Query: A high dielectric constant non-fullerene acceptor for efficient bulk-heterojunction organic solar cells

Candidate papers:

abstract: The majority of organic semiconductors have a low relative dielectric constant (er 6) has attracted a very limited attention. Moreover, high performance OSCs based on high dielectric constant photovoltaic materials are still in their infancy. Herein, we report an oligoethylene oxide side chain containing non fullerene acceptor (ITIC OE) with a high relative dielectric constant of er 9.4, which is two times larger than that of its alkyl chain containing counterpart ITIC. Encouragingly, the OSCs based on ITIC OE show a high power conversion efficiency of 8.5% which is the highest value for OSCs that employ high dielectric constant materials. Nevertheless, this value is lower than those of ITIC based control devices. The less phase separated morphology in blend films due to the reduced crystallinity of ITIC OE and the too good miscibility between PBDB T and ITIC OE are responsible for the lower device performance. This work suggests additional prerequisites to make high dielectric constants play a significant role in OSCs.
author_names: Xi Liu

Boming Xie

Chunhui Duan

Zhaojing Wang

Baobing Fan

Kai Zhang

Baojun Lin

Fallon J M Colberts

Wei Ma

Raj Rene Janssen

Fei Huang

Yong Cao
title: A high dielectric constant non fullerene acceptor for efficient bulk heterojunction organic solar cells
year: 2018

abstract: An all carbon non fullerene electron acceptor material based on diindeno[1,2 g:1',2' s]rubicene (DIR) was readily synthesized and processed for bulk heterojunction organic solar cells. High PCE up to 3.05% with a relatively high VOC of 1.22 V has been achieved with P3HT electron donor material by the variation of donor acceptor blending ratio.
author_names: Hung-Yang Chen

Jan Golder

Shih-Chieh Yeh

Chiao-Wen Lin

Chao-Tsen Chen

Chin-Ti Chen
title: Diindeno[1,2 g:1',2' s]rubicene: all carbon non fullerene electron acceptor for efficient bulk heterojunction organic solar cells with high open circuit voltage
year: 2015

abstract: Abstract Fluorination of molecular donors and acceptors enables an effective tuning of the energetics in organic bulk heterojunctions, leading to enhanced power conversion efficiencies in organic solar cells with non fullerene acceptors. To date, the impacts of fluorination on the dielectric properties and the key processes of charge dissociation and recombination are still poorly understood. Based on the fluorinated PBDBT 2F donor and IT 4F acceptor with a favorably enhanced dielectric constant in the blend films, we explore key factors attributing to the realized high fill factor (0.745) and efficiency (13.4% in the solar cells. Through comparing the IT 4F solar cell to that with non fluorinated ITIC acceptor, we identify distinct recombination profiles in the IT 4F based device that exhibits a highly efficient charge dissociation together with a small reduction factor (3.71 x10 2) for bi molecular recombination and a low recombination coefficient of 2.404 x 10 13 cm 3 s 1. These particularities lead to an ultrafast carrier sweepout
author_names: Xuning Zhang

Dongyang Zhang

Qian Zhou

Rong Wang

Jiyu Zhou

Jianqiu Wang

Huiqiong Zhou

Yuan Zhang
title: Fluorination with an enlarged dielectric constant prompts charge separation and reduces bimolecular recombination in non fullerene organic solar cells with a high fill factor and efficiency 13%
venue: Nano Energy
year: 2019

abstract: Interlayers and interface engineering plays a pivotal role in achieving efficient charge extraction necessary for realizing high power conversion efficiency (PCE) in bulk heterojunction organic solar cells. In this study, we report a novel strategy of combining advantages of both fullerene derivative and non fullerene acceptor materials by employing solution processable non fullerene acceptor 3,9 bis(2 methylene (3 (1,1 dicyanomethylene) indan one) 5,5,11,11 tetrakis(4 hexylphenyl) dithieno[2,3 d:2',3' d' s indaceno[1,2 b:5,6 b']dithiophene (ITIC) to modify the interface between ZnO based electron transport layer and poly[4,8 bis(5 (2 ethylhexyl)thiophen 2 yl) benzo [1,2 b;4,5 b' dithiophe ne 2,6 diyl alt (4 (2 ethylhexyl) 3 fluorothieno[3,4 b]thiophene 2 carb oxylate 2 6 diyl) (PTB7 Th) phenyl C71 butyric acid methyl ester based photoactive layer. An improvement in PCE from 7.5% to 9% has been achieved for the devices with ITIC modified interlayer. Time resolved photoluminescence (PL) via time correlated single photon counting and photo electrochemical impedance spectroscopy (photo EIS) measurements were carried out to investigate the causes for improved PCE for the devices with ITIC modified interlayer.
author_names: Kunal Borse

Ramakant Sharma

Dipti Gupta

Aswani Yella
title: High Efficiency Organic Solar Cells With Solution Processable Non Fullerene Acceptor as an Interlayer
venue: IEEE Journal of Photovoltaics
year: 2019

abstract: A significant leap in record breaking power conversion efficiencies (PCEs) of single junction bulk heterojunction (BHJ) organic solar cells (OSCs) to over 18%[1] has recently been achieved. This can be credited to the rapid developments of new non fullerene acceptors (NFAs) paired with suitable high performing polymer donors. While these breakthroughs are encouraging, it remains crucial to attain a deeper and more comprehensive understanding of the underlying mechanisms governing these novel and high performing polymer:NFA systems. Several recent studies have attributed the high performances of NFA based solar cells to an improvement in the open circuit voltage (VOC) without significantly diminishing the charge generation efficiency.[2 4] Particularly, in polymer:NFA systems, high VOC values have been achieved with efficient charge generation regardless of a very small energetic driving force for Even though significant breakthroughs with over 18% power conversion efficiencies (PCEs) in polymer:non fullerene acceptor (NFA) bulk heterojunction organic solar cells (OSCs) have been achieved, not many studies have focused on acquiring a comprehensive understanding of the underlying mechanisms governing these systems. This is because it can be challenging to delineate device photophysics in polymer:NFA blends comprehensively, and even more complicated to trace the origins of the differences in device photophysics to the subtle differences in energetics and morphology. Here, a systematic study of a series of polymer:NFA blends is conducted to unify and correlate the cumulative effects of i) voltage losses, ii) charge generation efficiencies, iii) non geminate recombination and extraction dynamics, and iv) nuanced morphological differences with device performances. Most importantly, a deconvolution of the major loss processes in polymer:NFA blends and their connections to the complex BHJ morphology and energetics are established. An extension to advanced morphological techniques, such as solid state NMR (for atomic level insights on the local ordering and donor:acceptor pp interactions) and resonant soft X ray scattering (for donor and acceptor interfacial area and domain spacings) provide detailed insights on how efficient charge generation, transport, and extraction processes can outweigh increased voltage losses to yield high PCEs.
author_names: Akchheta Karki

Joachim Vollbrecht

Alexander J Gillett

Philipp Selter

Jaewon Lee

Zhengxing Peng

Nora Schopp

Alana L Dixon

Max Schrock

Vojtech Nadazdy

Franz Schauer

Harald W Ade

Bradley F Chmelka

Guillermo C Bazan

Richard H Friend

Thuc-Quyen Nguyen
title: Unifying Charge Generation, Recombination, and Extraction in Low Offset Non Fullerene Acceptor Organic Solar Cells
year: 2020

abstract: In bulk heterojunction (BHJ) organic solar cells (OSCs) both the electron affinity (EA) and ionization energy (IE) offsets at the donor acceptor interface should equally control exciton dissociation. Here, we demonstrate that in low bandgap non fullerene acceptor (NFA) BHJs ultrafast donor to acceptor energy transfer precedes hole transfer from the acceptor to the donor and thus renders the EA offset virtually unimportant. Moreover, sizeable bulk IE offsets of about 0.5 eV are needed for efficient charge transfer and high internal quantum efficiencies, since energy level bending at the donor NFA interface caused by the acceptors' quadrupole moments prevents efficient exciton to charge transfer state conversion at low IE offsets. The same bending, however, is the origin of the barrier less charge transfer state to free charge conversion. Our results provide a comprehensive picture of the photophysics of NFA based blends, and show that sizeable bulk IE offsets are essential to design efficient BHJ OSCs based on low bandgap NFAs. A systematic analysis of a series of donor acceptor organic blends shows that in solar cells based on low bandgap non fullerene acceptors an ionization energy offset of about 0.5 eV is required to ensure efficient charge separation.
author_names: Safakath Karuthedath

Julien Gorenflot

Yuliar Firdaus

Neha Chaturvedi

Catherine S P De Castro

George T Harrison

Jafar Iqbal Khan

Anastasia A Markina

Ahmed Hesham Balawi

Top Archie Dela Pena

Wenlan Liu

Ru-Ze Liang

Anirudh Sharma

Sri H K Paleti

Weimin Zhang

Yuanbao Lin

Erkki Alarousu

Dalaver Hussain Anjum

Pierre M Beaujuge

Stefaan De Wolf

Iain McCulloch

Thomas D Anthopoulos

Derya Baran

Denis Andrienko

Frederic Laquai
title: Intrinsic efficiency limits in low bandgap non fullerene acceptor organic solar cells
venue: Nature Materials
year: 2020

abstract: Organic solar cells are currently experiencing a second golden age thanks to the development of novel non fullerene acceptors (NFAs) Surprisingly, some of these blends exhibit high efficiencies despite a low energy offset at the heterojunction. Herein, free charge generation in the high performance blend of the donor polymer PM6 with the NFA Y6 is thoroughly investigated as a function of internal field, temperature and excitation energy. Results show that photocurrent generation is essentially barrierless with near unity efficiency, regardless of excitation energy. Efficient charge separation is maintained over a wide temperature range, down to 100 K, despite the small driving force for charge generation. Studies on a blend with a low concentration of the NFA, measurements of the energetic disorder, and theoretical modeling suggest that CT state dissociation is assisted by the electrostatic interfacial field which for Y6 is large enough to compensate the Coulomb dissociation barrier.
author_names: Lorena Perdigon-Toro

Huotian Zhang

Anastasia A Markina

Jun Yuan

Seyed Mehrdad Hosseini

Christian M Wolff

Guangzheng Zuo

Martin Stolterfoht

Yingping Zou

Feng Gao

Denis Andrienko

Safa Shoaee

Dieter Neher
title: Barrierless Free Charge Generation in the High Performance PM6:Y6 Bulk Heterojunction Non Fullerene Solar Cell.
venue: Advanced materials
year: 2020

abstract: Non fullerene acceptors (NFAs) have recently outperformed their fullerene counterparts in binary bulk heterojunction (BHJ) organic solar cells (OSCs) Further development of NFA OSCs may benefit other novel OSC device structures that alter or extend the standard BHJ concept. Here, we report such a new processing route that forms a BHJ like morphology between sequentially processed polymer donor and NFA with high power conversion efficiencies in excess of 10% Both devices show similar charge generation and recombination behaviours, supporting formation of similar BHJ active layers. We correlate the ~30 meV smaller open circuit voltage in sq BHJ devices to more substantial non radiative recombination by voltage loss analysis. We also determine the exciton diffusion length of benchmark polymer PBDB T to be 10 3 nm. Our results demonstrate high efficiency OSC devices using sequential deposition method and provide new opportunities to further improve performance of state of the art OSCs.
author_names: Jiangbin Zhang

Bin Kan

Andrew J Pearson

Andrew J Parnell

Joshaniel F K Cooper

Xiao-Ke Liu

Patrick J Conaghan

Thomas R Hopper

Yutian Wu

Xiangjian Wan

Feng Gao

Neil C Greenham

Artem A Bakulin

Yongsheng Chen

Richard H Friend
title: Efficient non fullerene organic solar cells employing sequentially deposited donor acceptor layers
year: 2018

abstract: A solution processable, non fullerene electron acceptor, 2,2' (5,5 dioctyl 5 H dibenzo[b,d]silole 3,7 diyl)bis(thiophene 5,2 diyl))bis(methanylylidene))bis(1 H indene 1,3(2 H) dione) (called N5) comprised of dibenzosilole and 1,3 indanedione building blocks was designed, synthesized, and fully characterized. N5 is highly soluble in various organic solvents, has high thermal stability, and has energy levels matching those of archetypal donor poly(3 hexylthiophene) Solution processable, bulk heterojunction solar cells afforded promising power conversion efficiency of 2.76 when N5 was used as a non fullerene electron acceptor along with the conventional donor polymer poly(3 hexylthiophene) As per our knowledge, the material reported herein is the first example in the literature where synchronous use of such building blocks is demonstrated in the design an efficient, non fullerene acceptor.
author_names: Hemlata Patil

Akhil Gupta

Ben Alford

Di Ma

Steven H Priver

Ante Bilic

Prashant Sonar

Sheshanath V Bhosale
title: Conjoint use of Dibenzosilole and Indan 1,3 dione Functionalities to Prepare an Efficient Non Fullerene Acceptor for Solution Processable Bulk Heterojunction Solar Cells
year: 2015

abstract: Non fullerene acceptors have recently attracted tremendous interest because of their potential as alternatives to fullerene derivatives in bulk heterojunction organic solar cells. However, the power conversion efficiencies (PCEs) have lagged far behind those of the polymer/fullerene system, mainly because of the low fill factor (FF) and photocurrent. Here we report a novel perylene bisimide (PBI) acceptor, SdiPBI Se, in which selenium atoms were introduced into the perylene core. With a well established wide band gap polymer (PDBT T1) as the donor, a high efficiency of 8.4% with an unprecedented high FF of 70.2% is achieved for solution processed non fullerene organic solar cells. Efficient photon absorption, high and balanced charge carrier mobility, and ultrafast charge generation processes in PDBT T1:SdiPBI Se films account for the high photovoltaic performance. Our results suggest that non fullerene acceptors have enormous potential to rival or even surpass the performance of their fullerene counterparts.
author_names: Dong Meng

Dan Zi Sun

Chengmei Zhong

Tao Liu

Bingbing Fan

Lijun Huo

Yan-ping Li

Wei Jiang

Hyosung Choi

Taehyo Kim

Jin Kyun Kim

Yanming Sun

Zhaohui Wang

Alan J Heeger
title: High Performance Solution Processed Non Fullerene Organic Solar Cells Based on Selenophene Containing Perylene Bisimide Acceptor.
venue: Journal of the American Chemical Society
year: 2016