A Highly Efficient Non‐Fullerene Organic Solar Cell with a Fill Factor over 0.80 Enabled by a Fine‐Tuned Hole‐Transporting Layer

Zheng, Zhong; Hu, Qin; Zhang, Shaoqing; Zhang, Dongyang; Wang, Jianqiu; Xie, Shenkun; Wang, Rong; Qin, Yunpeng; Li, Wanning; Lei, Hong; Liang, Ningning; Liu, Feng; Zhang, Yuan; Wei, Zhixiang; Tang, Zhiyong; Russell, Thomas P.; Hou, Jianhui; Zhou, Huiqiong

doi:10.1002/adma.201801801

Cited by 378 publications

(288 citation statements)

References 46 publications

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cathode interlayer materials that are successfully used in the efficient OSCs, anode interlayer (AIL) materials with satisfactory performances are rather rare. [18][19][20][21] At present, the lack of ideal AILs has seriously impeded the pace toward practical application of OSCs.Currently, the enhancement of work function (WF) is the most critical issue for the development of AILs. [18][19][20][21] At present, the lack of ideal AILs has seriously impeded the pace toward practical application of OSCs.

Currently, the enhancement of work function (WF) is the most critical issue for the development of AILs.

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confidence: 99%

Significant Effect of Fluorination on Simultaneously Improving Work Function and Transparency of Anode Interlayer for Organic Solar Cells

Lü

Liao

et al. 2019

Advanced Energy Materials

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cathode interlayer materials that are successfully used in the efficient OSCs, anode interlayer (AIL) materials with satisfactory performances are rather rare. [15][16][17] Although several materials such as poly (3,4-ethylenedioxythiophene):(styrene sulfonate) (PEDOT:PSS) and metal oxides have been widely used as AILs, the acidic nature of PEDOT:PSS and the energy-consuming preparation process of metal oxides limit their practical uses in OSCs. [18][19][20][21] At present, the lack of ideal AILs has seriously impeded the pace toward practical application of OSCs.Currently, the enhancement of work function (WF) is the most critical issue for the development of AILs. [22,23] Many research results indicated that WFs have significant influence on the open-circuit voltage (V oc ) of the devices. [24,25] For instance, Vasilopoulou et al. enhanced the WF of molybdenum oxide AILs from 5.4 to 5.9 eV by controlling the hydrogenation degree of Mo element, by which the V oc of the device increased from 0.59 to 0.65 V. [26] Moreover, Irwin et al. prepared a NiO x AIL with a high WF of 5.4 eV, and achieved a V oc increment of 14 mV for the device. [27] However, in recent years, with the situation that the highest occupied molecular orbital (HOMO) levels of donors in fullerenefree devices are constantly downshifted for achieving high V oc , [28,29] most previously developed AILs cannot satisfy the new demands for modifying efficient OSCs because the low WFs of these materials give rise to large energy offsets with donors, which causes interfacial barrier for hole collection and leads to serious V oc loss. [30] Thus, it is particularly urgent to explore new approaches that can further enhance the WF of AILs.Among various materials, conjugated polyelectrolytes (CPEs) are promising candidates as AIL materials due to their neutral pH, excellent charge transporting capacity, and good filmforming property. [31,32] Unlike PEDOT:PSS and metal oxides, the chemical structure of CPEs can be readily modified through synthetic chemistry, which provides great opportunities for improving the WF of AILs. For example, Lee et al. enhanced the WF of p-PFP-X from 4.97 to 5.26 eV by tuning electric dipoles of the cation-anion pairs on the side chains of CPEs, and obtained an increased PCE of 9.2% in the OSC device. [33] However, these methods merely achieved limited WF enhancement and most of the developed AILs only worked well in fullerene-based OSCs. [34] Moreover, protonic acid doping has Since the highest occupied molecular orbital (HOMO) level of donors in organic solar cells (OSCs) is being constantly downshifted for achieving high open-circuit voltage (V oc ), a further enhancement of the anode work function (WF) is required. Herein, an effective approach of fluorinationis demonstrated to simultaneously improve the WF and transparency for anode interlayer (AIL) material. By fluorination, in combination with the dialysis treatment in LiCl solution, the WF of PCP-2F-Li could be significantly enhanced from 4.86 to 5.0 eV, as compared to PCP-Na...

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Currently, the enhancement of work function (WF) is the most critical issue for the development of AILs.

…”

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confidence: 99%

Significant Effect of Fluorination on Simultaneously Improving Work Function and Transparency of Anode Interlayer for Organic Solar Cells

Lü

Liao

et al. 2019

Advanced Energy Materials

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“…in single-layer solar cells, [19][20][21] demonstrating unprecedented potentials of nonfullerene acceptors for enabling high-performance photovoltaic devices for practical applications. [22,23] Along with the advancement of novel FREAs, developing appropriate donor polymers having good compatibility with acceptor materials is equally critical for attaining highperformance nonfullerene PSCs.…”

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“…Additionally, the FMO energy levels of the polymer donors should be appropriately aligned in order to match well with those of the FREAs for implementing efficient exciton dissociation and minimizing photon energy loss (E loss = E g − eV oc ) in the corresponding devices. [19,26,27] With these considerations, a plenty of donor polymers have been designed and synthesized to match with the new emerging FREAs, showing promising device performances in nonfullerene PSCs. [19,26,27] With these considerations, a plenty of donor polymers have been designed and synthesized to match with the new emerging FREAs, showing promising device performances in nonfullerene PSCs.…”

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confidence: 99%

“…[19,20,[28][29][30][31][32][33][34][35][36][37][38][39][40] To the best of our knowledge, all these high-performance donor polymers are alternating donor-acceptor (D-A) type copolymers, which are exclusively based on benzo[1,2-b:4,5-b′]dithiophene (BDT) donor unit [41] copolymerized with a few acceptor counits, such as 5,6-difluoro-2-alkyl-2H-benzo[d] [1,2,3]triazole (FTAZ), [42] benzo[1,2-c:4,5-c′]-dithiophene-4,8-dione (BDD) [43] etc. [19,20,[28][29][30][31][32][33][34][35][36][37][38][39][40] To the best of our knowledge, all these high-performance donor polymers are alternating donor-acceptor (D-A) type copolymers, which are exclusively based on benzo[1,2-b:4,5-b′]dithiophene (BDT) donor unit [41] copolymerized with a few acceptor counits, such as 5,6-difluoro-2-alkyl-2H-benzo[d] [1,2,3]triazole (FTAZ), [42] benzo[1,2-c:4,5-c′]-dithiophene-4,8-dione (BDD) [43] etc.…”

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Phthalimide‐Based High Mobility Polymer Semiconductors for Efficient Nonfullerene Solar Cells with Power Conversion Efficiencies over 13%

Chen

Koh

et al. 2018

Advanced Science

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Highly efficient nonfullerene polymer solar cells (PSCs) are developed based on two new phthalimide‐based polymers phthalimide‐difluorobenzothiadiazole (PhI‐ffBT) and fluorinated phthalimide‐ffBT (ffPhI‐ffBT). Compared to all high‐performance polymers reported, which are exclusively based on benzo[1,2‐b:4,5‐b′]dithiophene (BDT), both PhI‐ffBT and ffPhI‐ffBT are BDT‐free and feature a D‐A1‐D‐A2 type backbone. Incorporating a second acceptor unit difluorobenzothiadiazole leads to polymers with low‐lying highest occupied molecular orbital levels (≈−5.6 eV) and a complementary absorption with the narrow bandgap nonfullerene acceptor IT‐4F. Moreover, these BDT‐free polymers show substantially higher hole mobilities than BDT‐based polymers, which are beneficial to charge transport and extraction in solar cells. The PSCs containing difluorinated phthalimide‐based polymer ffPhI‐ffBT achieve a substantial PCE of 12.74% and a large V oc of 0.94 V, and the PSCs containing phthalimide‐based polymer PhI‐ffBT show a further increased PCE of 13.31% with a higher J sc of 19.41 mA cm−2 and a larger fill factor of 0.76. The 13.31% PCE is the highest value except the widely studied BDT‐based polymers and is also the highest among all benzothiadiazole‐based polymers. The results demonstrate that phthalimides are excellent building blocks for enabling donor polymers with the state‐of‐the‐art performance in nonfullerene PSCs and the BDT is not necessary for constructing such donor polymers.

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“…In search of higher performances, interfacial engineering of such an anode interlayer (AIL)/cathode interlayer has led to a multitude of design approaches. There are a range of AIL designs with various considerations, including hole extraction layer (HEL), hole transport layer (HTL), and exciton dissociation layer (EDL), leading to cascading heterojunction (CHJ) designs . In addition, it is also well established that the underlying interlayer may influence the active material layer morphology and/or act as an exciton‐blocking layer (ExBL) .…”

Section: Introductionmentioning

confidence: 99%

Anode interlayer in organic photovoltaics: Narrow bandgap small molecular materials as exciton‐blocking layer

Golder

Lin

Chen

2019

J Chinese Chemical Soc

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Six materials were used as an interlayer at the anode side (anode interlayer [AIL]) of an archetypical planar heterojunction organic solar cell (OSC). In addition to two conventional wide bandgap hole transport materials (HTMs), tris(4‐carbazol‐9‐ylphenyl)amine (TCTA) and trans‐4,4′‐bis[N‐(naphthalen‐1‐yl)‐N‐phenylamino]stilbene (NPAE), we explore four narrow bandgap materials, bis(biphenylaminospiro)‐fumaronitrile (PhSPFN), bis(N‐(naphthalen‐1‐yl)‐N‐phenylamino)anthraquinone (NPAAnQ), bis‐(di(2‐fluorophenyl)aminospiro)‐fumaronitrile (FPhSPFN), and bis[4‐(N‐(pyren‐1‐yl)‐N‐phenylamino)phenyl]fumaronitrile (PyPAFN), the energy levels of which essentially align with the ones of SubPc, the active light‐absorbing material of the OSC study herein. By using a narrow bandgap AIL, universally enhanced short‐circuit current density and power conversion efficiencies (PCEs) have been achieved. In addition, one of these materials, FPhSPFN, results in a PCE of 5.13%, which is the highest reported value for SubPc solar cells with a similar architecture. This is ascribed to the formation of an otherwise passive exciton‐blocking interface. Furthermore, this demonstrates that charge selectivity by way of a high‐lying lowest unoccupied molecular orbital (LUMO) energy level is not a prerequisite for successful AIL design. As such, in terms of energy level alignment and bandgap energies, we establish a viable alternative approach toward interface and interlayer material design.

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A Highly Efficient Non‐Fullerene Organic Solar Cell with a Fill Factor over 0.80 Enabled by a Fine‐Tuned Hole‐Transporting Layer

Cited by 378 publications

References 46 publications

Significant Effect of Fluorination on Simultaneously Improving Work Function and Transparency of Anode Interlayer for Organic Solar Cells

Significant Effect of Fluorination on Simultaneously Improving Work Function and Transparency of Anode Interlayer for Organic Solar Cells

Phthalimide‐Based High Mobility Polymer Semiconductors for Efficient Nonfullerene Solar Cells with Power Conversion Efficiencies over 13%

Anode interlayer in organic photovoltaics: Narrow bandgap small molecular materials as exciton‐blocking layer

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