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Journal articleCui J, Daboczi M, Regue M, et al., 2022,
2D Bismuthene as a Functional Interlayer between BiVO4 and NiFeOOH for Enhanced Oxygen-Evolution Photoanodes
, ADVANCED FUNCTIONAL MATERIALS, Vol: 32, ISSN: 1616-301X -
Journal articleLabanti C, Wu J, Shin J, et al., 2022,
Light-intensity-dependent photoresponse time of organic photodetectors and its molecular origin
, NATURE COMMUNICATIONS, Vol: 13- Author Web Link
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- Citations: 2
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Journal articleLuke J, Yang EJ, Chin Y-C, et al., 2022,
Strong Intermolecular Interactions Induced by High Quadrupole Moments Enable Excellent Photostability of Non-Fullerene Acceptors for Organic Photovoltaics
, ADVANCED ENERGY MATERIALS, Vol: 12, ISSN: 1614-6832 -
Journal articleYan H, Wade J, Wan L, et al., 2022,
Enhancing hole carrier injection via low electrochemical doping on circularly polarized polymer light-emitting diodes
, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 10, Pages: 9512-9520, ISSN: 2050-7526 -
Journal articleTan E, Kim J, Stewart K, et al., 2022,
The Role of Long-Alkyl-Group Spacers in Glycolated Copolymers for High-Performance Organic Electrochemical Transistors
, ADVANCED MATERIALS, Vol: 34, ISSN: 0935-9648 -
Journal articleHamilton I, Suh M, Bailey J, et al., 2022,
Optimizing Interfacial Energetics for Conjugated Polyelectrolyte Electron Injection Layers in High Efficiency and Fast Responding Polymer Light Emitting Diodes
, ACS APPLIED MATERIALS & INTERFACES, ISSN: 1944-8244 -
Journal articleLee J, Luke J, Ahn H, et al., 2022,
Efficient Charge Transport Driven by Strong Intermolecular Interactions in Cyclopentadithiophene-Based Donor-Acceptor Type Conjugated Copolymers
, ADVANCED ELECTRONIC MATERIALS, Vol: 8, ISSN: 2199-160X -
Journal articleWang B, Nam S, Limbu S, et al., 2022,
Properties and Applications of Copper(I) Thiocyanate Hole-Transport Interlayers Processed from Different Solvents
, ADVANCED ELECTRONIC MATERIALS, Vol: 8, ISSN: 2199-160X -
Journal articleLee HKH, Stewart K, Hughes D, et al., 2022,
Proton radiation hardness of organic photovltaics: an in-depth study
, Solar RRL, ISSN: 2367-198XRecent developments of solution-processed bulk-heterojunction organic photovoltaic (OPV) cells have demonstrated power conversion efficiencies (PCEs) as high as 18% for single-junction devices. Such a high PCE in addition to its desirable lightweight property and high mechanical flexibility can realize high specific power and small stowed volume, which are key considerations when choosing PV for space missions. To take one important step forward, their resilience to ionizing radiation should be well studied. Herein, the effect of proton irradiation at various fluences on the performance of benchmark OPV cells is explored under AM0 illumination. The remaining device performance is found to decrease with increasing proton fluence, which correlates to changes in electrical and chemical properties of the active layer. By redissolving the devices, the solubility of the active layer is found to decrease with increasing proton fluence, suggesting that the active materials are likely cross-linked. Additionally, Raman studies reveal conformational changes of the polymer leading to a higher degree of energetic disorder. Despite a drop in performance, the retaining percentage of the performance is indeed higher than the current market-dominating space PV technology—III–V semiconductor-based PV, demonstrating a high potential of the OPV cell as a candidate for space applications
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Journal articleYan H, Tseng T-W, Omagari S, et al., 2022,
Dynamic molecular conformational change leading to energy transfer in F8-5% BSP copolymer revealed by single-molecule spectroscopy
, JOURNAL OF CHEMICAL PHYSICS, Vol: 156, ISSN: 0021-9606- Author Web Link
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- Citations: 2
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Journal articleMarin-Beloqui J, Zhang G, Guo J, et al., 2022,
Insight into the Origin of Trapping in Polymer/Fullerene Blends with a Systematic Alteration of the Fullerene to Higher Adducts
, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 126, Pages: 2708-2719, ISSN: 1932-7447 -
Journal articlePark SY, Labanti C, Luke J, et al., 2022,
Organic bilayer photovoltaics for efficient indoor light harvesting
, Advanced Energy Materials, Vol: 12, Pages: 1-10, ISSN: 1614-6832Indoor organic photovoltaics (OPVs) are a potential niche application for organic semiconductors due to their strong and well-matched absorption with the emission of indoor lighting. However, due to extremely low photocurrent generation, the device parameters critical for efficient indoor OPVs differ from those under 1 Sun conditions. Herein, these critical device parameters—recombination loss and shunt resistance (Rsh)—are identified and it is demonstrated that bilayer OPVs are suitable for indoor PV applications. Compared to bulk-heterojunction (BHJ), the open-circuit voltage loss of bilayer devices under low light intensities is much smaller, consistent with a larger surface photovoltage response, indicating suppressed recombination losses. The bilayer devices show a higher fill factor at low light intensities, resulting from high Rsh afforded by the ideal interfacial contacts between the photoactive and the charge transport layers. The high Rsh enables bilayer devices to perform well without a light-soaking process. Finally, the charge carriers are extracted rapidly in bilayers, which are attributed to strongly suppressed trap states possibly induced by isolated domains and non-ideal interfacial contacts in BHJs. This study highlights the excellent suitability of bilayer OPVs for indoor applications and demonstrates the importance of device architecture and interfacial structures for efficient indoor OPVs.
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Journal articleChin Y-C, Daboczi M, Henderson C, et al., 2022,
Suppressing PEDOT:PSS doping-induced interfacial recombination loss in perovskite solar cells
, ACS Energy Letters, Vol: 7, Pages: 560-568, ISSN: 2380-8195PEDOT:PSS is widely used as a hole transport layer (HTL) in perovskite solar cells (PSCs) due to its facile processability, industrial scalability, and commercialization potential. However, PSCs utilizing PEDOT:PSS suffer from strong recombination losses compared to other organic HTLs. This results in lower open-circuit voltage (VOC) and power conversion efficiency (PCE). Most studies focus on doping PEDOT:PSS to improve charge extraction, but it has been suggested that a high doping level can cause strong recombination losses. Herein, we systematically dedope PEDOT:PSS with aqueous NaOH, raising its Fermi level by up to 500 meV, and optimize its layer thickness in p-i-n devices. A significant reduction of recombination losses at the dedoped PEDOT:PSS/perovskite interface is evidenced by a longer photoluminescence lifetime and higher magnitude of surface photovoltage, leading to an increased device VOC, fill factor, and PCE. These results provide insights into the relationship between doping level of HTLs and interfacial charge carrier recombination losses.
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Journal articleDaboczi M, Ratnasingham SR, Mohan L, et al., 2021,
Optimal Interfacial Band Bending Achieved by Fine Energy Level Tuning in Mixed-Halide Perovskite Solar Cells
, ACS ENERGY LETTERS, Vol: 6, Pages: 3970-3981, ISSN: 2380-8195- Author Web Link
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- Citations: 3
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Journal articleMohan L, Ratnasingham SR, Panidi J, et al., 2021,
Determining out-of-plane hole mobility in CuSCN via the time-of-flight technique to elucidate its function in perovskite solar cells
, ACS Applied Materials and Interfaces, Vol: 13, Pages: 38499-38507, ISSN: 1944-8244Copper(I) thiocyanate (CuSCN) is a stable, low-cost, solution-processable p-type inorganic semiconductor used in numerous optoelectronic applications. Here, for the first time, we employ the time-of-flight (ToF) technique to measure the out-of-plane hole mobility of CuSCN films, enabled by the deposition of 4 μm-thick films using aerosol-assisted chemical vapor deposition (AACVD). A hole mobility of ∼10–3 cm2/V s was measured with a weak electric field dependence of 0.005 cm/V1/2. Additionally, by measuring several 1.5 μm CuSCN films, we show that the mobility is independent of thickness. To further validate the suitability of our AACVD-prepared 1.5 μm-thick CuSCN film in device applications, we demonstrate its incorporation as a hole transport layer (HTL) in methylammonium lead iodide (MAPbI3) perovskite solar cells (PSCs). Our AACVD films result in devices with measured power conversion efficiencies of 10.4%, which compares favorably with devices prepared using spin-coated CuSCN HTLs (12.6%), despite the AACVD HTLs being an order of magnitude thicker than their spin-coated analogues. Improved reproducibility and decreased hysteresis were observed, owing to a combination of excellent film quality, high charge-carrier mobility, and favorable interface energetics. In addition to providing a fundamental insight into charge-carrier mobility in CuSCN, our work highlights the AACVD methodology as a scalable, versatile tool suitable for film deposition for use in optoelectronic devices.
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Journal articleVasilopoulou M, bin Mohd Yusoff AR, Daboczi M, et al., 2021,
High efficiency blue organic light-emitting diodes with below-bandgap electroluminescence
, NATURE COMMUNICATIONS, Vol: 12, ISSN: 2041-1723- Author Web Link
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- Citations: 24
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Journal articleClarke AJ, Luke J, Meitzner R, et al., 2021,
Non-fullerene acceptor photostability and its impact on organic solar cell lifetime
, CELL REPORTS PHYSICAL SCIENCE, Vol: 2- Author Web Link
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- Citations: 13
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Journal articleLee TH, Park W-W, Park SY, et al., 2021,
Planar Organic Bilayer Heterojunctions Fabricated on Water with Ultrafast Donor-to-Acceptor Charge Transfer
, SOLAR RRL, Vol: 5, ISSN: 2367-198X- Author Web Link
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- Citations: 4
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Journal articleMarin-Beloqui JM, Toolan DTW, Panjwani NA, et al., 2021,
Triplet-Charge Annihilation in a Small Molecule Donor: Acceptor Blend as a Major Loss Mechanism in Organic Photovoltaics
, ADVANCED ENERGY MATERIALS, Vol: 11, ISSN: 1614-6832- Author Web Link
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- Citations: 6
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Journal articleLimbu S, Stewart K, Nightingale J, et al., 2021,
Solid-State Ionic Liquid: Key to Efficient Detection and Discrimination in Organic Semiconductor Gas Sensors
, ACS APPLIED ELECTRONIC MATERIALS, Vol: 3, Pages: 2152-2163- Author Web Link
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- Citations: 1
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Journal articleKyeong M, Lee J, Daboczi M, et al., 2021,
Organic cathode interfacial materials for non-fullerene organic solar cells
, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 9, Pages: 13506-13514, ISSN: 2050-7488- Author Web Link
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- Citations: 11
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Journal articleYun D-J, Lee S, Kim SH, et al., 2021,
Bevel Structure Based XPS Analysis as a Non-Destructive Chemical Probe for Complex Interfacial Structures of Organic Semiconductors
, SMALL METHODS, Vol: 5, ISSN: 2366-9608 -
Journal articlePark J-M, Lee TH, Kim DW, et al., 2021,
Designing a naphthyridinedione-based conjugated polymer for thickness-tolerant high efficiency polymer solar cells
, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 9, Pages: 10846-10854, ISSN: 2050-7488- Author Web Link
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- Citations: 4
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Journal articleLabanti C, Sung MJ, Luke J, et al., 2021,
Selenium-substituted non-fullerene acceptors: a route to superior Operational stability for organic bulk heterojunction solar cells.
, ACS Nano, Vol: 15, Pages: 7700-7712, ISSN: 1936-0851Non-fullerene acceptors (NFAs) for organic solar cells (OSCs) have significantly developed over the past five years with continuous improvements in efficiency now over 18%. However, a key challenge still remains in order to fully realize their commercialization potential: the need to extend device lifetime and to control degradation mechanisms. Herein, we investigate the effect of two different molecular engineering routes on the widely utilized ITIC NFA, to tune its optoelectronic properties and interactions with the donor polymer in photoactive blends. Heavier selenium (Se) atoms substitute sulfur (S) atoms in the NFA core in either outer or inner positions, and methyl chains are attached to the end groups. By investigating the effects of these structural modifications on the long-term operational stability of bulk-heterojunction OSC devices, we identify outer selenation as a powerful strategy to significantly increase device lifetime compared to ITIC. Combining outer selenation and methylation results in an impressive 95% of the initial OSC efficiency being retained after 450 h under operating conditions, with an exceptionally long projected half-lifetime of 5600 h compared to 400 h for ITIC. We find that the heavier and larger Se atoms at outer-core positions rigidify the molecular structure to form highly crystalline films with low conformational energetic disorder. It further enhances charge delocalization over the molecule, promoting strong intermolecular interactions among acceptor molecules. Upon methylation, this strong intermolecular interaction stabilizes acceptor domains in blends to be resilient to light-induced morphological changes, thereby leading to superior device stability. Our results highlight the crucial role of NFA molecular structure for OSC operational stability and provide important NFA design rules via heteroatom position and end-group control.
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Journal articleKafourou P, Park B, Luke J, et al., 2021,
One‐step sixfold cyanation of benzothiadiazole acceptor units for air‐stable high‐performance n‐type organic field‐effect transistors
, Angewandte Chemie, Vol: 133, Pages: 6035-6042, ISSN: 0044-8249Reported here is a new high electron affinity acceptor end group for organic semiconductors, 2,1,3‐benzothiadiazole‐4,5,6‐tricarbonitrile (TCNBT). An n‐type organic semiconductor with an indacenodithiophene (IDT) core and TCNBT end groups was synthesized by a sixfold nucleophilic substitution with cyanide on a fluorinated precursor, itself prepared by a direct arylation approach. This one‐step chemical modification significantly impacted the molecular properties: the fluorinated precursor, TFBT IDT, a poor ambipolar semiconductor, was converted into TCNBT IDT, a good n‐type semiconductor. The electron‐deficient end group TCNBT dramatically decreased the energy of the highest occupied and lowest unoccupied molecular orbitals (HOMO/LUMO) compared to the fluorinated analogue and improved the molecular orientation when utilized in n‐type organic field‐effect transistors (OFETs). Solution‐processed OFETs based on TCNBT IDT exhibited a charge‐carrier mobility of up to μe≈0.15 cm2 V−1 s−1 with excellent ambient stability for 100 hours, highlighting the benefits of the cyanated end group and the synthetic approach.
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Journal articleHeeney M, Kafourou P, Park B, et al., 2021,
One-step six-fold cyanation of benzothiadiazole acceptor Units for air-stable high-performance n-type organic field-effect transistors
, Angewandte Chemie International Edition, Vol: 60, Pages: 5970-5977, ISSN: 1433-7851We report a new high electron affinity acceptor end group for organic semiconductors, 2,1,3-benzothiadiazole-4,5,6-tricarbonitrile (TCNBT). An n-type organic semiconductor with an indacenodithiophene (IDT) core and TCNBT end groups was synthesized by a six-fold nucleophilic substitution with cyanides on a fluorinated precursor, itself prepared by a direct arylation approach. This one-step chemical modification was found to significantly impact the molecular properties: the fluorinated precursor, TFBT IDT, a poor ambipolar semiconductor, was converted into TCNBT IDT, a good n-type semiconductor. The highly electron-deficient end group TCNBT dramatically decreased the energy of the highest occupied and lowest unoccupied molecular orbitals (HOMO/LUMO) compared to the fluorinated analogue and improved the molecular orientation when utilized in n-type organic field-effect transistors (OFETs). Solution-processed OFETs based on TCNBT IDT exhibited a charge carrier mobility of up to µ e ≈ 0.15 cm 2 V -1 s -1 with excellent ambient stability for 100 hours, highlighting the benefits of the cyanated end group and the synthetic approach.
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Journal articlePark SY, Chandrabose S, Price MB, et al., 2021,
Photophysical pathways in efficient bilayer organic solar cells: The importance of interlayer energy transfer
, NANO ENERGY, Vol: 84, ISSN: 2211-2855- Author Web Link
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- Citations: 17
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Journal articleRatnasingham SR, Mohan L, Daboczi M, et al., 2021,
Novel scalable aerosol-assisted CVD route for perovskite solar cells
, Materials Advances, Vol: 2, Pages: 1606-1612Organo-metal halide perovskite research has progressed rapidly, with photovoltaic (PV) devices achieving over 25% power conversion efficiency (PCE). However, scalable production of these devices is an ongoing challenge. We demonstrate the growth of methylammonium lead triiodide (MAPI) films via a novel two-step aerosol-assisted chemical vapour deposition (AACVD) method leading to the first ever perovskite-based PV devices using active layers deposited by AACVD. This is a scalable deposition process, requiring less complex equipment than conventional CVD. Furthermore, our method utilises methanol (MeOH) as the only solvent, as opposed to harmful solvents typically used in perovskite processing. Structural and optical characterization confirms successful formation of MAPI with no secondary phases and an optical bandgap of ∼1.58 eV. The final film had large grains (order of μm), with thickness ranging from 500–1100 nm. These films were used to fabricate working PV devices resulting in a champion PCE of 5.4%. While films demonstrated high structural and compositonal quality, we identified large film roughness as a limiting factor in device PCE, and elucidate the origin of this via detailed study of the film growth, which reveals a unique multi-step film formation process.
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Journal articleYiwen W, Jinho L, Xueyan H, et al., 2021,
Recent progress and Challenges toward highly stable nonfullerene acceptor‐based organic solar cells
, Advanced Energy Materials, Vol: 11, ISSN: 1614-6832Organic solar cells (OSCs) based on nonfullerene acceptors (NFAs) have made significant breakthrough in their device performance, now achieving a power conversion efficiency of ≈18% for single junction devices, driven by the rapid development in their molecular design and device engineering in recent years. However, achieving long‐term stability remains a major challenge to overcome for their commercialization, due in large part to the current lack of understanding of their degradation mechanisms as well as the design rules for enhancing their stability. In this review, the recent progress in understanding the degradation mechanisms and enhancing the stability of high performance NFA‐based OSCs is a specific focus. First, an overview of the recent advances in the molecular design and device engineering of several classes of high performance NFA‐based OSCs for various targeted applications is provided, before presenting a critical review of the different degradation mechanisms identified through photochemical‐, photo‐, and morphological degradation pathways. Potential strategies to address these degradation mechanisms for further stability enhancement, from molecular design, interfacial engineering, and morphology control perspectives, are also discussed. Finally, an outlook is given highlighting the remaining key challenges toward achieving the long‐term stability of NFA‐OSCs.
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Journal articleLimbu S, Park K-B, Wu J, et al., 2021,
Identifying the Molecular Origins of High-Performance in Organic Photodetectors Based on Highly Intermixed Bulk Heterojunction Blends
, ACS NANO, Vol: 15, Pages: 1217-1228, ISSN: 1936-0851- Author Web Link
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- Citations: 13
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