Conjugated‐Polymer Blends for Organic Photovoltaics: Rational Control of Vertical Stratification for High Performance

Yu, Yan; Li, Xuan; Wang, Tao

doi:10.1002/adma.201601674

Cited by 116 publications

(107 citation statements)

References 154 publications

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“…While phase separation between the ED and EA materials was initially only considered in the horizontal direction of the active layer (in the plane parallel to the electrodes), with the development of new analytical techniques, probing the vertical ED–EA distribution has now become a common characterization in the field. These analytical techniques have been reviewed elsewhere and therefore, will not be presented here [14]. Various studies have confirmed that, in the pristine (as spun) state of BHJ active layers, a PC 61 BM-depleted layer is formed at the surface of the films; independently of the spin-coating speed [20,26,27,28].…”

Section: Generation Of Vertical Ed–ea Distribution In Single Activmentioning

confidence: 99%

“…It is worth mentioning here that this approach may not be used with all materials combination. A large number of interactions have to be taken into account to obtain the ideal vertical profiles in active layers for PSCs [14]. As we will discuss in the following section, minor chemical structure modifications of the active materials can have major effects on the formation of adequate vertical distributions.…”

Section: Generation Of Vertical Ed–ea Distribution In Single Activmentioning

confidence: 99%

“…The chemical nature of the active materials influences their interactions with each other, with the solvent used for active layer deposition and with the substrate on which they are deposited [14]. In fact, comparing results obtained using PCDTBT and its –OCH3 di-substituted derivative (PCDTBT1), one can already see the influence of small modifications on the vertical concentration gradients and the consequent effect on device performances [38,40].…”

Section: Generation Of Vertical Ed–ea Distribution In Single Activmentioning

confidence: 99%

“…In fact, both solution-processed small molecules and polymer solar cells (PSCs) now reach power conversion efficiencies (PCEs) over the milestone value of 10% [2,3,4,5,6,7,8,9]. Although these performances do not allow them to tackle the state-of-the-art silicon technologies yet, due to their low fabrication cost, lightweight and potential to be integrated into a variety of next-generation technologies such as wearable electronics or semi-transparent photovoltaic windows, PSCs have attracted great interest from the materials science community over the past decade [10,11,12,13,14]. The introduction and development of active layers composed of poly(3-hexylthiophene) (P3HT) and fullerene derivatives in the early 2000s is one of the first major achievements in the field as they led to a large increase in PCE over 6% [15,16].…”

Section: Introductionmentioning

confidence: 99%

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Fabrication Processes to Generate Concentration Gradients in Polymer Solar Cell Active Layers

Inaba

Vohra

2017

Materials

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Polymer solar cells (PSCs) are considered as one of the most promising low-cost alternatives for renewable energy production with devices now reaching power conversion efficiencies (PCEs) above the milestone value of 10%. These enhanced performances were achieved by developing new electron-donor (ED) and electron-acceptor (EA) materials as well as finding the adequate morphologies in either bulk heterojunction or sequentially deposited active layers. In particular, producing adequate vertical concentration gradients with higher concentrations of ED and EA close to the anode and cathode, respectively, results in an improved charge collection and consequently higher photovoltaic parameters such as the fill factor. In this review, we relate processes to generate active layers with ED–EA vertical concentration gradients. After summarizing the formation of such concentration gradients in single layer active layers through processes such as annealing or additives, we will verify that sequential deposition of multilayered active layers can be an efficient approach to remarkably increase the fill factor and PCE of PSCs. In fact, applying this challenging approach to fabricate inverted architecture PSCs has the potential to generate low-cost, high efficiency and stable devices, which may revolutionize worldwide energy demand and/or help develop next generation devices such as semi-transparent photovoltaic windows.

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Section: Generation Of Vertical Ed–ea Distribution In Single Activmentioning

confidence: 99%

Section: Generation Of Vertical Ed–ea Distribution In Single Activmentioning

confidence: 99%

Section: Generation Of Vertical Ed–ea Distribution In Single Activmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Fabrication Processes to Generate Concentration Gradients in Polymer Solar Cell Active Layers

Inaba

Vohra

2017

Materials

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“…Up to the present, most of the morphological observations of the CBLs used in inverted PSCs were largely observed without coverage of the active layer, using surface‐sensitive imaging tools such as atomic force microscopy (AFM) and scanning electron microscopy . In a few cases, destructive probing with X‐ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) were employed to reveal the depth‐dependent atomic ratios of the CBLs covered with PSC active layers, via depleting the above active layer as a function of film bombardment time . The thus measured atomic ratios across the unevenly destroyed PSC film with XPS or SIMS, however, provide little nanostructural features of the CBLs …”

Section: Introductionmentioning

confidence: 99%

Directed Vertical Diffusion of Photovoltaic Active Layer Components into Porous ZnO‐Based Cathode Buffer Layers

Kang

Yang

Lan

et al. 2018

Small

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Cathode buffer layers (CBLs) can effectively further the efficiency of polymer solar cells (PSCs), after optimization of the active layer. Hidden between the active layer and cathode of the inverted PSC device configuration is the critical yet often unattended vertical diffusion of the active layer components across CBL. Here, a novel methodology of contrast variation with neutron and anomalous X-ray reflectivity to map the multicomponent depth compositions of inverted PSCs, covering from the active layer surface down to the bottom of the ZnO-based CBL, is developed. Uniquely revealed for a high-performance model PSC are the often overlooked porosity distributions of the ZnO-based CBL and the differential diffusions of the polymer PTB7-Th and fullerene derivative PC BM of the active layer into the CBL. Interface modification of the ZnO-based CBL with fullerene derivative PCBEOH for size-selective nanochannels can selectively improve the diffusion of PC BM more than that of the polymer. The deeper penetration of PC BM establishes a gradient distribution of fullerene derivatives over the ZnO/PCBE-OH CBL, resulting in markedly improved electron mobility and device efficiency of the inverted PSC. The result suggests a new CBL design concept of progressive matching of the conduction bands.

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Contrasting Effects of Energy Transfer in Determining Efficiency Improvements in Ternary Polymer Solar Cells

Gong

et al. 2017

Adv Funct Materials

Self Cite

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Crystallizable, high-mobility conjugated polymers have been employed as secondary donor materials in ternary polymer solar cells in order to improve device efficiency by broadening their spectral response range and enhancing charge dissociation and transport. Here, contrasting effects of two crystallizable polymers, namely, PffBT4T-2OD and PDPP2TBT, in determining the efficiency improvements in PTB7-Th:PC 71 BM host blends are demonstrated. A notable power conversion efficiency of 11% can be obtained by introducing 10% PffBT4T-2OD (relative to PTB7-Th), while the efficiency of PDPP2TBT-incorporated ternary devices decreases dramatically despite an enhancement in hole mobility and light absorption. Blend morphology studies suggest that both PffBT4T-2OD and PDPP2TBT are well dissolved within the host PTB7-Th phase and facilitate an increased degree of phase separation between polymer and fullerene domains. While negligible charge transfer is determined in binary blends of each polymer mixture, effective energy transfer is identified from PffBT4T-2OD to PTB7-Th that contributes to an improvement in ternary blend device efficiency. In contrast, energy transfer from PTB7-Th to PDPP2TBT worsens the efficiency of the ternary device due to inefficient charge dissociation between PDPP2TBT and PC 71 BM. and acceptors, [1,2] controlling and optimizing the nanoscale morphology, [3][4][5] and via interfacial engineering of the device architectures. [6,7] Power conversation efficiency (PCE) metrics for this technology now stand at 13% for lab-scale single junction and tandem devices. [8,9] Ternary photovoltaic blends, [10][11][12][13][14][15] prepared by incorporating a third component into the donor:acceptor active layer, have emerged as a promising strategy for realizing further improvements in PCE by enhancing device spectral response and charge collection efficiency. This method is favorable as it removes the time-consuming and expensive process of synthesizing new conjugated polymers, in addition to the complicated manufacturing steps that are associated with tandem solar cell fabrication. [16,17] Recent work has shown that semicrystalline conjugated macromolecules or small molecules are effective third components when preparing efficient ternary solar cells. [18][19][20] For example, both the crystallinity and face-on preferential polymer orientation in PTB7-Th:PC 71 BM binary blends can be simultaneously enhanced via the addition of a highly crystalline small molecule p-DTS(FBTTH 2 ) 2 , resulting in a high PCE of 10.5% (a relative improvement of 14%). [21] Elsewhere, the incorporation of Si-PCDTBT into the PTB7:PC 71 BM system can result in high device fill factors (FF; up to 77%) through a significant reduction in charge recombination within the active layer. [22] Although these crystallizable additives can be highly ordered in relatively simple pure and binary systems, their ability to undergo ordering in ternary blends is not always realized. [23] Their exact location within the ternary blend morphology-and the cor...

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Conjugated‐Polymer Blends for Organic Photovoltaics: Rational Control of Vertical Stratification for High Performance

Cited by 116 publications

References 154 publications

Fabrication Processes to Generate Concentration Gradients in Polymer Solar Cell Active Layers

Fabrication Processes to Generate Concentration Gradients in Polymer Solar Cell Active Layers

Directed Vertical Diffusion of Photovoltaic Active Layer Components into Porous ZnO‐Based Cathode Buffer Layers

Contrasting Effects of Energy Transfer in Determining Efficiency Improvements in Ternary Polymer Solar Cells

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