Reducing Trap‐Assisted Recombination in Small Organic Molecule‐Based Photovoltaics by the Addition of a Conjugated Block Copolymer

Cho, Kyuwan; Kim, Jinseck; Yoon, So Yeon; Ryu, Ka Yeon; Jang, Song Rim; Lim, Bogyu; Kim, Kyungkon

doi:10.1002/marc.201700630

Cited by 18 publications

(10 citation statements)

References 23 publications

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“…Additionally, certain of these photogenerated carriers return to the ground state through monomolecular trap‐assisted recombination, interfacial recombination, and surface trap‐assisted recombination, and the carriers subsequently weaken the device performance because the reduction of current and internal potential occurs via a nonradiative relaxation process . Therefore, it is necessary to enhance the carrier transport properties to improve the performance of OSCs.…”

Section: Introductionmentioning

confidence: 99%

Vertical Phase Separation for Highly Efficient Organic Solar Cells Incorporating Conjugated‐Polyelectrolytes

Han

Choi

Lee

et al. 2018

Adv Materials Inter

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OSCs can be applied to various fields due to their many advantages, such as high performance, low cost, flexibility, and potential for modulation. Recently, the research on OSCs has been focused on materials with high-performance organic donors and acceptors (fullerene and nonfullerene) and device structure research, such as ternary structure and tandem structure. These studies have contributed to developing high-performance OSCs with excellent power conversion efficiency (PCE) over 14% in single cells and 17.3% in tandem structure cells. [1][2][3][4][5][6][7][8][9][10] OSCs are based on an active layer that has a bulk-heterojunction (BHJ) structure that consists of an organic donor and acceptor, and OSCs generate excitons within the range of their optical properties. Additionally, OSCs show photovoltaic properties via the process of charge disassociation and charge transport. [11,12] Due to the limitation of the optical properties of organic donors and acceptors, carrier mobility and carrier balance are critical factors that determine the performance of OSCs. [13][14][15][16] Therefore, photogenerated carriers that have been generated in a BHJ have the disadvantage of exhibiting a lower mobility compared with inorganic semiconductor-based solar cells because of the organic semiconductor's inherent properties, such as monomolecular recombination and bimolecular recombination. [17][18][19] Additionally, certain of these photogenerated carriers return to the ground state through monomolecular trap-assisted recombination, [20][21][22] interfacial recombination, [23][24][25] and surface trap-assisted recombination, [26] and the carriers subsequently weaken the device performance because the reduction of current and internal potential occurs via a nonradiative relaxation process. [27,28] Therefore, it is necessary to enhance the carrier transport properties to improve the performance of OSCs.Recent research has reported important device structure modifications to improve the carrier transport properties of OSCs. Specifically, the carrier mobility can be increased by introducing a buffer layer through enhancing carrier transport, and the device performance can be enhanced by reducing the recombination. Hybrid organic solar cells are made through a simple one-pot coating process with conjugated polyelectrolytes (CPEs), poly[9,9-bis(4′sulfonatobutyl)fluorenealt-thiophene-doped (PFT-D). The hybrid active layer incorporated with PFT-D shows vertical phase separation by selfassembled properties of PFT-D, which result from a molecular dipole between the conjugated backbone and the side chain. The hybrid activelayer with PFT-D shows that homogeneous morphology, surface potential properties, and hydrophobic surface properties favor for enhancing photovoltaic performance. These results are identified by contact angle characteristics, X-ray photoelectron spectroscopy (XPS) profiling, and X-ray diffraction (XRD), atomic force measurement (AFM), and electrostatic force measurement (EFM) analyses. With fullerene based hybrid active...

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Section: Introductionmentioning

confidence: 99%

Vertical Phase Separation for Highly Efficient Organic Solar Cells Incorporating Conjugated‐Polyelectrolytes

Han

Choi

Lee

et al. 2018

Adv Materials Inter

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“…When the slope tends to kT / q , the mechanism of charge recombination will be dominated by bimolecular recombination. Otherwise, when the slope is far away from kT / q , the trap-assisted recombination will gradually dominate . The slopes of the PBDB-T:2T2CSi-4F and PBDB-T:4T2CSi-4F devices are determined to be 1.01 and 1.06 kT / q , respectively.…”

Section: Resultsmentioning

confidence: 98%

Nonfused Ring Electron Acceptors for Efficient Organic Solar Cells Enabled by Multiple Intramolecular Conformational Locks

Zhong

Cui

Zhu

et al. 2022

ACS Appl. Energy Mater.

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Nonfused ring electron acceptors (NFREAs) have become a research hotspot of organic solar cells (OSCs) due to their facile synthesis. However, efficient NFREAs not only need to maintain the advantages of FREAs but also need to optimize the molecular structure of the conjugate backbone to achieve good planarity. Therefore, choosing the appropriate building blocks is a prerequisite for achieving efficient OSCs. Here, two simple NFREAs 2T2CSi-4F and 4T2CSi-4F, based on diester-thieno[3,2-b]thiophene (2T2C) as the central core unit and 4,4-di-2-ethylhexyl-dithieno[3,2-b:2′,3′-d]silole (DTSi) or thieno[3,2-b]thiophene (TT) as the conjugated linking unit, were designed and synthesized. The density function theory results manifest that the oxygen atom of the thiophene ester group can form O···S interaction with the sulfur atom. Introducing noncovalent interactions can form multiple intramolecular conformational locks, which greatly enhance the molecular planarity. In addition, 2T2CSi-4F with a symmetrical structure exhibits red-shifted absorption, shallower lowest unoccupied molecular orbital energy levels, and stronger crystallinity than 4T2CSi-4F. Therefore, the PBDB-T:2T2CSi-4F device with favorable molecular packing and morphology achieves a higher power conversion efficiency of 10.04%. Our work demonstrates that the 2T2C unit and multimolecular conformational lock strategy are conducive to the development of efficient NFREAs.

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“…The slope of 1.39 kT/q for the device with pure PEIE is bigger than that of 1.24 kT/q for the device with 1-LiCl-PEIE ( Figure 4 b) [ 25 ]. The result hints that the LiCl-based double layer can effectively suppress the trap-assisted recombination [ 26 ], suggesting further promoting the extraction of charge. The enhancement in the extraction of charge can be confirmed by the higher rectification ratio for the device with 1-LiCl-PEIE compared with the device with PEIE ( Figure 4 c).…”

Section: Resultsmentioning

confidence: 99%

Effective Double Electron Transport Layer Inducing Crystallization of Active Layer for Improving the Performance of Organic Solar Cells

Chen

et al. 2021

Nanomaterials

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Interface modification plays an important role in enhancing the photoelectric conversion efficiency and stability of organic solar cells. In this work, alkali metal lithium chloride (LiCl) was introduced between indium tin oxide and polyethyleneimine ethoxylate (PEIE) to prepare a double-layer electron transport layer. Results show that the introduction of LiCl has dual functions. The first function is that LiCl can enhance conductivity, thereby facilitating charge collection. The second function is that the double-layer electron transport layer based on LiCl can induce the crystallization of active layer, thereby enhancing charge transport. Devices with LiCl/PEIE double layer achieve a high power conversion efficiency (PCE) of 3.84%, which is 21.5% higher than that of pristine devices (the PCE of pristine devices with pure PEIE interface layer is 3.16%).

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Reducing Trap‐Assisted Recombination in Small Organic Molecule‐Based Photovoltaics by the Addition of a Conjugated Block Copolymer

Cited by 18 publications

References 23 publications

Vertical Phase Separation for Highly Efficient Organic Solar Cells Incorporating Conjugated‐Polyelectrolytes

Vertical Phase Separation for Highly Efficient Organic Solar Cells Incorporating Conjugated‐Polyelectrolytes

Nonfused Ring Electron Acceptors for Efficient Organic Solar Cells Enabled by Multiple Intramolecular Conformational Locks

Effective Double Electron Transport Layer Inducing Crystallization of Active Layer for Improving the Performance of Organic Solar Cells

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