photothermal deflection spectroscopy is used to quantify the trap density. Starting with pristine PTB7, addition of small concentration of fullerene increases the electron trap density and lowers the electron mobility. When the D–A weight ratio reaches 1:0.1, fullerene percolation occurs. There is an abrupt drop in trap density and simultaneously a six orders of magnitude increase in the electron mobility. Furthermore, the fill factors of the corresponding photovoltaic devices are found to anticorrelate with the trap density. This study reveals that electron trapping is the key limiting factor for unoptimized BHJ solar cells in low fullerene regime.

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“…[3,4] To complement materials design, doping is a common approach to tune the properties of semiconductors in order to engineer their operation in electronic devices. Improvements of the power conversion efficiency (PCE) have been reported and attributed to increased charge carrier mobility, photoconductivity, [9,10] enhanced fill factor (FF) due to trap filling, [11] and favorable formation of photogenerated polarons. [5,6] Thus doping finds many applications in organic transistors and light emitting diodes, where dopants are used to reduce contact resistance and in transport layers.…”

Section: Doi: 101002/aenm201601149mentioning

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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Increasing Polymer Solar Cell Fill Factor by Trap‐Filling with F4‐TCNQ at Parts Per Thousand Concentration

Cited by 91 publications

References 46 publications

17.1% Efficient Single‐Junction Organic Solar Cells Enabled by n‐Type Doping of the Bulk‐Heterojunction

17.1% Efficient Single‐Junction Organic Solar Cells Enabled by n‐Type Doping of the Bulk‐Heterojunction

Using Ultralow Dosages of Electron Acceptor to Reveal the Early Stage Donor–Acceptor Electronic Interactions in Bulk Heterojunction Blends

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

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