Achieving Balanced Crystallization Kinetics of Donor and Acceptor by Sequential‐Blade Coated Double Bulk Heterojunction Organic Solar Cells

Wang, Yilin; Wang, Xiaohui; Lin, Baojun; Bi, Zhaozhao; Zhou, Xiaobo; Naveed, Hafiz Bilal; Zhou, Ke; Yan, Hongping; Tang, Zheng; Ma, Wei

doi:10.1002/aenm.202000826

Cited by 87 publications

(92 citation statements)

References 65 publications

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“…[37][38][39][40] Despite these attractive characteristics, sequentially deposited (SD) OSCs have received less attention and their efficiencies lag behind those of the conventional BHJ (C-BHJ) OSCs prepared with a single casting process. [41][42][43][44][45][46][47] Therefore, it is imperative to demonstrate the general applicability of sequential deposition as an effective yet simpler method for achieving desired BHJ morphology and device performance.…”

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confidence: 99%

A Generally Applicable Approach Using Sequential Deposition to Enable Highly Efficient Organic Solar Cells

Gao

et al. 2020

Small Methods

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Organic solar cells (OSCs) have attracted enormous research interest due to their promise for the realization of lightweight, mechanically flexible, and portable power generators using low-cost printing techniques. [1-3] Solution-processable OSCs are typically based on a bulk heterojunction (BHJ) architecture comprising electron-donating (donor) and electronaccepting (acceptor) semiconductors. In recent years, the continual development of innovative photovoltaic materials, [4-14] device and interface engineering [15-19] in conjunction with better understanding of fundamental mechanisms [20-23] have contributed to the rapid progress of BHJ OSCs. Their power conversion efficiencies (PCEs) have now reached more than 17% for both single-junction [24-28] and tandem [29] devices, providing great prospects for practical applications. The achievable performance of OSCs is strongly dependent on the BHJ blend morphology, wherein the donor and acceptor are expected to form nanoscale phase separation and bicontinuous pathways for maximizing charge generation and transport. [30] At present, BHJ photoactive layers are fabricated normally via spin-coating of the mixture of donor and acceptor materials, which usually leads to complicated dynamics and kinetics during the morphological evolution. [31,32] One of the long-standing challenges in realizing optimum BHJ configuration through such a method is to strike a delicate balance between the miscibility and self-organization of two active components during processing, thus imposing stringent requirements on the treatment conditions. Specifically, in the state-of-the-art nonfullerene systems, the donor and acceptor typically possess similar planar molecular structures and good miscibility, which enhances the difficulty in controlling the BHJ morphology. [33] An alternative way is to deposit neat donor and acceptor sequentially trying to reduce the complexity of interaction between two components. Previous studies have indicated that this sequential deposition method is feasible to create a p-in like structure due to the interdiffusion of top layer into bottom one and higher gradient concentration of acceptors near the cathode and donors near the anode. [34-36] Additionally, the two-step procedure allows each layer to be regulated and optimized independently, affording new opportunities for Bulk-heterojunction (BHJ) organic solar cells (OSCs) are prepared by a common one-step solution casting of donor-acceptor blends often encounter dynamic morphological evolution which is hard to control to achieve optimal performance. To overcome this hurdle, a generally applicable, sequential processing approach has been developed to construct high-performance OSCs without involving tedious processes. The morphology of photoactive layers comprising a polymer donor (PM6) and a nonfullerene acceptor (denoted as Y6-BO) can be precisely manipulated by tuning Y6-BO layer with a small amount of 1-chloronaphthalene additive to induce the structural order of Y6-BO molecules to impact the blend phase. Th...

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confidence: 99%

A Generally Applicable Approach Using Sequential Deposition to Enable Highly Efficient Organic Solar Cells

Gao

et al. 2020

Small Methods

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“…The E g is determined by the intersection point of absorption and emission spectra of the blends (Figure S11, Supporting Information), [58] and the E CT is obtained by fitting highly sensitive EQE (sEQE) and electroluminescence (EL) spectra (Figure 5b; Figure S12, Supporting Information). [56,59] The ternary cells exhibit a reduced charge extraction loss (E g -E CT ) of 0.078 eV b) The FF versus θ for the experimental data (colour symbols) and the simulation data (gray area) from the previous report. [31] c) Empirical relationship between the V oc and FF.…”

Section: Resultsmentioning

confidence: 92%

Exploring the Charge Dynamics and Energy Loss in Ternary Organic Solar Cells with a Fill Factor Exceeding 80%

Zeng

Xiao

et al. 2021

Advanced Energy Materials

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Ternary architecture is a promising strategy to enhance power conversion efficiencies (PCEs) of organic solar cells (OSCs). However, among all the photovoltaic parameters that govern the final PCEs, the fill factor (FF) for ternary OSCs is generally below 78%, limiting solar cells’ performance. Here, charge dynamics in the ternary cells PM6:DRTB‐T‐C4:Y6 with a FF of 80.88% and a PCE of 17.05% are thoroughly investigated by a series of transient characterization technologies, including transient absorption spectroscopy, transient photovoltage, and transient photocurrent measurements. The impressive FF results from effective exciton dissociation, enhanced charge transport and suppressed recombination in ternary cells. Moreover, the correlation between the measured FF and the charge recombination‐extraction competition is quantitatively analyzed by using a circuit model. The ternary cells also show small energy loss (Eloss). The findings here provide insight into achieving high‐FF and low‐Eloss ternary OSCs.

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“…Compared to the aggregation rate of BTP-eC9 in BHJ film, the acceptor in the G-BHJ film can be rapidly aggregated which is indicated by the sharp slope of the peak, almost three times faster than that in BHJ film. We hypothesize that the polymer layer could offer nuclei (or nucleation sites) for the small molecule layer in the G-BHJ process, which could induce the faster ordering of the small molecule layer 29 . It has revealed that the slow solidification leads to longer time for the active layer to aggregate and crystallize, giving oversized domain or excessive phase separation in the active layer 46 .…”

Section: Resultsmentioning

confidence: 99%

Graded bulk-heterojunction enables 17% binary organic solar cells via nonhalogenated open air coating

et al. 2021

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Graded bulk-heterojunction (G-BHJ) with well-defined vertical phase separation has potential to surpass classical BHJ in organic solar cells (OSCs). In this work, an effective G-BHJ strategy via nonhalogenated solvent sequential deposition is demonstrated using nonfullerene acceptor (NFA) OSCs. Spin-coated G-BHJ OSCs deliver an outstanding 17.48% power conversion efficiency (PCE). Depth-profiling X-ray photoelectron spectroscopy (DP-XPS) and angle-dependent grazing incidence X-ray diffraction (GI-XRD) techniques enable the visualization of polymer/NFA composition and crystallinity gradient distributions, which benefit charge transport, and enable outstanding thick OSC PCEs (16.25% for 300 nm, 14.37% for 500 nm), which are among the highest reported. Moreover, the nonhalogenated solvent enabled G-BHJ OSC via open-air blade coating and achieved a record 16.77% PCE. The blade-coated G-BHJ has drastically different D-A crystallization kinetics, which suppresses the excessive aggregation induced unfavorable phase separation in BHJ. All these make G-BHJ a feasible and promising strategy towards highly efficient, eco- and manufacture friendly OSCs.

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Achieving Balanced Crystallization Kinetics of Donor and Acceptor by Sequential‐Blade Coated Double Bulk Heterojunction Organic Solar Cells

Cited by 87 publications

References 65 publications

A Generally Applicable Approach Using Sequential Deposition to Enable Highly Efficient Organic Solar Cells

A Generally Applicable Approach Using Sequential Deposition to Enable Highly Efficient Organic Solar Cells

Exploring the Charge Dynamics and Energy Loss in Ternary Organic Solar Cells with a Fill Factor Exceeding 80%

Graded bulk-heterojunction enables 17% binary organic solar cells via nonhalogenated open air coating

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