Charge Recombination Dynamics in Organic Photovoltaic Systems with Enhanced Dielectric Constant

Hughes, Michael; Rosenthal, Katie D.; Dasari, Raghunath R.; Luginbuhl, Benjamin R.; Yurash, Brett; Marder, Seth R.; Nguyen, Thuc‐Quyen

doi:10.1002/adfm.201901269

Cited by 38 publications

(28 citation statements)

References 39 publications

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“…A power‐law function correlation is given by J sc ∝ P light S , in which S = 1 indicates that the bimolecular recombination process of free carriers is negligible. [ 66,67 ] The values of S are 0.980, 0.992, 0.986, and 0.974 for the devices with 0, 5, 15, and 30 wt% PAEF, respectively. These results suggest that few bimolecular recombination losses occur in the devices, and also reflect the high FF value in the device with 5 wt% PAEF.…”

Section: Resultsmentioning

confidence: 99%

A Universal Method to Enhance Flexibility and Stability of Organic Solar Cells by Constructing Insulating Matrices in Active Layers

Han

Bao

Huang

et al. 2020

Adv Funct Materials

120

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With the rapid development of power conversion efficiency (PCE), flexibility–stability of organic solar cells (OSCs) are becoming one of the primary barriers for commercialization. This work shows that insulating poly(aryl ether) (PAE) resins have highly twisted‐stiff backbones without any side chains, which possess excellent mechanical stability, thermal stability, and good compatibility with organic photovoltaic materials. After introducing 5 wt% PAE resin as supporting matrices into the bulk heterojunction (BHJ) layer, the device yields a high PCE of 16.13%. Importantly, the devices show impressive flexibility and improved stability with passivated morphology, such as PM6/Y6‐based devices with 30 wt% PAE retains the PCE of 15.17% and exhibits enhanced 4.4‐fold elongation at break (25.07%). This is the recorded stretchability of the BHJ layer for OSCs with PCE > 8%, and morphological changes during tensile deformation are first investigated by in situ wide‐angle X‐ray scattering measurements. The PAE matrices strategy exhibits good universality in the other four photovoltaic systems. These results demonstrate that heat‐resistant PAE resins serve as supporting matrices with a tunneling effect into OSCs without sacrificing photovoltaic performance and simultaneously improve the flexibility and stability of devices, which can play an important role in promoting the development of stable and wearable electronics.

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Section: Resultsmentioning

confidence: 99%

A Universal Method to Enhance Flexibility and Stability of Organic Solar Cells by Constructing Insulating Matrices in Active Layers

Han

Bao

Huang

et al. 2020

Adv Funct Materials

120

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“…Although the general merits of a higher dielectric constant are acknowledged, at least with a theoretical perspective, how it affects functional OSC devices is yet incompletely understood. In fact, there are some inconsistencies in previous studies on the role of dielectric constant, [ 24 ] from which unhelpful information is provided. In this review, we hope that the discussed fundamentals of dielectric properties could provide useful information relevant to the current understandings on the role of ε r in OSCs and experimental approaches for mediation of this important parameter.…”

Section: Discussionmentioning

confidence: 99%

“…It is worth noting that the V OC loss due to the dielectric effect is larger than 0.3 V for systems with a small dielectric constant like PCDTBT:PC 71 BM. [ 24 ] While for systems as PDTS‐iI:PC 71 BM which has a larger dielectric constant (close to 5), the loss almost completely vanishes (see Figure 3). [ 47 ]…”

Section: Discussionmentioning

confidence: 99%

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On the Understandings of Dielectric Constant and Its Impacts on the Photovoltaic Efficiency in Organic Solar Cells

Zhang

et al. 2020

Chin. J. Chem.

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Dielectric constant (ε) is an important parameter affecting the power conversion efficiency of organic solar cells (OSC). Increasing ε of bulk heterojunctions in general can benefit the performance of OSCs, as an increased ε will reduce the influence of Coulomb interaction between weakly bound electron‐hole pairs on charge‐transfer states or bimolecular recombination involving mobile carriers to reduce geminate and nongeminate losses. In this review, we overview the current understandings on dielectric constant and its impacts on exciton dissociation and voltage losses in OSCs and summarize recent efforts attempting to modify the dielectric properties of OSC materials through synthetic approaches. We further discuss the commonly adopted techniques for determining the parameter of ε with stressing the testing conditions that may affect the accuracy of results. At last, we suggest that novel experimental methods to improve the dielectric constant and resultant physical processes in OSCs will be appreciated, which helps enrich the existing strategy reservoir toward enhancement of photovoltaic efficiencies.

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“…The measured slope S slightly increases with the rise of temperature approaching 2.0 kT / q which is possible only in the case of dominant SRH recombination in the bulk of the active layer. [ 67–69 ] This example clearly reveals that a significant increase of the effective bandgap of a donor:acceptor blend suppresses bimolecular band‐to‐band recombination and enhances the relative contribution of recombination via deep localized states.…”

Section: Discussionmentioning

confidence: 93%

Temperature and Light Modulated Open‐Circuit Voltage in Nonfullerene Organic Solar Cells with Different Effective Bandgaps

Брус

Schopp

et al. 2020

Advanced Energy Materials

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bandgap systems for the emerging fields of organic semitransparent photovoltaics and near-infrared photodiodes. [9,10] So far, there are no systematic studies on the relationship between the effective bandgap E g,eff , defined by the HOMO of the donor and the LUMO of the acceptor, the density of states (DOS) distribution and multimechanism recombination processes in nonfullerene organic solar cells. However, all mentioned parameters both individually and synergistically are known to be strongly influential on photoelectronic processes and, thus, on the power conversion efficiency (PCE). A specific interest represents the temperature and light intensity dependence of the open-circuit voltage V oc that is selectively sensitive to these parameters and remains immune to the parasitic effects of the series resistance and large shunt. [11-13] Temperature is a macroscopic parameter, which appears in exponential functions in all major equations that describe charge carrier concentration, recombination, and transport processes. This prevalence of the temperature in most equations is mainly caused by the reliance on the Fermi-Dirac distribution or thermally activated processes. [13,14] Hence, temperature is an essential parameter to consider for the analysis of electronic processes in all types of semiconductor materials and devices. [13,15] A controllable change of temperature allows the modulation of basic electronic processes both mechanistically and quantitatively in organic bulk-heterojunction (BHJ) solar cells. In contrast to studies across different devices, uncontrollable fabrication-related deviations in morphology and defect concentrations can be excluded as a parameter of influence. However, in OPVs, the temperature effect is rarely studied and if so, only to inspect the temperature-dependent trends for the main photoelectric parameters (open circuit voltage (V oc), short circuit current density (J sc), fill factor (FF)) and PCE of organic BHJ solar cells. [16-21] Even less attention has been paid to the investigation of temperature-dependent generationrecombination processes in BHJ layers and, specifically, at their interfaces with electrical contacts. [22-24] In this contribution we analyzed temperature and light modulated V oc in a series of nonfullerene BHJ solar cells with conventional or inverted device architecture and a systematically tuned effective bandgap E g,eff in a wide range from 1.0 to 1.62 eV. The temperature-dependent V oc versus light intensity slopes The relationship of the temperature-light intensity dependence of opencircuit voltage V oc in nonfullerene-based organic solar cells with their material characteristics and multimechanism recombination parameters is described. The systematic variation of the effective bandgap E g,eff and the electrode layers allows the observation of different relative contributions of bimolecular, bulk, and surface trap-assisted recombination mechanisms. The complementary advantages of the analytical model and the established voltage-impedance spectroscopy techn...

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Charge Recombination Dynamics in Organic Photovoltaic Systems with Enhanced Dielectric Constant

Cited by 38 publications

References 39 publications

A Universal Method to Enhance Flexibility and Stability of Organic Solar Cells by Constructing Insulating Matrices in Active Layers

A Universal Method to Enhance Flexibility and Stability of Organic Solar Cells by Constructing Insulating Matrices in Active Layers

On the Understandings of Dielectric Constant and Its Impacts on the Photovoltaic Efficiency in Organic Solar Cells

Temperature and Light Modulated Open‐Circuit Voltage in Nonfullerene Organic Solar Cells with Different Effective Bandgaps

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