Synergistic Effect of Dielectric Property and Energy Transfer on Charge Separation in Non‐Fullerene‐Based Solar Cells

Li, Pandeng; Fang, Jin; Wang, Yusheng; Manzhos, Sergei; Cai, Lei; Song, Zheheng; Li, Yajuan; Song, Tao; Wang, Xuechun; Guo, Xia; Zhang, Maojie; Ma, Dongling; Sun, Baoquan

doi:10.1002/anie.202103357

Cited by 35 publications

(29 citation statements)

References 62 publications

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“…Although low-frequency dielectric constants approaching 10 (compared to ∼4 for most organics) have been reported for NFAs, there is currently no conclusive evidence that this is generally the case at the GHz and optical frequencies of interest here. 14,15 We argue that claims of efficient, barrierless charge separation at zero driving force are in part due to inaccurate metrics for calculating the driving force or do not take into account all sources of potential energy. Major contributors to this issue are the lack of characterization standards between laboratories and the use of varied quantitiesfor example, ionization potential (IP)/ electron affinity (EA) offsets versus charge transfer (CT) state energieswhich make interstudy comparisons arduous.…”

mentioning

confidence: 99%

Reconciling the Driving Force and the Barrier to Charge Separation in Donor–Nonfullerene Acceptor Films

et al. 2021

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We investigate the dependence of charge yields on the driving force for photoinduced electron transfer in a series of all-small-molecule, semiconducting films made from indacenodithiophene nonfullerene acceptors (IDT NFAs). In contrast to reports of efficient, barrierless charge separation at near zero driving force for NFA-containing organic photovoltaics, we find that barrierless charge separation occurs only if the driving force is sufficient to overcome the Coulomb potential, ≥300 meV, based on time-resolved microwave conductivity and PL quenching measurements of 5 mmolal sensitized and 700 mmolal blended films comprising IDT NFAs paired with three different donors. This discrepancy with recent literature is caused by a difference in the way that we calculate driving force. Far from being semantic, the driving force calculation is crucial because its value controls the mechanisms needed to explain experimental observations. We provide a candid assessment of the uncertainties for our methods and popular ones used in the literature and emphasize the importance of standardizing methods across this field.

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confidence: 99%

Reconciling the Driving Force and the Barrier to Charge Separation in Donor–Nonfullerene Acceptor Films

et al. 2021

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“…ϵ 0 is the vacuum dielectric constant ( ϵ 0 ≈8.854×10 −12 F m −1 ), ϵ r is the relative dielectric constant of the active layer (PM6 : Y6≈3.94), [36] f is the frequency, k is the Boltzmann constant, and T is room temperature ( kT ≈0.026 eV). The bound energy of excitons ( E b ) in the excited state is usually about 0.3 eV [37] . It can be obtained that in OSCs with bulk heterojunctions, theoretical exciton separation requires an internal electric field of 50–100 V μm −1 .…”

Section: Resultsmentioning

confidence: 99%

Ferroelectric Polymer Drives Performance Enhancement of Non‐fullerene Organic Solar Cells

Deng

Huang

et al. 2022

Angew Chem Int Ed

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Enhancing the built-in electric field to promote charge dynamitic process is of great significance to boost the performance of the non-fullerene organic solar cells (OSCs), which has rarely been concerned. In this work, we introduced a cheap ferroelectric polymer as an additive into the active layers of non-fullerene OSCs to improve the device performance. An additional and permanent electrical field was produced by the polarization of the ferroelectric dipoles, which can substantially enhance the built-in electric field. The promoted exciton separation, significantly accelerated charge transport, reduced the charge recombination, as well as the optimized film morphology were observed in the device, leading to a significantly improved performance of the PVDF-modified OSCs with various active layers, such as PM6 : Y6, PM6 : BTP-eC9, PM6 : IT-4F and PTB7-Th : Y6. Especially, a record efficiency of 17.72 % for PM6 : Y6-based OSC and an outstanding efficiency of 18.17 % for PM6 : BTP-eC9-based OSC were achieved.

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“…By fitting the data with power‐law J sc ∝ Pa light, the a values of the terpolymer‐based OSCs are closer to 1 compared to that of PCE10:Y6, PCE10‐2F:Y6, and PCE10‐2Cl:Y6 OSCs, indicating that bimolecular charge recombination is decreased in the terpolymer‐based OSCs. [ 37 ]…”

Section: Resultsmentioning

confidence: 99%

Novel Narrow Bandgap Terpolymer Donors Enables Record Performance for Semitransparent Organic Solar Cells Based on All‐Narrow Bandgap Semiconductors

Huang

Zhang

Cheng

et al. 2021

Adv Funct Materials

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Semitransparent organic solar cells (ST‐OSCs) based on all narrow bandgap (all‐NBG) semiconductors are attractive for building integration. Unfortunately, advanced NBG Y‐series acceptors cannot well match with the NBG donors, resulting from their mismatched energy levels and poor compatibility. Herein, a facile terpolymer design strategy is adopted to improve the matching of Y6 with efficient NBG polymer donor PCE10. F or Cl atom functionalized benzodithiophene (BDT) are introduced into the PCE10 matrix to afford two series of terpolymers, namely PCE10‐BDT2F and PCE10‐BDT2Cl. Compared with PCE10, all terpolymers show deeper energy levels, higher extinction coefficients, enhanced face‐on orientation, and better compatibility with Y6. Consequently, significant breakthroughs are achieved for both opaque and semitransparent devices. Particularly, a record power conversion efficiency (PCE) of 13.80% is achieved by PCE10‐BDT2F:Y6‐based device, nearly 40% higher than PCE10:Y6‐based device. ST‐OSCs also achieve impressive PCEs of 12.00% and 10.85% with average visible transmittance (AVT) of 30.98% and 41.08%, respectively, and both PCEs are the highest values with AVT over 30% and 40%. An outstanding light utilization efficiency (LUE) of 4.46% further demonstrates the successful balance of PCE and AVT. These results demonstrate that the design of NBG terpolymers is a facile and highly encouraging strategy for promoting breakthroughs in ST‐OSCs.

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Synergistic Effect of Dielectric Property and Energy Transfer on Charge Separation in Non‐Fullerene‐Based Solar Cells

Cited by 35 publications

References 62 publications

Reconciling the Driving Force and the Barrier to Charge Separation in Donor–Nonfullerene Acceptor Films

Reconciling the Driving Force and the Barrier to Charge Separation in Donor–Nonfullerene Acceptor Films

Ferroelectric Polymer Drives Performance Enhancement of Non‐fullerene Organic Solar Cells

Novel Narrow Bandgap Terpolymer Donors Enables Record Performance for Semitransparent Organic Solar Cells Based on All‐Narrow Bandgap Semiconductors

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