Elevated Photovoltaic Performance in Medium Bandgap Copolymers Composed of Indacenodi-thieno[3,2-b]thiophene and Benzothiadiazole Subunits by Modulating the π-Bridge

Two random conjugated polymers (CPs), namely, PIDTT-TBT and PIDTT-TFBT, in which indacenodithieno[3,2-b]thiophene (IDTT), 3-octylthiophene, and benzothiadiazole (BT) were in turn utilized as electron-donor (D), π-bridge, and electron-acceptor (A) units, were synthesized to comprehensively analyze the impact of reducing thiophene π-bridge and further fluorination on photostability and photovoltaic performance. Meanwhile, the control polymer PIDTT-DTBT with alternating structure was also prepared for comparison. The broadened and enhanced absorption, down-shifted highest occupied molecular orbital energy level (EHOMO), more planar molecular geometry thus enhanced the aggregation in the film state, but insignificant impact on aggregation in solution and photostability were found after both reducing thiophene π-bridge in PIDTT-TBT and further fluorination in PIDTT-TFBT. Consequently, PIDTT-TBT-based device showed 185% increased PCE of 5.84% profited by synergistically elevated VOC, JSC, and FF than those of its counterpart PIDTT-DTBT, and this improvement was chiefly ascribed to the improved absorption, deepened EHOMO, raised μh and more balanced μh/μe, and optimized morphology of photoactive layer. However, the dropped PCE was observed after further fluorination in PIDTT-TFBT, which was mainly restricted by undesired morphology for photoactive layer as a result of strong aggregation even if in the condition of the upshifted VOC. Our preliminary results can demonstrate that modulating the π-bridge in polymer backbone was an effective method with the aim to enhance the performance for solar cell.

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Enhanced Photovoltaic Performance in D-π-A Copolymers Containing Triisopropylsilylethynyl-Substituted Dithienobenzodithiophene by Modulating the Electron-Deficient Units

Polymers ◽

10.3390/polym11010012 ◽

2018 ◽

Vol 11 (1) ◽

pp. 12 ◽

Cited By ~ 14

Author(s):

Junfeng Tong ◽

Lili An ◽

Jie Lv ◽

Pengzhi Guo ◽

Xunchang Wang ◽

...

Keyword(s):

Polymer Solar Cells ◽

Short Circuit ◽

Photovoltaic Performance ◽

Short Circuit Current ◽

Short Circuit Current Density ◽

Open Circuit ◽

Orbital Energy ◽

Polymer Backbone ◽

Blend Films ◽

The Impact

Three alternated D-π-A type 5,10-bis(triisopropylsilylethynyl)dithieno[2,3-d:2′,3′-d′]-benzo[1,2-b:4,5-b′]dithiophene (DTBDT-TIPS)-based semiconducting conjugated copolymers (CPs), PDTBDT-TIPS-DTBT-OD, PDTBDT-TIPS-DTFBT-OD, and PDTBDT-TIPS-DTNT-OD, bearing different A units, including benzothiadiazole (BT), 5,6-difluorinated-BT (FBT) and naphtho[1,2-c:5,6-c′]-bis[1,2,5]thiadiazole (NT), were designed and synthesized to investigate the impact of the variation in electron-deficient units on the properties of these photovoltaic polymers. It was exhibited that the down-shifted highest occupied molecular orbital energy level (EHOMO), the enhanced aggregation in both the chlorobenzene solution and the solid film, as well as the better molecular planarity, were achieved using methods involving fluorination and the replacement of BT with NT on the polymer backbone. The absorption profile was little changed upon fluorination; however, it was greatly broadened during replacement of BT with NT. Consequently, the optimized photovoltaic device based on the PDTBDT-TIPS-DTNT-OD exhibited synchronous enhancements in the open-circuit voltage (VOC) of 0.88 V, the short-circuit current density (JSC) of 7.21 mA cm−2, and the fill factor (FF) of 52.99%, resulting in a drastic elevation in the PCE by 129% to 3.37% compared to that of the PDTBDT-TIPS-DTBT-OD. This was triggered by PDTBDT-TIPS-DTNT-OD’s broadened absorption, deepened EHOMO, improved coplanarity, and enhanced SCLC mobility (which increased 3.9 times), as well as a favorable morphology of the active layer. Unfortunately, the corresponding PCE deteriorated after incorporating fluorine into the BT, due to the oversized aggregation and large phase separation morphology in the blend films, severely impairing its JSC. Our preliminary results demonstrated that the replacement of BT with NT in a D-π-A type polymer backbone was an effective strategy of tuning the molecular structure to achieve highly efficient polymer solar cells (PSCs).

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Fluorination Effect for Highly Conjugated Alternating Copolymers Involving Thienylenevinylene-Thiophene-Flanked Benzodithiophene and Benzothiadiazole Subunits in Photovoltaic Application

Polymers ◽

10.3390/polym12030504 ◽

2020 ◽

Vol 12 (3) ◽

pp. 504 ◽

Cited By ~ 1

Author(s):

Lili An ◽

Yubo Huang ◽

Xu Wang ◽

Zezhou Liang ◽

Jianfeng Li ◽

...

Keyword(s):

Thermal Stability ◽

Photovoltaic Performance ◽

Orbital Energy ◽

Optoelectronic Property ◽

Polymer Backbone ◽

Dissociation Probability ◽

Solid Film ◽

Microstructural Morphology ◽

Donor Acceptor ◽

The Impact

Two two-dimensional (2D) donor–acceptor (D-A) type conjugated polymers (CPs), namely, PBDT-TVT-BT and PBDT-TVT-FBT, in which two ((E)-(4,5-didecylthien-2-yl)vinyl)- 5-thien-2-yl (TVT) side chains were introduced into 4,8-position of benzo[1,2-b:4,5-bʹ]dithiophene (BDT) to synthesize the highly conjugated electron-donating building block BDT-TVT, and benzothiadiazole (BT) and/or 5,6-difluoro-BT as electron-accepting unit, were designed to systematically ascertain the impact of fluorination on thermal stability, optoelectronic property, and photovoltaic performance. Both resultant copolymers exhibited the lower bandgap (1.60 ~ 1.69 eV) and deeper highest occupied molecular orbital energy level (EHOMO, –5.17 ~ –5.37 eV). It was found that the narrowed absorption, deepened EHOMO and weakened aggregation in solid film but had insignificant influence on thermal stability after fluorination in PBDT-TVT-FBT. Accordingly, a PBDT-TVT-FBT-based device yielded 16% increased power conversion efficiency (PCE) from 4.50% to 5.22%, benefited from synergistically elevated VOC, JSC, and FF, which was mainly originated from deepened EHOMO, increased μh, μe, and more balanced μh/μe ratio, higher exciton dissociation probability and improved microstructural morphology of the photoactive layer as a result of incorporating fluorine into the polymer backbone.

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Molecular orbital energy level modulation through incorporation of selenium and fluorine into conjugated polymers for organic photovoltaic cells

Journal of Materials Chemistry A ◽

10.1039/c3ta13040a ◽

2013 ◽

Vol 1 (43) ◽

pp. 13422 ◽

Cited By ~ 26

Author(s):

Wenliu Zhuang ◽

Hongyu Zhen ◽

Renee Kroon ◽

Zheng Tang ◽

Stefan Hellström ◽

...

Keyword(s):

Energy Level ◽

Conjugated Polymers ◽

Molecular Orbital ◽

Photovoltaic Cells ◽

Organic Photovoltaic ◽

Orbital Energy ◽

Organic Photovoltaic Cells ◽

Molecular Orbital Energy ◽

Orbital Energy Level

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Effect of the highest occupied molecular orbital energy level offset on organic heterojunction photovoltaic cells

Applied Physics Letters ◽

10.1063/1.3491214 ◽

2010 ◽

Vol 97 (14) ◽

pp. 143503 ◽

Cited By ~ 37

Author(s):

Minlu Zhang ◽

Hui Wang ◽

C. W. Tang

Keyword(s):

Energy Level ◽

Molecular Orbital ◽

Photovoltaic Cells ◽

Orbital Energy ◽

Molecular Orbital Energy ◽

Highest Occupied Molecular Orbital ◽

Orbital Energy Level

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Synthesis and Photovoltaic Effect of Electron-Withdrawing Units for Low Band Gap Conjugated Polymers Bearing Bi(thienylenevinylene) Side Chains

Polymers ◽

10.3390/polym11091461 ◽

2019 ◽

Vol 11 (9) ◽

pp. 1461 ◽

Cited By ~ 2

Author(s):

Jianfeng Li ◽

Yufei Wang ◽

Ningning Wang ◽

Zezhou Liang ◽

Xu Wang ◽

...

Keyword(s):

Conjugated Polymers ◽

Open Circuit Voltage ◽

Photovoltaic Effect ◽

Photovoltaic Performance ◽

Hole Mobility ◽

Open Circuit ◽

Photovoltaic Devices ◽

Good Thermal Stability ◽

Highest Occupied Molecular Orbital ◽

Donor Acceptor

A novel (E)-5-(2-(5-alkylthiothiophen-2-yl)vinyl)thien-2-yl (TVT)-comprising benzo[1,2-b:4,5-b’]dithiophene (BDT) derivative (BDT-TVT) was designed and synthetized to compose two donor-acceptor (D-A) typed copolymers (PBDT-TVT-ID and PBDT-TVT-DTNT) with the electron-withdrawing unit isoindigo (ID) and naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole (NT), respectively. PBDT-TVT-ID and PBDT-TVT-DTNT showed good thermal stability (360 °C), an absorption spectrum from 300 nm to 760 nm and a relatively low lying energy level of Highest Occupied Molecular Orbital (EHOMO) (−5.36 to –5.45 eV), which could obtain a large open-circuit voltage (Voc) from photovoltaic devices with PBDT-TVT-ID or PBDT-TVT-DTNT. The photovoltaic devices with ITO/PFN/polymers: PC71BM/MoO3/Ag structure were assembled and exhibited a good photovoltaic performance with a power conversion efficiency (PCE) of 4.09% (PBDT-TVT-ID) and 5.44% (PBDT-TVT-DTNT), respectively. The best PCE of a PBDT-TVT-DTNT/PC71BM-based device mainly originated from its wider absorption, higher hole mobility and favorable photoactive layer morphology.

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Influence of the highest occupied molecular orbital energy level of the donor material on the effectiveness of the anode buffer layer in organic solar cells

physica status solidi (a) ◽

10.1002/pssa.201127047 ◽

2011 ◽

Vol 208 (8) ◽

pp. 1989-1994 ◽

Cited By ~ 16

Author(s):

J. C. Bernède ◽

L. Cattin ◽

S. Ouro Djobo ◽

M. Morsli ◽

S. R. B. Kanth ◽

...

Keyword(s):

Solar Cells ◽

Energy Level ◽

Buffer Layer ◽

Molecular Orbital ◽

Organic Solar Cells ◽

Orbital Energy ◽

Donor Material ◽

Highest Occupied Molecular Orbital ◽

Anode Buffer Layer ◽

Orbital Energy Level

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Conjugated Polymers Based on Benzo[2,1-b:3,4-b′]dithiophene with Low-Lying Highest Occupied Molecular Orbital Energy Levels for Organic Photovoltaics

ACS Applied Materials & Interfaces ◽

10.1021/am900327n ◽

2009 ◽

Vol 1 (7) ◽

pp. 1613-1621 ◽

Cited By ~ 31

Author(s):

Shengqiang Xiao ◽

Andrew C. Stuart ◽

Shubin Liu ◽

Wei You

Keyword(s):

Conjugated Polymers ◽

Molecular Orbital ◽

Organic Photovoltaics ◽

Energy Levels ◽

Orbital Energy ◽

Molecular Orbital Energy ◽

Highest Occupied Molecular Orbital

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Indeno[1,2-b]fluorene-based novel donor–acceptor conjugated copolymers

High Performance Polymers ◽

10.1177/0954008316688247 ◽

2017 ◽

Vol 30 (2) ◽

pp. 192-201 ◽

Cited By ~ 3

Author(s):

Ying Sun ◽

Xiaojing Ding ◽

Xueqin Zhang ◽

Qizan Huang ◽

Baoping Lin ◽

...

Keyword(s):

Photovoltaic Performance ◽

Hole Mobility ◽

Molecular Geometry ◽

Strong Electron ◽

Photovoltaic Properties ◽

Polymer Backbone ◽

Photovoltaic Efficiency ◽

Donor Acceptor ◽

Electron Deficiency ◽

Conjugated Copolymers

A series of conjugated copolymers based on indeno[1,2-b]fluorene as donor unit with different acceptor units have been synthesized to explore the influences of molecular backbone planarization and acceptor electronegativity on charge transport and photovoltaic properties. Polymer incorporating 2,3-diphenylquinoxaline acceptor moiety shows poor light-harvesting capacity and inferior photovoltaic efficiency of 0.5% due to twisted geometry. By introducing the stronger acceptor thiadiazolo[3,4-c]pyridine in polymer, intramolecular charge transfer is enhanced, giving rise to improved absorption property and photovoltaic efficiency of 1.39%. However, the polymer backbone is still twisted. When thiophene-flanked diketopyrrolopyrrole (DPP) is incorporated as electron acceptor, the polymer exhibits a more planar molecular geometry, yielding a broader and red-shifted absorption spectrum as well as a significantly improved hole mobility of 1.46E-2 cm2 V−1 s−1. However, the photovoltaic device efficiency is only enhanced to be 1.69%. The low-lying lowest unoccupied molecular orbital of −3.95 eV as a result of the strong electron deficiency of the DPP unit may lead to the inefficient charge dissociation and increase the charge recombination, which may give rise to the limit photovoltaic performance.

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Carbon Nanotube-Induced Planarization of Conjugated Polymers in Solution

MRS Proceedings ◽

10.1557/proc-858-hh12.4 ◽

2004 ◽

Vol 858 ◽

Cited By ~ 1

Author(s):

Jian Chen ◽

Rajagopal Ramasubramaniam ◽

Haiying Liu

Keyword(s):

Carbon Nanotubes ◽

Carbon Nanotube ◽

Conjugated Polymers ◽

Spectroscopic Study ◽

Surface Quality ◽

Hybrid Materials ◽

Conjugated Polymer ◽

Visible Absorption ◽

The Impact ◽

Conformational Interaction

ABSTRACTThe understanding of the conformational interaction between conjugated polymers and carbon nanotubes in solution is essential to develop the applications of carbon nanotubes, particularly conjugated polymer-carbon nanotube hybrid materials. The visible absorption spectroscopic study shows that curved carbon nanotube surfaces can induce the planarization of individual conjugated polymers such as poly(p-phenyleneethynylene)s and poly(3-alkylthiophene)s in solution. The impact of nanotube surface quality on the interaction between carbon nanotubes and conjugated polymers is investigated.

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