Formerly the "Solar and Photovoltaic Engineering Research Center (SPERC)"

Recent Submissions

  • Metal Halide Perovskites for Solar-to-Chemical Fuel Conversion

    Chen, Jie; Dong, Chunwei; Idriss, Hicham; Mohammed, Omar F.; Bakr, Osman (Advanced Energy Materials, Wiley, 2019-10-16) [Article]
    This review article presents and discusses the recent progress made in the stabilization, protection, improvement, and design of halide perovskite-based photocatalysts, photoelectrodes, and devices for solar-to-chemical fuel conversion. With the target of water splitting, hydrogen iodide splitting, and CO2 reduction reactions, the strategies established for halide perovskites used in photocatalytic particle-suspension systems, photoelectrode thin-film systems, and photovoltaic-(photo)electrocatalysis tandem systems are organized and introduced. Moreover, recent achievements in discovering new and stable halide perovskite materials, developing protective and functional shells and layers, designing proper reaction solution systems, and tandem device configurations are emphasized and discussed. Perspectives on the future design of halide perovskite materials and devices for solar-to-chemical fuel conversion are provided. This review may serve as a guide for researchers interested in utilizing halide perovskite materials for solar-to-chemical fuel conversion.
  • High-speed colour-converting photodetector with all-inorganic CsPbBr3 perovskite nanocrystals for ultraviolet light communication

    Kang, Chun Hong; Dursun, Ibrahim; Liu, Guangyu; Sinatra, Lutfan; Sun, Xiaobin; Kong, Meiwei; Pan, Jun; Maity, Partha; Ooi, Ee-Ning; Ng, Tien Khee; Mohammed, Omar F.; Bakr, Osman; Ooi, Boon S. (Light: Science & Applications, Springer Science and Business Media LLC, 2019-10-16) [Article]
    Optical wireless communication (OWC) using the ultra-broad spectrum of the visible-to-ultraviolet (UV) wavelength region remains a vital field of research for mitigating the saturated bandwidth of radio-frequency (RF) communication. However, the lack of an efficient UV photodetection methodology hinders the development of UV-based communication. The key technological impediment is related to the low UV-photon absorption in existing silicon photodetectors, which offer low-cost and mature platforms. To address this technology gap, we report a hybrid Si-based photodetection scheme by incorporating CsPbBr3 perovskite nanocrystals (NCs) with a high photoluminescence quantum yield (PLQY) and a fast photoluminescence (PL) decay time as a UV-to-visible colour-converting layer for high-speed solar-blind UV communication. The facile formation of drop-cast CsPbBr3 perovskite NCs leads to a high PLQY of up to ~73% and strong absorption in the UV region. With the addition of the NC layer, a nearly threefold improvement in the responsivity and an increase of ~25% in the external quantum efficiency (EQE) of the solar-blind region compared to a commercial silicon-based photodetector were observed. Moreover, time-resolved photoluminescence measurements demonstrated a decay time of 4.5 ns under a 372-nm UV excitation source, thus elucidating the potential of this layer as a fast colour-converting layer. A high data rate of up to 34 Mbps in solar-blind communication was achieved using the hybrid CsPbBr3–silicon photodetection scheme in conjunction with a 278-nm UVC light-emitting diode (LED). These findings demonstrate the feasibility of an integrated high-speed photoreceiver design of a composition-tuneable perovskite-based phosphor and a low-cost silicon-based photodetector for UV communication.
  • Deciphering photocarrier dynamics for tuneable high-performance perovskite-organic semiconductor heterojunction phototransistors

    Lin, Yen-Hung; Huang, Wentao; Pattanasattayavong, Pichaya; Lim, Jongchul; Li, Ruipeng; Sakai, Nobuya; Panidi, Julianna; Hong, Min Ji; Ma, Chun; Wei, Nini; Wehbe, Nimer; Fei, Zhuping; Heeney, Martin; Labram, John G.; Anthopoulos, Thomas D.; Snaith, Henry J. (Nature Communications, Springer Science and Business Media LLC, 2019-10-02) [Article]
    Looking beyond energy harvesting, metal-halide perovskites offer great opportunities to revolutionise large-area photodetection technologies due to their high absorption coefficients, long diffusion lengths, low trap densities and simple processability. However, successful extraction of photocarriers from perovskites and their conversion to electrical signals remain challenging due to the interdependency of photogain and dark current density. Here we report hybrid hetero-phototransistors by integrating perovskites with organic semiconductor transistor channels to form either “straddling-gap” type-I or “staggered-gap” type-II heterojunctions. Our results show that gradual transforming from type-II to type-I heterojunctions leads to increasing and tuneable photoresponsivity with high photogain. Importantly, with a preferential edge-on molecular orientation, the type-I heterostructure results in efficient photocarrier cycling through the channel. Additionally, we propose the use of a photo-inverter circuitry to assess the phototransistors’ functionality and amplification. Our study provides important insights into photocarrier dynamics and can help realise advanced device designs with “on-demand” optoelectronic properties.
  • MAPbI3 Single Crystals Free from Hole-Trapping Centers for Enhanced Photodetectivity

    Yang, Chen; El Demellawi, Jehad K.; Yin, Jun; Velusamy, Dhinesh; Emwas, Abdul-Hamid M.; El-Zohry, Ahmed M.; Gereige, Issam; AlSaggaf, Ahmed; Bakr, Osman; Alshareef, Husam N.; Mohammed, Omar F. (ACS Energy Letters, American Chemical Society (ACS), 2019-10-01) [Article]
    Perovskite single crystals (PSCs) are considered the next breakthrough in optoelectronics research due to their free-grain boundary and much lower density of trap states compared to those of their polycrystalline counterparts. However, the inevitable formation of triiodide-based intrinsic defects during high-temperature crystal growth is one of the major challenges impeding the further development of optoelectronic devices based on PSCs. Here, we not only identified the existence of these triiodide ions as hole-trapping centers and their tremendous negative impact on the performance of PSCs, but more importantly, we used a reduction treatment to prevent their formation during crystal growth. The removal of such defect centers resulted in much higher charge carrier mobility and longer carrier lifetime than the untreated counterparts, leading to enhanced photodetection properties. The I3–-free MAPbI3 single crystal (MSC) devices consistently generated a more than 100 times higher photocurrent than that generated by I3–-rich devices under the same light intensity.
  • 17% Efficient Organic Solar Cells Based on Liquid Exfoliated WS2 as a Replacement for PEDOT:PSS

    Lin, Yuanbao; Adilbekova, Begimai; Firdaus, Yuliar; Yengel, Emre; Faber, Hendrik; Sajjad, Muhammad; Zheng, Xiaopeng; Yarali, Emre; Seitkhan, Akmaral; Bakr, Osman; El Labban, Abdulrahman; Schwingenschlögl, Udo; Tung, Vincent; McCulloch, Iain; Laquai, Frédéric; Anthopoulos, Thomas D. (Advanced Materials, Wiley, 2019-10-01) [Article]
    The application of liquid-exfoliated 2D transition metal disulfides (TMDs) as the hole transport layers (HTLs) in nonfullerene-based organic solar cells is reported. It is shown that solution processing of few-layer WS2 or MoS2 suspensions directly onto transparent indium tin oxide (ITO) electrodes changes their work function without the need for any further treatment. HTLs comprising WS2 are found to exhibit higher uniformity on ITO than those of MoS2 and consistently yield solar cells with superior power conversion efficiency (PCE), improved fill factor (FF), enhanced short-circuit current (JSC), and lower series resistance than devices based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and MoS2. Cells based on the ternary bulk-heterojunction PBDB-T-2F:Y6:PC71BM with WS2 as the HTL exhibit the highest PCE of 17%, with an FF of 78%, open-circuit voltage of 0.84 V, and a JSC of 26 mA cm−2. Analysis of the cells' optical and carrier recombination characteristics indicates that the enhanced performance is most likely attributed to a combination of favorable photonic structure and reduced bimolecular recombination losses in WS2-based cells. The achieved PCE is the highest reported to date for organic solar cells comprised of 2D charge transport interlayers and highlights the potential of TMDs as inexpensive HTLs for high-efficiency organic photovoltaics.
  • Use of the Phen-NaDPO:Sn(SCN) 2 Blend as Electron Transport Layer Results to Consistent Efficiency Improvements in Organic and Hybrid Perovskite Solar Cells

    Seitkhan, Akmaral; Neophytou, Marios; Kirkus, Mindaugas; Abou-Hamad, Edy; Hedhili, Mohamed N.; Yengel, Emre; Firdaus, Yuliar; Faber, Hendrik; Lin, Yuanbao; Tsetseris, Leonidas; McCulloch, Iain; Anthopoulos, Thomas D. (Advanced Functional Materials, Wiley, 2019-09-27) [Article]
    A simple approach that enables a consistent enhancement of the electron extracting properties of the widely used small-molecule Phen-NaDPO and its application in organic solar cells (OSCs) is reported. It is shown that addition of minute amounts of the inorganic molecule Sn(SCN)2 into Phen-NaDPO improves both the electron transport and its film-forming properties. Use of Phen-NaDPO:Sn(SCN)2 blend as the electron transport layer (ETL) in binary PM6:IT-4F OSCs leads to a remarkable increase in the cells' power conversion efficiency (PCE) from 12.6% (Phen-NaDPO) to 13.5% (Phen-NaDPO:Sn(SCN)2). Combining the hybrid ETL with the best-in-class organic ternary PM6:Y6:PC70BM systems results to a similarly remarkable PCE increase from 14.2% (Phen-NaDPO) to 15.6% (Phen-NaDPO:Sn(SCN)2). The consistent PCE enhancement is attributed to reduced trap-assisted carrier recombination at the bulk-heterojunction/ETL interface due to the presence of new energy states formed upon chemical interaction of Phen-NaDPO with Sn(SCN)2. The versatility of this hybrid ETL is further demonstrated with its application in perovskite solar cells for which an increase in the PCE from 16.6% to 18.2% is also demonstrated.
  • Direct Patterning of Highly Conductive PEDOT:PSS/Ionic Liquid Hydrogel via Microreactive Inkjet Printing.

    Teo, Mei Ying; RaviChandran, Narrendar; Kim, Nara; Kee, Seyoung; Stuart, Logan; Aw, Kean C; Stringer, Jonathan (ACS applied materials & interfaces, American Chemical Society (ACS), 2019-09-20) [Article]
    The gelation of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has gained popularity for its potential applications in three dimensions, while possessing tissue-like mechanical properties, high conductivity, and biocompatibility. However, the fabrication of arbitrary structures, especially via inkjet printing, is challenging because of the inherent gel formation. Here, microreactive inkjet printing (MRIJP) is utilized to pattern various 2D and 3D structures of PEDOT:PSS/IL hydrogel by in-air coalescence of PEDOT:PSS and ionic liquid (IL). By controlling the in-air position and Marangoni-driven encapsulation, single droplets of the PEDOT:PSS/IL hydrogel as small as a diameter of ≈260 μm are fabricated within ≈600 μs. Notably, this MRIJP-based PEDOT:PSS/IL has potential for freeform patterning while maintaining identical performance to those fabricated by the conventional spin-coating method. Through controlled deposition achieved via MRIJP, PEDOT:PSS/IL can be transformed into different 3D structures without the need for molding, potentially leading to substantial progress in next-generation bioelectronics devices.
  • Outstanding Challenges of Zero-Dimensional Perovskite Materials

    Mohammed, Omar F. (The Journal of Physical Chemistry Letters, American Chemical Society (ACS), 2019-09-19) [Article]
  • Ultrathin channels make transistors go faster

    Anthopoulos, Thomas D. (Nature Materials, Springer Science and Business Media LLC, 2019-09-19) [Article]
    Reducing the thickness of an amorphous conductive indium tin oxide layer down to a few nanometres has enabled the realization of 40-nm-long channel transistors with remarkable operating characteristics.
  • Halogen Vacancies Enable Ligand-Assisted Self-Assembly of Perovskite Quantum Dots into Nanowires.

    Pan, Jun; Li, Xiyan; Gong, Xiwen; Yin, Jun; Zhou, Dianli; Sinatra, Lutfan; Huang, Renwu; Liu, Jiakai; Chen, Jie; Dursun, Ibrahim; El-Zohry, Ahmed M.; Saidaminov, Makhsud I.; Sun, Hong-Tao; Mohammed, Omar F.; Ye, Changhui; Sargent, E.; Bakr, Osman (Angewandte Chemie (International ed. in English), Wiley, 2019-09-19) [Article]
    Interest has been growing in defects of halide perovskites in view of their intimate connection with key material optoelectronic properties. In perovskite quantum dots (PQDs), the influence of defects is even more apparent than in their bulk counterparts. By combining experiment and theory, we report herein a halide-vacancy-driven, ligand-directed self-assembly process of CsPbBr3 PQDs. With the assistance of oleic acid and didodecyldimethylammonium sulfide, surface-Br-vacancy-rich CsPbBr3 PQDs self-assemble into nanowires (NWs) that are 20-60 nm in width and several millimeters in length. The NWs exhibit a sharp photoluminescence profile (≈18 nm full-width at-half-maximum) that peaks at 525 nm. Our findings provide insight into the defect-correlated dynamics of PQDs and defect-assisted fabrication of perovskite materials and devices.
  • Passivating contacts for crystalline silicon solar cells

    Allen, Thomas; Bullock, James; Yang, Xinbo; Javey, Ali; De Wolf, Stefaan (Nature Energy, Springer Science and Business Media LLC, 2019-09-16) [Article]
    The global photovoltaic (PV) market is dominated by crystalline silicon (c-Si) based technologies with heavily doped, directly metallized contacts. Recombination of photo-generated electrons and holes at the contact regions is increasingly constraining the power conversion efficiencies of these devices as other performance-limiting energy losses are overcome. To move forward, c-Si PV technologies must implement alternative contacting approaches. Passivating contacts, which incorporate thin films within the contact structure that simultaneously supress recombination and promote charge-carrier selectivity, are a promising next step for the mainstream c-Si PV industry. In this work, we review the fundamental physical processes governing contact formation in c-Si. In doing so we identify the role passivating contacts play in increasing c-Si solar cell efficiencies beyond the limitations imposed by heavy doping and direct metallization. Strategies towards the implementation of passivating contacts in industrial environments are discussed.
  • Interfacial Engineering at the 2D/3D Heterojunction for High-Performance Perovskite Solar Cells.

    Niu, Tianqi; Lu, Jing; Jia, Xuguang; Xu, Zhuo; Tang, Ming-Chun; Barrit, Dounya; Yuan, Ningyi; Ding, Jianning; Zhang, Xu; Fan, Yuanyuan; Luo, Tao; Zhang, Yalan; Smilgies, Detlef-M.; Liu, Zhike; Amassian, Aram; Jin, Shengye; Zhao, Kui; Liu, Shengzhong (Frank) (Nano letters, American Chemical Society (ACS), 2019-09-04) [Article]
    Perovskite solar cells based on two-dimensional/three-dimensional (2D/3D) hierarchical structure have attracted significant attention in recent years due to their promising photovoltaic performance and stability. However, obtaining a detailed understanding of interfacial mechanism at the 2D/3D heterojunction, for example, the ligand-chemistry-dependent nature of the 2D/3D heterojunction and its influence on charge collection and the final photovoltaic outcome, is not yet fully developed. Here we demonstrate the underlying 3D phase templates growth of quantum wells (QWs) within a 2D capping layer, which is further influenced by the fluorination of spacers and compositional engineering in terms of thickness distribution and orientation. Better QW alignment and faster dynamics of charge transfer at the 2D/3D heterojunction result in higher charge mobility and lower charge recombination loss, largely explaining the significant improvements in charge collection and open-circuit voltage (VOC) in complete solar cells. As a result, 2D/3D solar cells with a power-conversion efficiency of 21.15% were achieved, significantly higher than the 3D counterpart (19.02%). This work provides key missing information on how interfacial engineering influences the desirable electronic properties of the 2D/3D hierarchical films and device performance via ligand chemistry and compositional engineering in the QW layer.
  • Pillar[5]arene Stabilized Silver Nanoclusters: Immense Stability and Luminescence Enhancement Induced by Host-Guest Interactions.

    Muhammed, Madathumpady; Cruz, Laila; Emwas, Abdul-Hamid M.; El-Zohry, Ahmed; Moosa, Basem; Mohammed, Omar F.; Khashab, Niveen M. (Angewandte Chemie (International ed. in English), Wiley, 2019-08-29) [Article]
    Herein, we report the synthesis of a new class of functional silver nanoclusters (AgNCs) capped with pillar[5]arene (P5) based host ligands. These NCs are readily prepared via direct synthesis or ligand exchange synthesis and are stable at room temperature for over 4 months. The pillar[5]arene stabilized NCs (Ag29(LA-P5)12(TPP)2) endorse reversible host-guest interactions with neutral alkylamines and cationic quaternary ammonium guests. This results into the formation of spherical assemblies with unparalleled changes in their optical properties including an astonishing ≈2000-fold luminescence enhancement. This is the highest luminescence enhancement ratio reported so far for such atomically precise NCs. Our synthetic protocol paves the way for the preparation of a new generation of metal nanoclusters protected by macrocyclic ligands with molecular recognition and selectivity toward specific guests.
  • Membrane-Free Detection of Metal Cations with an Organic Electrochemical Transistor

    Wustoni, Shofarul; Combe, Craig; ohayon, David; Akhtar, Mahmood Hassan; McCulloch, Iain; Inal, Sahika (Advanced Functional Materials, Wiley, 2019-08-26) [Article]
    Alkali-metal ions, particularly sodium (Na+) and potassium (K+), are the messengers of living cells, governing a cascade of physiological processes through the action of ion channels. Devices that can monitor, in real time, the concentrations of these cations in aqueous media are in demand not only for the study of cellular machinery, but also to detect conditions in the human body that lead to electrolyte imbalance. In this work, conducting polymers are developed that respond rapidly and selectively to varying concentrations of Na+ and K+ in aqueous media. These polymer films, bearing crown-ether-functionalized thiophene units specific to either Na+ or K+, generate an electrical output proportional to the cation type and concentration. Using electropolymerization, the ion-selective polymers are integrated as the gate electrode of an organic electrochemical transistor (OECT). The OECT current changes with respect to the concentration of the ion to which the polymer electrode is selective. Designed as a single, miniaturized chip, the OECT enables the selective detection of the cations within a physiologically relevant range. These electrochemical ion sensors require neither ion-selective membranes nor a reference electrode to operate and have the potential to surpass existing technologies for the detection of alkali-metal ions in aqueous media.
  • Short Excited-State Lifetimes Enable Photo-Oxidatively Stable Rubrene Derivatives

    Ly, Jack; Martin, Kara; Thomas, Simil; Yamashita, Masataka; Yu, Beihang; Pointer, Craig A.; Yamada, Hiroko; Carter, Kenneth R.; Parkin, Sean; Zhang, Lei; Bredas, Jean-Luc; Young, Elizabeth R.; Briseno, Alejandro L. (Journal of Physical Chemistry A, American Chemical Society (ACS), 2019-08-26) [Article]
    A series of rubrene derivatives were synthesized and the influence of the side group in enhancing photo-oxidative stability was evaluated. Photo-oxidation half-lives were determined via UV-vis absorption spectroscopy, which revealed thiophene containing derivatives to be the most stable species. The electron affinity of the compounds did not correlate with stability as previously reported in literature. Our work shows that shorter excited-state lifetimes result in increased photo-oxidative stability in these rubrene derivatives. These results confirm that faster relaxation kinetics out-compete the formation of reactive oxygen species that ultimately degrade linear oligoacenes. This report highlights the importance of using molecular design to tune excited-state lifetimes in order to generate more stable oligoacenes.
  • Layer-Dependent Coherent Acoustic Phonons in Two-Dimensional Ruddlesden–Popper Perovskite Crystals

    Maity, Partha; Yin, Jun; Cheng, Bin; He, Jr-Hau; Bakr, Osman; Mohammed, Omar F. (The Journal of Physical Chemistry Letters, American Chemical Society (ACS), 2019-08-22) [Article]
    By combining femtosecond transient reflectance (TR) spectroscopy and density functional theory (DFT) calculations, we reveal the impact of the length of the organic linkers (HOC2H4NH3+ and C6H5C2H4NH3+) and the number of inorganic layers (n = 1–3) on the hot carrier relaxation dynamics and coherent acoustic phonons in 2D Ruddlesden–Popper (RP) perovskites. We find that the interplay between the hot carriers and the coherent longitudinal acoustic phonons (CLAPs) can extend the oscillation of the TR kinetics to nanoseconds, which could lead to the higher thermal conductivities of 2D RP perovskites. Moreover, we find that the frequency of the acoustic phonon oscillation and phonon velocity decreases with the increasing number of layers due to the increased mass of the inorganic layers and reduced electron–phonon coupling. This finding provides new physical insights into how the organic spacers and number of inorganic layers control the overall carrier dynamics of 2D perovskite materials.
  • Quantum Dots Supply Bulk- and Surface-Passivation Agents for Efficient and Stable Perovskite Solar Cells

    Zheng, Xiaopeng; Troughton, Joel; Gasparini, Nicola; Lin, Yuanbao; Wei, Mingyang; Hou, Yi; Liu, Jiakai; Song, Kepeng; Chen, Zhaolai; Yang, Chen; Turedi, Bekir; Alsalloum, Abdullah; Pan, Jun; Chen, Jie; Zhumekenov, Ayan A.; Anthopoulos, Thomas D.; Han, Yu; Baran, Derya; Mohammed, Omar F.; Sargent, Edward H.; Bakr, Osman (Joule, Cell, 2019-08-21) [Article]
    We report a facile processing strategy that utilizes perovskite quantum dots (QDs) to distribute elemental dopants uniformly across a MAPbI3 film and anchor ligands to the film's surface—reducing the film's trap-state density and rendering its surface hydrophobic. QD-treated MAPbI3 films yield solar cells with 21.5% power conversion efficiency (PCE) (versus 18.3% for non-QD-treated) and maintain 80% of their initial PCE under 1-sun continuous illumination for 500 h with improved thermal stability.
  • Performance and Stability Improvement of Layered NCM Lithium-Ion Batteries at High Voltage by a Microporous Al2O3 Sol–Gel Coating

    Wu, Yingqiang; Li, Mengliu; Wahyudi, Wandi; Sheng, Guan; Miao, Xiaohe; Anthopoulos, Thomas D.; Huang, Kuo-Wei; Li, Yangxing; Lai, Zhiping (ACS Omega, American Chemical Society (ACS), 2019-08-19) [Article]
    A simple and low-cost polymer-aided sol–gel method was developed to prepare γ-Al2O3 protective layers for LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode materials. The selected polyvinyl alcohol polymer additive not only facilitates the formation of a uniform and thin γ-Al2O3 layer on the irregular and rough cathode particle surface to protect it from corrosion but also serves as a pore-forming agent to generate micropores in the film after sintering to allow fast transport of lithium ions, which guaranteed the excellent and stable battery performance at high working voltage. Detailed studies in the full battery mode showed that the leached corrosion species from the cathode had a more profound harmful effect to the graphite anode, which seemed to be the dominating factor that caused the battery performance decay.
  • Metal Halide Perovskite and Phosphorus Doped g-C3N4 Bulk Heterojunctions for Air-Stable Photodetectors

    Liu, Zhixiong; Zhu, Yunpei; El Demellawi, Jehad K.; Velusamy, Dhinesh; El-Zohry, Ahmed M.; Bakr, Osman; Mohammed, Omar F.; Alshareef, Husam N. (ACS Energy Letters, American Chemical Society (ACS), 2019-08-19) [Article]
    In this work, we fabricate photodetectors made of methylammonium lead trihalide perovskite (MLHP) and phosphorus-doped graphitic carbon nitride nanosheets (PCN-S). Using thermal polymerization, PCN-S with a reduced band gap, are synthesized from low-cost precursors, making it feasible to form type-II bulk heterojunctions with perovskites. Owing to the bulk heterojunctions between PCN-S and MLHP, the dark current of the photodetectors significantly decreases from ∼10-9 A for perovskite-only devices to ∼10-11 A for heterojunction devices. As a result, not only does the on/off ratio of the hybrid devices increase from 103 to 105 but also the photodetectivity is enhanced by more than 1 order of magnitude (up to 1013 Jones) and the responsivity reaches a value of 14 A W-1. Moreover, the hybridization of MLHP with PCN-S significantly modifies the hydrophilicity and morphology of the perovskite films, which dramatically increases their stability under ambient conditions. The hybrid photodetectors, described here, present a promising new direction toward stable and efficient optoelectronic applications.
  • Fused Cyclopentadithienothiophene Acceptor Enables Ultrahigh Short-Circuit Current and High Efficiency >11% in As-Cast Organic Solar Cells

    He, Qiao; Shahid, Munazza; Wu, Jiaying; Jiao, Xuechen; Eisner, Flurin D.; Hodsden, Thomas; Fei, Zhuping; Anthopoulos, Thomas D.; McNeill, Christopher R.; Durrant, James R.; Heeney, Martin (Advanced Functional Materials, Wiley, 2019-08-08) [Article]
    A new method to synthesize an electron-rich building block cyclopentadithienothiophene (9H-thieno-[3,2-b]thieno[2″,3″:4′,5′]thieno[2′,3′:3,4]cyclopenta[1,2-d]thiophene, CDTT) via a facile aromatic extension strategy is reported. By combining CDTT with 1,1-dicyanomethylene-3-indanone endgroups, a promising nonfullerene small molecule acceptor (CDTTIC) is prepared. As-cast, single-junction nonfullerene organic solar cells based on PFBDB-T: CDTTIC blends exhibit very high short-circuit currents up to 26.2 mA cm−2 in combination with power conversion efficiencies over 11% without any additional processing treatments. The high photocurrent results from the near-infrared absorption of the CDTTIC acceptor and the well-intermixed blend morphology of polymer donor PFBDB-T and CDTTIC. This work demonstrates a useful fused ring extension strategy and promising solar cell results, indicating the great potential of the CDTT derivatives as electron-rich building blocks for constructing high-performance small molecule acceptors in organic solar cells.

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