Mohamad Insan Nugraha
@kaust.edu.sa
Physical Science and Engineering Division
King Abdullah University of Science and Technology (KAUST)
RESEARCH, TEACHING, or OTHER INTERESTS
Condensed Matter Physics, Materials Science, Electronic, Optical and Magnetic Materials, Renewable Energy, Sustainability and the Environment
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Zhaoheng Ling, Mohamad Insan Nugraha, Wisnu Tantyo Hadmojo, Yuanbao Lin, Sang Young Jeong, Emre Yengel, Hendrik Faber, Hua Tang, Frédéric Laquai, Abdul-Hamid Emwas,et al.
American Chemical Society (ACS)
Mohamad Insan Nugraha, Indriyati Indriyati, Indah Primadona, Murali Gedda, Gerald Ensang Timuda, Ferry Iskandar, and Thomas D. Anthopoulos
Wiley
AbstractSemiconducting colloidal quantum dots (CQDs) represent an emerging class of thermoelectric materials for use in a wide range of future applications. CQDs combine solution processability at low temperatures with the potential for upscalable manufacturing via printing techniques. Moreover, due to their low dimensionality, CQDs exhibit quantum confinement and a high density of grain boundaries, which can be independently exploited to tune the Seebeck coefficient and thermal conductivity, respectively. This unique combination of attractive attributes makes CQDs very promising for application in emerging thermoelectric generator (TEG) technologies operating near room temperature. Herein, recent progress in CQDs for application in emerging thin‐film thermoelectrics is reviewed. First, the fundamental concepts of thermoelectricity in nanostructured materials are outlined, followed by an overview of the popular synthetic methods used to produce CQDs with controllable sizes and shapes. Recent strides in CQD‐based thermoelectrics are then discussed with emphasis on their application in thin‐film TEGs. Finally, the current challenges and future perspectives for further enhancing the performance of CQD‐based thermoelectric materials for future applications are discussed.
Mohamad Insan Nugraha, Ryanda Enggar Anugrah Ardhi, Dipti Naphade, Weimin Zhang, Youyou Yuan, Martin Heeney, and Thomas D. Anthopoulos
Royal Society of Chemistry (RSC)
Chlorinated solvents are commonly used to process organic semiconductor devices but have several negative environmental impacts.
Murali Gedda, Despoina Gkeka, Mohamad Insan Nugraha, Alberto D. Scaccabarozzi, Emre Yengel, Jafar I. Khan, Iain Hamilton, Yuanbao Lin, Marielle Deconinck, Yana Vaynzof,et al.
Wiley
AbstractThe high photoluminescence efficiency, color purity, extended gamut, and solution processability make low‐dimensional hybrid perovskites attractive for light‐emitting diode (PeLED) applications. However, controlling the microstructure of these materials to improve the device performance remains challenging. Here, the development of highly efficient green PeLEDs based on blends of the quasi‐2D (q2D) perovskite, PEA2Cs4Pb5Br16, and the wide bandgap organic semiconductor 2,7 dioctyl[1] benzothieno[3,2‐b]benzothiophene (C8‐BTBT) is reported. The presence of C8‐BTBT enables the formation of single‐crystal‐like q2D PEA2Cs4Pb5Br16 domains that are uniform and highly luminescent. Combining the PEA2Cs4Pb5Br16:C8‐BTBT with self‐assembled monolayers (SAMs) as hole‐injecting layers (HILs), yields green PeLEDs with greatly enhanced performance characteristics, including external quantum efficiency up to 18.6%, current efficiency up to 46.3 cd A−1, the luminance of 45 276 cd m−2, and improved operational stability compared to neat PeLEDs. The enhanced performance originates from multiple synergistic effects, including enhanced hole‐injection enabled by the SAM HILs, the single crystal‐like quality of the perovskite phase, and the reduced concentration of electronic defects. This work highlights perovskite:organic blends as promising systems for use in LEDs, while the use of SAM HILs creates new opportunities toward simpler and more stable PeLEDs.
Elisabeth A. Duijnstee, Benjamin M. Gallant, Philippe Holzhey, Dominik J. Kubicki, Silvia Collavini, Bernd K. Sturdza, Harry C. Sansom, Joel Smith, Matthias J. Gutmann, Santanu Saha,et al.
American Chemical Society (ACS)
Formamidinium lead triiodide (FAPbI3) is the leading candidate for single-junction metal–halide perovskite photovoltaics, despite the metastability of this phase. To enhance its ambient-phase stability and produce world-record photovoltaic efficiencies, methylenediammonium dichloride (MDACl2) has been used as an additive in FAPbI3. MDA2+ has been reported as incorporated into the perovskite lattice alongside Cl–. However, the precise function and role of MDA2+ remain uncertain. Here, we grow FAPbI3 single crystals from a solution containing MDACl2 (FAPbI3-M). We demonstrate that FAPbI3-M crystals are stable against transformation to the photoinactive δ-phase for more than one year under ambient conditions. Critically, we reveal that MDA2+ is not the direct cause of the enhanced material stability. Instead, MDA2+ degrades rapidly to produce ammonium and methaniminium, which subsequently oligomerizes to yield hexamethylenetetramine (HMTA). FAPbI3 crystals grown from a solution containing HMTA (FAPbI3-H) replicate the enhanced α-phase stability of FAPbI3-M. However, we further determine that HMTA is unstable in the perovskite precursor solution, where reaction with FA+ is possible, leading instead to the formation of tetrahydrotriazinium (THTZ-H+). By a combination of liquid- and solid-state NMR techniques, we show that THTZ-H+ is selectively incorporated into the bulk of both FAPbI3-M and FAPbI3-H at ∼0.5 mol % and infer that this addition is responsible for the improved α-phase stability.
Filip Aniés, Mohamad I. Nugraha, Arona Fall, Julianna Panidi, Yuxi Zhao, Patrice Vanelle, Leonidas Tsetseris, Julie Broggi, Thomas D. Anthopoulos, and Martin Heeney
Wiley
AbstractMolecular doping is a powerful and increasingly popular approach toward enhancing electronic properties of organic semiconductors (OSCs) past their intrinsic limits. The development of n‐type dopants has been hampered, however, by their poor stability and high air‐reactivity, a consequence of their generally electron rich nature. Here, the use of air‐stable carboxylated dopant precursors is reported to overcome this challenge. Active dopants are readily generated in solution by thermal decarboxylation and applied in n‐type organic field‐effect transistors (OFETs). Both 1,3‐dimethylimidazolium‐2‐carboxylate (CO2‐DMI) and novel dopant 1,3‐dimethylbenzimidazolium‐2‐carboxylate (CO2‐DMBI) are applied to n‐type OFETs employing well‐known organic semiconductors (OSCs) P(NDI2OD‐T2), PCBM, and O‐IDTBR. Successful improvement of performance in all devices demonstrates the versatility of the dopants across a variety of OSCs. Experimental and computational studies indicate that electron transfer from the dopant to the host OSC is preceded by decarboxylation of the precursor, followed by dimerization to form the active dopant species. Transistor studies highlight CO2‐DMBI as the most effective dopant, improving electron mobility by up to one order of magnitude, while CO2‐DMI holds the advantage of commercial availability.
Erdin Almuqoddas, Lia Yuliantini, Mohamad Insan Nugraha, Widhya Budiawan, Rimbi Rodiyana Sova, Brian Yuliarto, Shobih, Natalita Maulani Nursam, and Yuliar Firdaus
IEEE
Poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS) is widely used as a hole transport layer (HTL) in emerging solar cells. It is highly compatible with roll-to-roll deposition, paving the way for utilization in flexible solar cells. However, its mismatched energy levels and acidity limit its performance and stability. This study focuses on the modification of PEDOT:PSS HTL with vanadium oxide $\\left(V_{2} O_{5}\\right)$ additive to improve the performance of inverted $p-i-n$ perovskite solar cells (PSCs). The $V_{2} O_{5}$ was prepared from an aqueous ammonia solution and directly added to the PEDOT:PSS solution. Devices employing $V_{2} O_{5}$:PEDOT:PSS (VPP) HTL with a concentration of $8 mg/ml(w/v)$ exhibit remarkable performance improvement compared to devices using pristine PEDOT:PSS, with the power conversion efficiency (PCE) rising from 7.7 % to 9.0 %. Furthermore, key parameters, including open-circuit voltage ($V_{o c}$), short-circuit current ($J_{S C}$), and fill factor (FF), all showed improvements, recorded at 0.95 V, 16.0 $mAcm^{-2}$, and 58.6 %, respectively. Additionally, the responsiveness of light-to-current conversion exhibits a notable increase, highlighting the potential $V_{2}O_{5}$ additive, prepared using a simple method, to achieve superior performance in inverted p $i-n$ PSC. The finding also opens avenues for further exploration of other metal oxide additives, addressing specific challenges in HTL deposition.
Sophie Griggs, Adam Marks, Dilara Meli, Gonzague Rebetez, Olivier Bardagot, Bryan D. Paulsen, Hu Chen, Karrie Weaver, Mohamad I. Nugraha, Emily A. Schafer,et al.
Springer Science and Business Media LLC
AbstractOrganic electrochemical transistors are a promising technology for bioelectronic devices, with applications in neuromorphic computing and healthcare. The active component enabling an organic electrochemical transistor is the organic mixed ionic-electronic conductor whose optimization is critical for realizing high-performing devices. In this study, the influence of purity and molecular weight is examined for a p-type polythiophene and an n-type naphthalene diimide-based polymer in improving the performance and safety of organic electrochemical transistors. Our preparative GPC purification reduced the Pd content in the polymers and improved their organic electrochemical transistor mobility by ~60% and 80% for the p- and n-type materials, respectively. These findings demonstrate the paramount importance of removing residual Pd, which was concluded to be more critical than optimization of a polymer’s molecular weight, to improve organic electrochemical transistor performance and that there is readily available improvement in performance and stability of many of the reported organic mixed ionic-electronic conductors.
Yuanbao Lin, Yadong Zhang, Junxiang Zhang, Mantas Marcinskas, Tadas Malinauskas, Artiom Magomedov, Mohamad Insan Nugraha, Dimitris Kaltsas, Dipti R. Naphade, George T. Harrison,et al.
Wiley
AbstractThe influence of halogen substitutions (F, Cl, Br, and I) on the energy levels of the self‐assembled hole‐extracting molecule [2‐(9H‐Carbazol‐9‐yl)ethyl]phosphonic acid (2PACz), is investigated. It is found that the formation of self‐assembled monolayers (SAMs) of [2‐(3,6‐Difluoro‐9H‐carbazol‐9‐yl)ethyl]phosphonic acid (F‐2PACz), [2‐(3,6‐Dichloro‐9H‐carbazol‐9‐yl)ethyl]phosphonic acid (Cl‐2PACz), [2‐(3,6‐Dibromo‐9H‐carbazol‐9‐yl)ethyl]phosphonic acid (Br‐2PACz), and [2‐(3,6‐Diiodo‐9H‐carbazol‐9‐yl)ethyl]phosphonic acid (I‐2PACz) directly on indium tin oxide (ITO) increases its work function from 4.73 eV to 5.68, 5.77, 5.82, and 5.73 eV, respectively. Combining these ITO/SAM electrodes with the ternary bulk‐heterojunction (BHJ) system PM6:PM7‐Si:BTP‐eC9 yields organic photovoltaic (OPV) cells with power conversion efficiency (PCE) in the range of 17.7%–18.5%. OPVs featuring Cl‐2PACz SAMs yield the highest PCE of 18.5%, compared to cells with F‐2PACz (17.7%), Br‐2PACz (18.0%), or I‐2PACz (18.2%). Data analysis reveals that the enhanced performance of Cl‐2PACz‐based OPVs relates to the increased hole mobility, decreased interface resistance, reduced carrier recombination, and longer carrier lifetime. Furthermore, OPVs featuring Cl‐2PACz show enhanced stability under continuous illumination compared to ITO/PEDOT:PSS‐based cells. Remarkably, the introduction of the n‐dopant benzyl viologen into the BHJ further boosted the PCE of the ITO/Cl‐2PACz cells to a maximum value of 18.9%, a record‐breaking value for SAM‐based OPVs and on par with the best‐performing OPVs reported to date.
Wandi Wahyudi, Xianrong Guo, Viko Ladelta, Leonidas Tsetseris, Mohamad I. Nugraha, Yuanbao Lin, Vincent Tung, Nikos Hadjichristidis, Qian Li, Kang Xu,et al.
Wiley
AbstractSolvent‐solvent and solvent‐anion pairings in battery electrolytes have been identified for the first time by nuclear magnetic resonance spectroscopy. These hitherto unknown interactions are enabled by the hydrogen bonding induced by the strong Lewis acid Li+, and exist between the electron‐deficient hydrogen (δ+H) present in the solvent molecules and either other solvent molecules or negatively‐charged anions. Complementary with the well‐established strong but short‐ranged Coulombic interactions between cation and solvent molecules, such weaker but longer‐ranged hydrogen‐bonding casts the formation of an extended liquid structure in electrolytes that is influenced by their components (solvents, additives, salts, and concentration), which in turn dictates the ion transport within bulk electrolytes and across the electrolyte‐electrode interfaces. The discovery of this new inter‐component force completes the picture of how electrolyte components interact and arrange themselves, sets the foundation to design better electrolytes on the fundamental level, and probes battery performances.
Jian-Wei Liang, Yuliar Firdaus, Randi Azmi, Hendrik Faber, Dimitrios Kaltsas, Chun Hong Kang, Mohamad Insan Nugraha, Emre Yengel, Tien Khee Ng, Stefaan De Wolf,et al.
American Chemical Society (ACS)
Mohamad Insan Nugraha, Murali Gedda, Yuliar Firdaus, Alberto D. Scaccabarozzi, Weimin Zhang, Sanaa Alshammari, Filip Aniés, Begimai Adilbekova, Abdul‐Hamid Emwas, Iain McCulloch,et al.
Wiley
AbstractMolecular doping of organic semiconductors is often used to enhance their charge transport characteristics. Despite its success, however, most studies to date concern p‐doping with considerably fewer reports involving n‐dopants. Here, n‐doping of organic thin‐film transistors (OTFTs) based on several non‐fullerene acceptor (NFA) molecules using the recently developed diquat (DQ) as a soluble molecular dopant is reported. The low ionization potential of DQ facilitates efficient electron transfer and subsequent n‐doping of the NFAs, resulting in a consistent increase in the electron field‐effect mobility. Solution‐processed BTP‐eC9 and N3‐based OTFTs exhibit significant increase in the electron mobility upon DQ doping, with values increasing from 0.02 to 0.17 cm2 V–1 s–1 and from 0.2 to 0.57 cm2 V–1 s–1, respectively. A remarkable electron mobility of >1 cm2 V–1 s–1 is achieved for O‐IDTBR transistors upon optimal doping with DQ. The enhanced performance originates primarily from synergistic effects on electronic transport and changes in morphology, including: i) significant reduction of contact resistances, ii) formation of larger crystalline domains, iii) change of preferred crystal orientation, and iv) alteration in molecular packing motif. This work demonstrates the universality of DQ as an electronic additive for improving electron transport in OTFTs.
Safakath Karuthedath, Yuliar Firdaus, Alberto D. Scaccabarozzi, Mohamad Insan Nugraha, Shahidul Alam, Thomas D. Anthopoulos, and Frédéric Laquai
Wiley
In bulk heterojunction (BHJ) organic solar cells (OSC), the photoactive layer morphology controls charge carrier generation, transport, and extraction. Obtaining the “optimum” morphology is often achieved by empiric optimization of processing conditions and post‐processing treatment. Better control over the morphology can be achieved by sequential photoactive layer‐by‐layer (LbL) deposition techniques, creating a pseudo‐bilayer OSC. Solvent additives can be used to modify the vertical component distribution, thereby enhancing OSC efficiency. However, the impact of solvent additives on device photophysics is often unclear. Here, the photophysics of LbL‐coated PM6/Y6 organic solar cells are reported. Enhanced power conversion efficiencies (PCEs) are observed when using 1‐chloronaphthalene (CN) as a solvent additive. Transient absorption (TA) spectroscopy indicates that the addition of 0.5% CN facilitates both exciton dissociation and charge separation, while excessive (>1%) use of CN causes fast geminate and non‐geminate charge recombination and consequently deteriorates device performance. The results outline routes to fine‐tune the morphology of LbL‐coated photoactive layers of OSCs and provide insight into the reasons for increased PCEs.
Randi Azmi, Esma Ugur, Akmaral Seitkhan, Faisal Aljamaan, Anand S. Subbiah, Jiang Liu, George T. Harrison, Mohamad I. Nugraha, Mathan K. Eswaran, Maxime Babics,et al.
American Association for the Advancement of Science (AAAS)
If perovskite solar cells (PSCs) with high power conversion efficiencies (PCEs) are to be commercialized, they must achieve long-term stability, which is usually assessed with accelerated degradation tests. One of the persistent obstacles for PSCs has been successfully passing the damp-heat test (85°C and 85% relative humidity), which is the standard for verifying the stability of commercial photovoltaic (PV) modules. We fabricated damp heat–stable PSCs by tailoring the dimensional fragments of two-dimensional perovskite layers formed at room temperature with oleylammonium iodide molecules; these layers passivate the perovskite surface at the electron-selective contact. The resulting inverted PSCs deliver a 24.3% PCE and retain >95% of their initial value after >1000 hours at damp-heat test conditions, thereby meeting one of the critical industrial stability standards for PV modules.
Alberto D. Scaccabarozzi, Aniruddha Basu, Filip Aniés, Jian Liu, Osnat Zapata-Arteaga, Ross Warren, Yuliar Firdaus, Mohamad Insan Nugraha, Yuanbao Lin, Mariano Campoy-Quiles,et al.
American Chemical Society (ACS)
Electronic doping in organic materials has remained an elusive concept for several decades. It drew considerable attention in the early days in the quest for organic materials with high electrical conductivity, paving the way for the pioneering work on pristine organic semiconductors (OSCs) and their eventual use in a plethora of applications. Despite this early trend, however, recent strides in the field of organic electronics have been made hand in hand with the development and use of dopants to the point that are now ubiquitous. Here, we give an overview of all important advances in the area of doping of organic semiconductors and their applications. We first review the relevant literature with particular focus on the physical processes involved, discussing established mechanisms but also newly proposed theories. We then continue with a comprehensive summary of the most widely studied dopants to date, placing particular emphasis on the chemical strategies toward the synthesis of molecules with improved functionality. The processing routes toward doped organic films and the important doping-processing-nanostructure relationships, are also discussed. We conclude the review by highlighting how doping can enhance the operating characteristics of various organic devices.
Filip Aniés, Zhuoran Qiao, Mohamad Insan Nugraha, Aniruddha Basu, Thomas D. Anthopoulos, Nicola Gasparini, and Martin Heeney
Elsevier BV
Panagiota Kafourou, Mohamad Insan Nugraha, Aggelos Nikitaras, Luxi Tan, Yuliar Firdaus, Filip Aniés, Flurin Eisner, Bowen Ding, Jonas Wenzel, Martin Holicky,et al.
American Chemical Society (ACS)
Ita Rahmawati, Indriyati, Fitri A. Permatasari, Muhammad A. Irham, Mohamad I. Nugraha, Thomas D. Anthopoulos, and Ferry Iskandar
American Chemical Society (ACS)
Mohamad Insan Nugraha, Bin Sun, Hyunho Kim, Abdulrahman El-Labban, Saheena Desai, Neha Chaturvedi, Yi Hou, F. Pelayo Garcia de Arquer, Husam N. Alshareef, Edward H. Sargent,et al.
American Chemical Society (ACS)
Efficient thermoelectric generators require further progress in developing n-type semiconductors that combine low thermal conductivity with high electrical conductivity. By embedding colloidal quantum dots (CQDs) in a metal halide matrix (QDMH), the metal halide matrix can enhance phonon scattering, thus suppressing thermal transport; however, simultaneously achieving high electrical conductivity in such systems has previously been limited by the deleterious impact of a large density of interfaces on charge transport. Therefore, new strategies are needed to improve charge carrier transport without sacrificing matrix-enabled low thermal transport. Here, we report the use of chemical doping in the solution state to improve electron transport while maintaining low thermal transport in QDMH films. By incorporating cesium carbonate (Cs2CO3) salts as a dopant prior to matrix formation, we find that the dopant stabilizes the matrix in colloidal inks and enables efficient n-type doping in QDMH films. As a result, this strategy leads to an enhanced n-type thermoelectric behavior in solution-processed QDMH films near room temperature, with a thermal conductivity of 0.25 W m-1 K-1-significantly lower than in prior films based on organic-ligand-cross-linked CQD films (>0.6 W m-1 K-1) and spark-plasma-sintered CQD systems (>1 W m-1 K-1). This study provides a pathway to developing efficient n-type thermoelectric materials with low thermal conductivity using single-step deposition and low-temperature processing.
Hyunho Kim, Mohamad I. Nugraha, Xinwei Guan, Zhenwei Wang, Mrinal K. Hota, Xiangming Xu, Tom Wu, Derya Baran, Thomas D. Anthopoulos, and Husam N. Alshareef
American Chemical Society (ACS)
Fully solution-processed, large-area, electrical double-layer transistors (EDLTs) are presented by employing lead sulfide (PbS) colloidal quantum dots (CQDs) as active channels and Ti3C2Tx MXene as electrical contacts (including gate, source, and drain). The MXene contacts are successfully patterned by standard photolithography and plasma-etch techniques and integrated with CQD films. The large surface area of CQD film channels is effectively gated by ionic gel, resulting in high performance EDLT devices. A large electron saturation mobility of 3.32 cm2 V-1 s-1 and current modulation of 1.87 × 104 operating at low driving gate voltage range of 1.25 V with negligible hysteresis are achieved. The relatively low work function of Ti3C2Tx MXene (4.42 eV) compared to vacuum-evaporated noble metals such as Au and Pt makes them a suitable contact material for n-type transport in iodide-capped PbS CQD films with a LUMO level of ∼4.14 eV. Moreover, we demonstrate that the negative surface charges of MXene enhance the accumulation of cations at lower gate bias, achieving a threshold voltage as low as 0.36 V. The current results suggest a promising potential of MXene electrical contacts by exploiting their negative surface charges.
Binghao Wang, Alberto D. Scaccabarozzi, Haoyang Wang, Mari Koizumi, Mohamad Insan Nugraha, Yuanbao Lin, Yuliar Firdaus, Yan Wang, Sunghoon Lee, Tomoyuki Yokota,et al.
Royal Society of Chemistry (RSC)
This study introduces three different molecular dopants for near-infrared organic photodetectors. The doped organic photodetectors exhibit low dark current, high detectivity and good environmental stability, and can be used for pulse rate monitoring.
Jian Liu, Gang Ye, Hinderikus G. O. Potgieser, Marten Koopmans, Selim Sami, Mohamad Insan Nugraha, Diego Rosas Villalva, Hengda Sun, Jingjin Dong, Xuwen Yang,et al.
Wiley
AbstractThere is no molecular strategy for selectively increasing the Seebeck coefficient without reducing the electrical conductivity for organic thermoelectrics. Here, it is reported that the use of amphipathic side chains in an n‐type donor–acceptor copolymer can selectively increase the Seebeck coefficient and thus increase the power factor by a factor of ≈5. The amphipathic side chain contains an alkyl chain segment as a spacer between the polymer backbone and an ethylene glycol type chain segment. The use of this alkyl spacer does not only reduce the energetic disorder in the conjugated polymer film but can also properly control the dopant sites away from the backbone, which minimizes the adverse influence of counterions. As confirmed by kinetic Monte Carlo simulations with the host–dopant distance as the only variable, a reduced Coulombic interaction resulting from a larger host–dopant distance contributes to a higher Seebeck coefficient for a given electrical conductivity. Finally, an optimized power factor of 18 µW m–1 K–2 is achieved in the doped polymer film. This work provides a facile molecular strategy for selectively improving the Seebeck coefficient and opens up a new route for optimizing the dopant location toward realizing better n‐type polymeric thermoelectrics.
Yuliar Firdaus, Carr Hoi Yi Ho, Yuanbao Lin, Emre Yengel, Vincent M. Le Corre, Mohamad I. Nugraha, Emre Yarali, Franky So, and Thomas D. Anthopoulos
American Chemical Society (ACS)
Yuanbao Lin, Mohamad Insan Nugraha, Yuliar Firdaus, Alberto D. Scaccabarozzi, Filip Aniés, Abdul-Hamid Emwas, Emre Yengel, Xiaopeng Zheng, Jiakai Liu, Wandi Wahyudi,et al.
American Chemical Society (ACS)
Molecular doping has recently been shown to improve the operating characteristics of organic photovoltaics (OPVs). Here, we prepare neutral Diquat (DQ) and use it as n-dopant to improve the perform...
Jian Liu, Bas van der Zee, Riccardo Alessandri, Selim Sami, Jingjin Dong, Mohamad I. Nugraha, Alex J. Barker, Sylvia Rousseva, Li Qiu, Xinkai Qiu,et al.
Springer Science and Business Media LLC
AbstractThe ‘phonon-glass electron-crystal’ concept has triggered most of the progress that has been achieved in inorganic thermoelectrics in the past two decades. Organic thermoelectric materials, unlike their inorganic counterparts, exhibit molecular diversity, flexible mechanical properties and easy fabrication, and are mostly ‘phonon glasses’. However, the thermoelectric performances of these organic materials are largely limited by low molecular order and they are therefore far from being ‘electron crystals’. Here, we report a molecularly n-doped fullerene derivative with meticulous design of the side chain that approaches an organic ‘PGEC’ thermoelectric material. This thermoelectric material exhibits an excellent electrical conductivity of >10 S cm−1 and an ultralow thermal conductivity of <0.1 Wm−1K−1, leading to the best figure of merit ZT = 0.34 (at 120 °C) among all reported single-host n-type organic thermoelectric materials. The key factor to achieving the record performance is to use ‘arm-shaped’ double-triethylene-glycol-type side chains, which not only offer excellent doping efficiency (~60%) but also induce a disorder-to-order transition upon thermal annealing. This study illustrates the vast potential of organic semiconductors as thermoelectric materials.