Small Molecule Near-Infrared Boron Dipyrromethene Donors for Organic Tandem Solar Cells

Li, Tianyi; Meyer, Toni; Ma, Zaifei; Benduhn, Johannes; Körner, Christian; Zeika, Olaf; Vandewal, Koen; Leo, Karl

doi:10.1021/jacs.7b07887

Cited by 82 publications

(57 citation statements)

References 22 publications

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Compared with traditional fullerene acceptors such as [6,6]-phenyl-C61/C71-butyric acid methyl ester (PC 61 BM/PC 71 BM), PSCs based on the n-OS acceptors have shown great potential in device performance and device stability. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Compared with traditional fullerene acceptors such as [6,6]-phenyl-C61/C71-butyric acid methyl ester (PC 61 BM/PC 71 BM), PSCs based on the n-OS acceptors have shown great potential in device performance and device stability.…”

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confidence: 99%

Side‐Chain Impact on Molecular Orientation of Organic Semiconductor Acceptors: High Performance Nonfullerene Polymer Solar Cells with Thick Active Layer over 400 nm

Luo

Sun

Chen

et al. 2018

Advanced Energy Materials

124

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In recent years, n-type organic semiconductor (n-OS) (or called as nonfullerene) acceptors have been gaining their popularity in low production cost, light weight, flexible and large-area applications in polymer solar cells (PSCs) due to their excellent optical absorption, tunable energy levels, facile synthesis, and good solution-processability. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Compared with traditional fullerene acceptors such as [6,6]-phenyl-C61/C71-butyric acid methyl ester (PC 61 BM/PC 71 BM), PSCs based on the n-OS acceptors have shown great potential in device performance and device stability. [14,[17][18][19][20][21][22][23][24][25][26][27][28][29] And the n-OS acceptors-based devices have achieved power conversion efficiency (PCE) as high as over 12%. [30][31][32][33][34][35][36][37][38][39][40][41][42] The rational design of the n-OS acceptors is typically based on molecular packing and orbital energetics strategies that are utilized to effectively alter the extension of π conjugation and frontier orbital energy levels. [43][44][45][46][47] Up to now, great efforts have been devoted to development of building blocks, terminal functional groups and side chains, which can effectively tune the band gap and energy levels of the n-OS acceptors. Among them, relatively little attention have been paid to the sidechain engineering of the n-OS acceptors. [5,[48][49][50][51] In comparison with backbone structure and terminal functional groups manipulation, "side-chain engineering" strategy can not only avoid the time-consuming end-capping deficient group and backbone synthesis, but also can improve the photovoltaic performance of PSCs. [33,49,[52][53][54] In addition, this strategy provides an intuitive approach to study the structure-property relationship for the acceptor with the small alterations of the side-chain structures. Structural modification in sidechains of the acceptor, such as changing in length, position, symmetry, and dimension, can remarkably affect molecular packing and intermolecular interaction. [5,[48][49][50][51] For example, the side-chain isomerization of ITIC (3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4hexylphenyl)-dithieno[2,3-d:2,3-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene) with meta-alkyl-phenyl instead of para-alkyl-phenyl led to the acceptor m-ITIC with more evident crystallinity and higher electron mobility; [48] the replacement of the side chains of rigid indacenodithieno[3,2-b]-thiophene (IDTT) core from 4-hexylphenyl to 5-hexylthienyl downshifts the lowest unoccupied molecular orbital (LUMO) energy levels and improves the A new n-type organic semiconductor (n-OS) acceptor IDTPC with n-hexyl side chains is developed. Compared to side chains with 4-hexylphenyl counterparts (IDTCN), such a design endows the acceptor of IDTPC with higher electron mobility, more ordered face-on molecular packing, and lower band gap. Therefore, the IDTPC-based polymer solar cells (PSCs) with a newly developed wide bandgap polymer PTQ10 as donor exhi...

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confidence: 99%

Side‐Chain Impact on Molecular Orientation of Organic Semiconductor Acceptors: High Performance Nonfullerene Polymer Solar Cells with Thick Active Layer over 400 nm

Luo

Sun

Chen

et al. 2018

Advanced Energy Materials

124

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“…Thermalization means hot charge carriers created upon photon absorption relax down to the conduction band of the photoactive materials . To overcome these losses, integrating several cells into stacked multijunction devices has been proposed and developed . By this approach, single‐junction devices having different absorption spectra are integrated as subcells, providing a broader absorption spectrum, as illustrated in Figure a.…”

Section: Optical In‐couplingmentioning

confidence: 99%

“…Moreover, the thermalization losses are lowered due to the usage of materials having different optical gaps and open‐circuit voltages. Li et al produced organic tandem solar cells with near infrared (NIR) absorbers (wavelength > 780 nm) and achieved a PCE of almost 10%. Two different “green” absorbing thiophene‐based donors and the NIR‐absorbing donor boron dipyrromethene (BODIPY) have been used to build tandem cells, as illustrated in Figure a.…”

Section: Optical In‐couplingmentioning

confidence: 99%

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Optical In‐Coupling in Organic Solar Cells

2018

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thus offering an environmentally friendly approach. Furthermore, the use of simple low-temperature processing techniques makes it a potentially low-cost technology. However, efficiency and stability are so far lacking, hampering the full exploitation of the potential this technology has in these new applications. After the demonstration of the first reasonably performing organic solar cell by Tang [1] achieving approximately 1% efficiency, much effort has been put into improving these values. Nowadays, efficiencies well beyond 10%, and even over 13% have been reached, [2,3] however, with hard-to-synthesize polymers that so far have not shown sufficient stability for practical applications.Closer to commercial exploitation, solar cells based on oligomers (also termed "small molecules") and the material class used by Tang et al. [1] are investigated and introduced in their pioneering papers. [4][5][6][7][8][9][10][11][12][13][14][15] This material class can be either deposited by vacuum evaporation or solution processing. [16][17][18][19][20][21] The advantage of vacuum evaporation is that very pure layers without solvent residuals are produced, which is favorable for a higher stability of the cells. Also, they allow several cells to be very easily integrated into stacked multijunction devices. [22] With multijunction cells, Heliatek has reached an efficiency of 13.2% using proprietary materials that allow long lifetimes and can be readily manufactured. [23] Single-junction devices with similar published materials achieve above 8% efficiency [24] and above 10% in single-junction and tandem devices, respectively. [25] While these values are much improved as compared to the pioneering work of Tang, there is still a large gap to be closed to reach efficiencies comparable to silicon solar cells and other inorganic PV technologies.Here, first we will address limitations of organic solar cells, such as short exciton diffusion length, voltage, and transport problems. After that, various approaches to solve these challenges will be introduced. These include the bulk heterojunction, multijunction devices, and periodically patterned structures on substrates or active layers. Among these approaches, we focus on optical in-coupling, which allows more photons to be funneled into the thin organic active layers, yielding higher efficiencies. Limitations of Organic Solar CellsAlthough organic solar cells have huge potential and acceptable power conversion efficiencies (PCEs), they still have limitations caused by a short exciton diffusion length, charge transport, and low open-circuit voltage (V oc ). In this section, we briefly summarize why OSCs lack in efficiency, and optical in-coupling is required to improve the performance.Organic photovoltaics have many unique properties, such as flexibility, transparency, and low weight, which allows novel applications to be addressed. A remaining challenge is to increase the power conversion efficiencies into the range that is offered by conventional inorganic photovoltaics. Due to the li...

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“…

Two aryl-fused BODIPY dyes BF-BDP and NF-BDP were synthesized with benzofuran and naphtho [b]furan fusions on the a,bpositions of the BODIPY skeleton, respectively, resulting in large linear conjugated structures. [3][4][5] On one hand, however, their relatively low lying emissive excited states allow more possible non-radiative decay routes, which limit the photoluminescent quantum yields (PLQY) of long-wavelength emission. Their emission bands were red-shifted to l = 730 and 760 nm in vacuum-deposited films.

Fluorophores with photoactivity in the deep-red to NIR region (> 650 nm) are of high interest for several applications, such as chemical sensor, [1] bio-imaging label, [2] and organic photovoltaics.

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confidence: 99%

Highly Efficient Deep‐Red‐ to Near‐Infrared‐Absorbing and Emissive Benzo/Naphtho[b]furan‐Fused Boron Dipyrromethene (BODIPY)

Qiao

et al. 2018

ChemPhotoChem

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Two aryl-fused BODIPY dyes BF-BDP and NF-BDP were synthesized with benzofuran and naphtho [b]furan fusions on the a,bpositions of the BODIPY skeleton, respectively, resulting in large linear conjugated structures. Both molecules were planar and were characterized as intense deep-red/NIR emitters with emission bands tunable by the solution concentration. Their emission bands were red-shifted to l = 730 and 760 nm in vacuum-deposited films.Fluorophores with photoactivity in the deep-red to NIR region (> 650 nm) are of high interest for several applications, such as chemical sensor, [1] bio-imaging label, [2] and organic photovoltaics. [3][4][5] On one hand, however, their relatively low lying emissive excited states allow more possible non-radiative decay routes, which limit the photoluminescent quantum yields (PLQY) of long-wavelength emission. One the other hand, interaction between photons and electrons that is the principle mechanism in all these applications, high stability and low photo-bleaching effect are required. Thus, continuous research efforts have been put into developing and characterizing new deep-red and NIR fluorophores.4,4-Difluoro-4-borata-3a,4a-diaza-s-indacene, abbreviated as BODIPY, is a popular family of dyes characterized by flexible chemical modifications, tunable absorption/emission band, good photo-stability and high fluorescent efficiency. [6,7] Since the typical photo-active region of a BODIPY chromophore is from 450 to 550 nm, several approaches have been realized to achieve deep-red and NIR absorbing/emitting BODIPYs: (1) introduce "push-pull" strategy by introducing electron donating/withdrawing groups; (2) replace meso-carbon atom by a nitrogen atom to obtain aza-BODIPY; (3) extend the p conjugation system by fusing the dipyrromethene core with aryl moieties. [8] Amongst all these methods, aromatic fusion is a promising strategy for the development of high quality emitters, because the extra rigidity provided by the aromatic fusion structure can enhance the thermal/photo-stability and suppress the non-radiative decay routes via the bond vibration and/or rotation. [9][10][11][12] Several recent examples of BODIPY with aromatic fusion along with either a,b-fusion or b-fusion strategy are illustrated in Scheme 1. [13][14][15][16][17][18] Such fused BODIPYs are generally obtained via complex reaction for aryl-fused pyrrole precursors and/or inter-/intra-molecular ring closure, which usually sacrifices the overall yields of the final BODIPYs.

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Small Molecule Near-Infrared Boron Dipyrromethene Donors for Organic Tandem Solar Cells

Cited by 82 publications

References 22 publications

Side‐Chain Impact on Molecular Orientation of Organic Semiconductor Acceptors: High Performance Nonfullerene Polymer Solar Cells with Thick Active Layer over 400 nm

Side‐Chain Impact on Molecular Orientation of Organic Semiconductor Acceptors: High Performance Nonfullerene Polymer Solar Cells with Thick Active Layer over 400 nm

Optical In‐Coupling in Organic Solar Cells

Highly Efficient Deep‐Red‐ to Near‐Infrared‐Absorbing and Emissive Benzo/Naphtho[b]furan‐Fused Boron Dipyrromethene (BODIPY)

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