Now showing items 1-20 of 1757

    • Engineering kesterite based photocathode for photoelectrochemical ammonia synthesis from NOx reduction

      Zhou, Shujie; Sun, Kaiwen; Toe, Cui Ying; Yin, Jun; Huang, Jialiang; Zeng, Yiyu; Zhang, Doudou; Chen, Weijian; Mohammed, Omar F.; Hao, Xiaojing; Amal, Rose (Advanced Materials, Wiley, 2022-05-23) [Article]
      Ammonia is a key chemical feedstock for industry as well as future carbon-free fuel and transportable vector for renewable energy. Photoelectrochemical (PEC) ammonia synthesis from NOx reduction reaction (NOx RR) provides not only a promising alternative to the energy-intensive Haber-Bosch process through direct solar-to-ammonia conversion, but a sustainable solution for balancing the global nitrogen cycle by restoring ammonia from wastewater. In this work, we, for the first time, demonstrated selective ammonia synthesis from PEC NOx RR by kesterite (Cu2 ZnSnS4 (CZTS)) photocathode through loading defect-engineered TiOx cocatalyst on CdS/CZTS photocathode (TiOx /CdS/CZTS). The uniquely designed photocathode enables selective ammonia production from NOx RR, yielding up to 89.1% faradaic efficiency (0.1 V versus reversible hydrogen electrode (RHE)) with a remarkable positive onset potential (0.38 V versus RHE). By tailoring the amount of surface defective Ti3+ species, the adsorption of reactant NO3- and * NO2 intermediate is significantly promoted while the full coverage of TiOx also suppresses NO2- liberation as a by-product, contributing to high ammonia selectivity. Our further attempted PEC ammonia synthesis from simulated wastewater shows good faradaic efficiency of 64.9%, unveiling the potential of using kesterite based photocathode for sustainably restoring ammonia from nitrate-rich wastewater.
    • Mechanistic insights into photochemical nickel-catalyzed cross-couplings enabled by energy transfer

      Kancherla, Rajesh; Muralirajan, Krishnamoorthy; Maity, Bholanath; Karuthedath, Safakath; Kumar, Gadde Sathish; Laquai, Frédéric; Cavallo, Luigi; Rueping, Magnus (Nature Communications, Springer Science and Business Media LLC, 2022-05-18) [Article]
      Various methods that use a photocatalyst for electron transfer between an organic substrate and a transition metal catalyst have been established. While triplet sensitization of organic substrates via energy transfer from photocatalysts has been demonstrated, the sensitization of transition metal catalysts is still in its infancy. Here, we describe the selective alkylation of C(sp3)–H bonds via triplet sensitization of nickel catalytic intermediates with a thorough elucidation of its reaction mechanism. Exergonic Dexter energy transfer from an iridium photosensitizer promotes the nickel catalyst to the triplet state, thus enabling C–H functionalization via the release of bromine radical. Computational studies and transient absorption experiments support that the reaction proceeds via the formation of triplet states of the organometallic nickel catalyst by energy transfer.
    • Soft perovskites stabilized by robust heterojunctions

      Wu, Zhifang; Alsalloum, Abdullah; Mohammed, Omar F.; Bakr, Osman (Joule, Elsevier BV, 2022-05-18) [Article]
      Rapid progress has recently been made in the development of perovskite solar cells (PSCs) with power conversion efficiencies (PCEs) that are now comparable with those of crystalline Si, the traditional and well-established solar cell technology. Recently in Science, Fang and co-workers reported a PSC in an inverted configuration with a high efficiency of >24% (23.5% certified) and remarkable operational stability. In this work, robust heterojunctions were constructed at the interface to suppress ion migration and favorably adjust the interfacial energy band alignment, addressing two major issues associated with the poor PCEs and stability of inverted PSCs.
    • Photoactivated p-Doping of Organic Interlayer Enables Efficient Perovskite/Silicon Tandem Solar Cells

      Zheng, Xiaopeng; Liu, Jiang; Liu, Tuo; Aydin, Erkan; Chen, Min; Yan, Wenbo; de Bastiani, Michele; Allen, Thomas; Yuan, Shuai; Kirmani, Ahmad R.; Baustert, Kyle N.; Salvador, Michael; Turedi, Bekir; Alsalloum, Abdullah Yousef; Almasabi, Khulud M.; Kotsovos, Konstantinos; Gereige, Issam; Liao, Liang-Sheng; Luther, Joseph; Graham, Kenneth R.; Mohammed, Omar F.; De Wolf, Stefaan; Bakr, Osman (ACS Energy Letters, American Chemical Society (ACS), 2022-05-17) [Article]
      Solution-processed organic semiconductor layers on rough surfaces tend to vary widely in thickness, significantly hindering charge extraction in relevant optoelectronic devices. Herein, we report the photoactivated p-doping of hole-transporting material (HTM) to enhance hole extraction for (textured) perovskite/silicon tandem solar cells, making the device performance less sensitive to the variation of hole transport layer thickness. We used the ionic compound 4-isopropyl-4′-methyldiphenyliodonium tetrakis(penta-fluorophenyl-borate) (DPI-TPFB) as a p-type dopant in poly(triaryl amine) (PTAA), which we used as the HTM. We observed that light soaking DPI-TPFB-doped PTAA shows approximately 22 times higher conductivity compared with an undoped PTAA film, which translated into an improved fill factor (FF) for tandem solar cells. Our tandem solar cells achieved an ∼80% FF and 27.8% efficiency and operated at their maximum power point for 200 h without loss of performance, in addition to retaining ∼83% of initial performance over a month of operation in an outdoor environment.
    • Probing Ultrafast Interfacial Carrier Dynamics in Metal Halide Perovskite Films and Devices by Transient Reflection Spectroscopy

      Gao, Yajun; Liu, Jiang; Isikgor, Furkan Halis; Wang, Mingcong; Khan, Jafar Iqbal; De Wolf, Stefaan; Laquai, Frédéric (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2022-05-13) [Article]
      Interfaces in metal halide perovskite (MHP) solar cells cause carrier recombination and thereby reduce their power conversion efficiency. Here, ultrafast (picosecond to nanosecond) transient reflection (TR) spectroscopy has been used to probe interfacial carrier dynamics in thin films of the reference MHP MAPbI3 and state-of-the-art (Cs0.15MA0.15FA0.70)Pb(Br0.20I0.80)3 (CsFAMA). First, MAPbI3 films in contact with fullerene-based charge extraction layers (CTLs) in the presence and absence of LiF used as an interlayer (ITL) were studied. To quantify and discriminate between interface-induced and bulk carrier recombination, we employed a one-dimensional diffusion and recombination model. The interface-induced carrier recombination velocity was found to be 1229 ± 78 cm s–1 in nonpassivated MAPbI3 films, which was increased to 2248 ± 75 cm s–1 when MAPbI3 interfaced directly with C60, whereas it was reduced to 145 ± 63 cm s–1 when inserting a 1 nm thin LiF interlayer between MAPbI3 and C60, in turn improving the open-circuit voltage of devices by 33 mV. Second, the effect of surface and grain boundary passivation by PhenHCl in CsFAMA was revealed. Here, the recombination velocity decreased from 605 ± 52 to 0.16 ± 5.28 and 7.294 ± 34.5 cm s–1, respectively. The approach and data analysis presented here are immediately applicable to other perovskite/interlayer/CTL interfaces and passivation protocols, and they add to our understanding of the impact of surfaces and interfaces in MHP-based thin films on carrier recombination and device efficiency.
    • Light-induced activation of boron doping in hydrogenated amorphous silicon for over 25% efficiency silicon solar cells

      Liu, Wenzhu; Shi, Jianhua; Zhang, Liping; Han, Anjun; Huang, Shenglei; Li, Xiaodong; Peng, Jun; Yang, Yuhao; Gao, Yajun; Yu, Jian; Jiang, Kai; Yang, Xinbo; Li, Zhenfei; Zhao, Wenjie; Du, Junlin; Song, Xin; Yin, Jun; Wang, Jie; Yu, Youlin; Shi, Qiang; Ma, Zhixin; Zhang, Haichuan; Ling, Jiajia; Xu, Lujia; Kang, Jingxuan; Xu, Fuzong; Liu, Jiang; Liu, Hanyuan; Xie, Yi; Meng, Fanying; De Wolf, Stefaan; Laquai, Frédéric; Di, Zengfeng; Liu, Zhengxin (Nature Energy, Springer Science and Business Media LLC, 2022-05-12) [Article]
      Recent achievements in amorphous/crystalline silicon heterojunction (SHJ) solar cells and perovskite/SHJ tandem solar cells place hydrogenated amorphous silicon (a-Si:H) at the forefront of photovoltaics. Due to the extremely low effective doping efficiency of trivalent boron in amorphous tetravalent silicon, light harvesting of aforementioned devices is limited by their fill factors (FFs), a direct metric of the charge carrier transport. It is challenging but crucial to develop highly conductive doped a-Si:H with minimal FF losses. Here we report that light soaking can efficiently boost the dark conductance of boron-doped a-Si:H thin films. Light induces diffusion and hopping of weakly bound hydrogen atoms, which activates boron doping. The effect is reversible and the dark conductivity decreases over time when the solar cell is no longer illuminated. By implementing this effect to SHJ solar cells, we achieved a certified total-area power conversion efficiency of 25.18% with a FF of 85.42% on a 244.63 cm2 wafer.
    • Quantitative Analysis of Nanorough Hydrogenated Si(111) Surfaces through Vibrational Spectral Assignment by Periodic DFT Calculations

      Holovský, Jakub; Šebera, Jakub; Sychrovský, Vladimír; Zemen, Jan; De Wolf, Stefaan; Ballif, Christophe (The Journal of Physical Chemistry C, American Chemical Society (ACS), 2022-05-09) [Article]
      In this work, we use periodic density functional theory (periodic DFT) to rigorously assign vibrational spectra measured on nanorough wet-processed hydrogenated Si(111) surfaces. We compare Si(111)-(1 × 1) surfaces etched by dilute HF and NH4F, featuring two vibrational patterns that systematically appear together. They are attributed to vibrations observed on vicinal surfaces featuring 112̅ and 1̅1̅2 steps terminated with monohydrides and dihydrides, respectively. For the first time, we fully assign vibration patterns of realistic silicon surfaces with variable nanoroughness directly by periodic DFT simulations involving contributions from isolated species but also contributions from highly coupled species forming standing waves. This work opens the path to a better quantitative characterization of imperfect and nanorough Si(111) surfaces from vibrational spectra.
    • Room-temperature ferromagnetism in two-dimensional transition metal chalcogenides: Strategies and origin

      Cai, Liang; Tung, Vincent; Wee, Andrew (Journal of Alloys and Compounds, Elsevier BV, 2022-05-07) [Article]
      Room-temperature (RT) ferromagnetic atomically thin transition metal chalcogenides (TMCs) provide a novel platform for discovering new physical phenomena in the two-dimensional (2D) limit and developing the next-generation spintronic applications. Recent progress in exploring the RT ferromagnetism in 2D TMCs have attracted significant interest from experimental and theoretical scientists; However, the semiconducting TMCs are non-magnetic. In parallel, the inconsistency of magnetism between density functional theory (DFT) calculations and experimental results persist in both TMC semiconductors and metals. We review the strategies for RT ferromagnetism in 2D TMC semiconductors and the origin of RT ferromagnetism in 2D TMC metals, followed by the discussion of promising future directions in the area of RT ferromagnetic 2D TMC materials.
    • Self-assembly enables simple structure organic photovoltaics via green-solvent and open-air-printing: Closing the lab-to-fab gap

      Tang, Hua; Lv, Jie; Liu, Kuan; Ren, Zhiwei; Chandran, Hrisheekesh Thachoth; Huang, Jiaming; Zhang, Ying; Xia, Hao; Khan, Jafar Iqbal; Hu, Dingqin; Yan, Cenqi; Oh, Jiyeon; Chen, Shanshan; Chu, Shenglong; Fong, Patrick W.K.; Chen, Haiyan; Xiao, Zhengguo; Yang, Changduk; Kan, Zhipeng; Laquai, Frédéric; Lu, Shirong; Li, Gang (Materials Today, Elsevier BV, 2022-04-29) [Article]
      The ultimate goal of organic solar cells (OSCs) is to deliver cheap, stable, efficient, scalable, and eco-friendly solar-to-power products contributing to the global carbon neutral. However, simultaneously balancing these five critical factors of OSCs toward commercialization is extremely challenging. Herein, a green-solvent-processable and open-air-printable self-assembly strategy is demonstrated to synchronously simplify the device architecture, improve the power conversion efficiency (PCE) and enhance the shelf, thermal as well as light illumination stability of OSCs. The cathode interlayer (CIL)-free self-assembled OSCs exhibit the PCE of 15.5%, higher than that of traditional inverted OSCs of 13.0%, which is among the top values for both CIL-free self-assembled OSCs and open-air blade-coated bulk-heterojunction OSCs. The remarkable enhancements are mainly ascribed to the finely self-assembly, subtly controlled donor/acceptor aggregation rate, and delicately manipulated vertical morphology. Besides, this strategy enables 13.2% efficiency on device area of 0.98 cm2, implying its potential for scalability. These findings demonstrate that this strategy can close the lab-to-fab gap of OSCs toward commercialized cheap, stable, efficient, scalable, and eco-friendly OSCs.
    • Stretchable Redox-active Semiconducting Polymers for High-performance Organic Electrochemical Transistors

      Dai, Yahao; Dai, Shilei; Li, Nan; Li, Yang; Moser, Maximilian; Strzalka, Joseph; Prominski, Aleksander; Liu, Youdi; Zhang, Qingteng; Li, Songsong; Hu, Huawei; Liu, Wei; Chatterji, Shivani; Cheng, Ping; Tian, Bozhi; McCulloch, Iain; Xu, Jie; Wang, Sihong (Advanced Materials, Wiley, 2022-04-21) [Article]
      Organic electrochemical transistor (OECT) is an emerging device platform for next-generation bioelectronics owing to its uniquely high amplification and sensitivity to biological signals. For achieving seamless tissue-electronics interfaces for accurate signal acquisition, skin-like softness and stretchability are essential requirements, which have not yet been imparted onto high-performance OECTs, largely due to the lack of stretchable redox-active semiconducting polymers. Here, we report a stretchable semiconductor for OECT devices, namely poly(2-(3,3'-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-[2,2'-bithiophen]-5)yl thiophene) (p(g2T-T)), which gives exceptional stretchability over 200% strain and 5000 repeated stretching cycles, together with the OECT performance on par with the state of the art. Validated by the systematic characterizations and the comparisons of different polymers, the key design features of this polymer that enable the combination of high stretchability and high OECT performance are non-linear backbone architecture, moderate side-chain density, and sufficiently high molecular weight. Using this highly stretchable polymer semiconductor, we fabricated an intrinsically stretchable OECT with the high normalized transconductance (∼223 S cm-1 ) and biaxial stretchability up to 100% strain. Furthermore, we demonstrate on-skin electrocardiogram (ECG) recording that combines built-in amplification and unprecedented skin conformability.
    • Interface Engineering of Bi-Fluorescence Molecules for High-Performance Data Encryption and Ultralow UV-Light Detection

      Wang, Jian-Xin; Gutiérrez-Arzaluz, Luis; Yin, Jun; Maity, Partha; Zhou, Yang; Chen, Cailing; Han, Yu; Bakr, Osman; Eddaoudi, Mohamed; Mohammed, Omar F. (Advanced Optical Materials, Wiley, 2022-04-14) [Article]
      It is extremely difficult if not impossible to effectively and precisely regulate the luminescence of organic chromophores from different electronic excited states through external stimuli for use in light-conversion devices. This is mainly due to the difficulty in breaking Kasha's rule by large energy separation and stabilization of different emissive electronic excited states. Here, the authors address this great challenge in a single experiment by expanding the utility of a monounsaturated omega-9 fatty acid (oleic acid) capped with organic chromophores as a new and efficient luminescent regulator. More specifically, the authors have successfully promoted the use of oleic acid as an efficient and reversible switch that can precisely regulate chromophore luminescence. These time-resolved absorption and luminescence experiments, along with density functional theory calculations have clearly demonstrated that ultrafast electron transfer from oleic acid to the difluoroboron β-diketonate (DFBK) chromophores efficiently blocks the intramolecular charge transfer process of DFBK chromophores, and activates the locally excited state luminescence, leading to different emission colors from different electronic excited states for ultralow UV-light detection and high-performance data encryption.
    • Efficient bandgap widening in co-evaporated MAPbI(3) perovskite

      Dewi, Herlina Arianita; Li, Jia; Erdenebileg, Enkhtur; Wang, Hao; de Bastiani, Michele; De Wolf, Stefaan; Mathews, Nripan; Mhaisalkar, Subodh; Bruno, Annalisa (SUSTAINABLE ENERGY & FUELS, Royal Society of Chemistry (RSC), 2022-04-13) [Article]
      Co-evaporated perovskite solar cells (PSCs) have demonstrated outstanding properties, such as great scalability, intrinsic stability, high-power conversion efficiency (PCE), and fabrication adaptability even on rough surfaces. At present, MAPbI3 is the most used co-evaporated perovskite due to the complexity of forming multi-component compositions by thermal evaporation. Even though PSCs with high PCEs have been obtained, the MAPbI3 bandgap (∼1.60 eV) is not ideal for multijunction devices. In this work, we propose a facile method to increase the bandgap of co-evaporated MAPbI3 (∼1.60 eV) through a MABr-based treatment. The best MABr-treated perovskite composition films show a bandgap of 1.66 eV (MAPb(Br0.18I0.82)3) and exhibit good spectral stability under continuous 1-sun illumination at the ambient conditions of 28 °C and 70% relative humidity. This hybrid method works efficiently for thick co-evaporated MAPbI3 films (∼750 nm), which is unusual for hybrid processes. The n-i-p PSCs built from the MAPb(Br0.18I0.82)3 films exhibit a blue-shifted external quantum efficiency and a Voc increase of ∼30 mV as compared to the pure MAPbI3 PSCs, in agreement with the bandgap widening observed in the films. This hybrid method to crete wide bandgap perovskites can be universally applied to MAPbI3 deposited on both flat and textured surfaces and shows great promise for its integration in monolithic tandems.
    • Sources and Mechanism of Degradation in p-Type Thiophene-Based Organic Electrochemical Transistors

      Schafer, Emily A.; Wu, Ruiheng; Meli, Dilara; Tropp, Joshua; Moser, Maximilian; McCulloch, Iain; Paulsen, Bryan D.; Rivnay, Jonathan (ACS Applied Electronic Materials, American Chemical Society (ACS), 2022-04-12) [Article]
      Achieving high stability is critical for the implementation of organic electrochemical transistors (OECTs) in more diverse and demanding applications. However, the sources and mechanisms of OECT degradation have not been rigorously explored. Here, we employ a variety of biasing schemes to separate the relative effects of oxidative bias stress, reductive bias stress, and current stress on degradation of thiophene-based, p-type OECTs. We find that accelerated degradation arises from the compounding effects of simultaneous oxidative and reductive bias stress and is common across several thiophene-based channel materials. To understand the underlying mechanism of OECT channel degradation, we explore the individual contributions of dissolved oxygen and source-drain electrode materials. We determine that the reaction of dissolved oxygen at the buried Au/OMIEC interface of the drain electrode experiencing reductive potentials produces a mobile reactive species that aggressively degrades the oxidized OMIEC throughout the device, destroying its conjugation and disrupting electronic charge transport. Importantly, we find that this mechanism can be disrupted by alternatively removing oxygen, avoiding reductive potentials in the device biasing scheme, replacing Au electrodes with a noncatalytic alternative, or passivating Au electrodes with self-assembled monolayers. These conclusions can inform both future standards of stability testing in the field as well as design considerations of OECT implementation in long-term applications.
    • Illumination-dependent temperature coefficients of the electrical parameters of modern silicon solar cell architectures

      Zhang, Simon M.F.; Seif, Johannes P.; Abbott, Malcolm D.; Le, Anh Huy Tuan; Allen, Thomas; Perez-Wurfl, Ivan; Hameiri, Ziv (Nano Energy, Elsevier BV, 2022-04-12) [Article]
      Photovoltaic devices operate under a wide range of temperature and illumination conditions. While the temperature coefficients (TC) of crystalline silicon solar cells have been well-studied, there have been only a few investigations regarding the effect of illumination on TCs. In this study, the TCs of the main electrical parameters of various silicon solar cell technologies are first determined. The illumination spectrum dependence of the TC of the short-circuit current and the illumination intensity dependence of the TC of the open-circuit voltage are then investigated. For the latter investigation, a custom-designed temperature-dependent Suns-VOC system is used. It is found that: (1) the TC of the short-circuit current measured using an A-rated spectrum may differ from the TC measured using the AM1.5G spectrum by up to 30%, (2) the TC of the open-circuit voltage of all technologies at 0.001 suns approximately doubles compared to at one-sun, and (3) silicon heterojunction cells seem to have the overall best TC performance at medium to high intensities
    • Metal–Organic Frameworks in Mixed-Matrix Membranes for High-Speed Visible-Light Communication

      Wang, Jian-Xin; Wang, Yue; Nadinov, Issatay; Yin, Jun; Gutierrez Arzaluz, Luis; Healing, George; Alkhazragi, Omar; Cheng, Youdong; Jia, Jiangtao; Alsadun, Norah Sadun; Kale, Vinayak Swamirao; Kang, Chun Hong; Ng, Tien Khee; Shekhah, Osama; Alshareef, Husam N.; Bakr, Osman; Eddaoudi, Mohamed; Ooi, Boon S.; Mohammed, Omar F. (Journal of the American Chemical Society, American Chemical Society (ACS), 2022-04-12) [Article]
      Mixed-matrix membranes (MMMs) based on luminescent metal-organic frameworks (MOFs) and emissive polymers with the combination of their unique advantages have great potential in separation science, sensing, and light-harvesting applications. Here, we demonstrate MMMs for the field of high-speed visible-light communication (VLC) using a very efficient energy transfer strategy at the interface between a MOF and an emissive polymer. Our steady-state and ultrafast time-resolved experiments, supported by high-level density functional theory calculations, revealed that efficient and ultrafast energy transfer from the luminescent MOF to the luminescent polymer can be achieved. The resultant MMMs exhibited an excellent modulation bandwidth of around 80 MHz, which is higher than those of most well-established color-converting phosphors commonly used for optical wireless communication. Interestingly, we found that the efficient energy transfer further improved the light communication data rate from 132 Mb/s of the pure polymer to 215 Mb/s of MMMs. This finding not only showcases the promise of the MMMs for high-speed VLC but also highlights the importance of an efficient and ultrafast energy transfer strategy for the advancement of data rates of optical wireless communication.
    • Insight into the role of reduced graphene oxide in enhancing photocatalytic hydrogen evolution in disordered carbon nitride.

      Rahman, Mohammad Ziaur; Maity, Partha; Mohammed, Omar F.; Gascon, Jorge (Royal Society of Chemistry (RSC), 2022-04-12) [Article]
      Compared to crystalline carbon nitride, the performance of disordered carbon nitride (d-CN) as a hydrogen production photocatalyst is extremely poor. Owing to its disordered atomic orientation, it is prone to numerous defect states. These energy states are potential sites for trapping and recombination of photogenerated charge carriers. As a result, rapid recombination of photogenerated charge carriers places a fundamental photophysical challenge in charge separation and transport, which inhibits its photocatalytic activity. In the presence of reduced graphene oxide (rGO), d-CN shows enhanced photocatalytic production of hydrogen. However, photophysical insight into the tacit role of rGO is not well understood which limits the rational design of d-CN as a photocatalyst. Particularly, understanding of the early time-scale (in fs to ps) recombination mechanism and the charge transport kinetics has not yet been achieved. With the help of ultrafast transient absorption spectroscopy, femtosecond time-resolved photoluminescence spectroscopy and transient photocurrent measurements, this article deciphers the ultrafast dynamics of the separation and transport of photogenerated charge carriers in d-CN facilitated by rGO. It is found that rGO substantially suppresses the bimolecular and trap-assisted recombination and enables a faster separation of charge carriers. As a result, it increases the lifetime of the charge carriers to be transported to the surface catalytic sites, and therefore, augments the rate of hydrogen production almost by an order of magnitude. Our findings therefore offer a proof-of-concept for overcoming the trap-mediated recombination problems in disordered carbon nitride.
    • Chlorine-Infused Wide-Band Gap p-CuSCN/n-GaN Heterojunction Ultraviolet-Light Photodetectors

      Liang, Jian Wei; Firdaus, Yuliar; Kang, Chun Hong; Min, Jungwook; Min, Jung-Hong; Al Ibrahim, Redha H.; Wehbe, Nimer; Hedhili, Mohamed N.; Kaltsas, Dimitrios; Tsetseris, Leonidas; Lopatin, Sergei; Zheng, Shuiqin; Ng, Tien Khee; Anthopoulos, Thomas D.; Ooi, Boon S. (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2022-04-11) [Article]
      Copper thiocyanate (CuSCN) is a p-type semiconductor that exhibits hole-transport and wide-band gap (∼3.9 eV) characteristics. However, the conductivity of CuSCN is not sufficiently high, which limits its potential application in optoelectronic devices. Herein, CuSCN thin films were exposed to chlorine using a dry etching system to enhance their electrical properties, yielding a maximum hole concentration of 3 × 1018 cm–3. The p-type CuSCN layer was then deposited onto an n-type gallium nitride (GaN) layer to form a prototypical ultraviolet-based photodetector. X-ray photoelectron spectroscopy further demonstrated the interface electronic structures of the heterojunction, confirming a favorable alignment for holes and electrons transport. The ensuing p-CuSCN/n-GaN heterojunction photodetector exhibited a turn-on voltage of 2.3 V, a responsivity of 1.35 A/W at −1 V, and an external quantum efficiency of 5.14 × 102% under illumination with ultraviolet light (peak wavelength of 330 nm). The work opens a new pathway for making a plethora of hybrid optoelectronic devices of inorganic and organic nature by using p-type CuSCN as the hole injection layer.
    • Quantum-size-tuned heterostructures enable efficient and stable inverted perovskite solar cells

      Chen, Hao; Teale, Sam; Chen, Bin; Hou, Yi; Grater, Luke; Zhu, Tong; Bertens, Koen; Park, So Min; Atapattu, Harindi R.; Gao, Yajun; Wei, Mingyang; Johnston, Andrew K.; Zhou, Qilin; Xu, Kaimin; Yu, Danni; Han, Congcong; Cui, Teng; Jung, Eui Hyuk; Zhou, Chun; Zhou, Wenjia; Proppe, Andrew H.; Hoogland, Sjoerd; Laquai, Frédéric; Filleter, Tobin; Graham, Kenneth R.; Ning, Zhijun; Sargent, E. (Nature Photonics, Springer Science and Business Media LLC, 2022-04-07) [Article]
      The energy landscape of reduced-dimensional perovskites (RDPs) can be tailored by adjusting their layer width (n). Recently, two/three-dimensional (2D/3D) heterostructures containing n = 1 and 2 RDPs have produced perovskite solar cells (PSCs) with >25% power conversion efficiency (PCE). Unfortunately, this method does not translate to inverted PSCs due to electron blocking at the 2D/3D interface. Here we report a method to increase the layer width of RDPs in 2D/3D heterostructures to address this problem. We discover that bulkier organics form 2D heterostructures more slowly, resulting in wider RDPs; and that small modifications to ligand design induce preferential growth of n ≥ 3 RDPs. Leveraging these insights, we developed efficient inverted PSCs (with a certified quasi-steady-state PCE of 23.91%). Unencapsulated devices operate at room temperature and around 50% relative humidity for over 1,000 h without loss of PCE; and, when subjected to ISOS-L3 accelerated ageing, encapsulated devices retain 92% of initial PCE after 500 h.
    • Unleashing the Full Power of Perovskite/Silicon Tandem Modules with Solar Trackers

      Babics, Maxime; de Bastiani, Michele; Balawi, Ahmed Hesham; Ugur, Esma; Aydin, Erkan; Subbiah, Anand Selvin; Liu, Jiang; Xu, Lujia; Azmi, Randi; Allen, Thomas; Rehman, Atteq Ur; Altmann, Thomas; Salvador, Michael; De Wolf, Stefaan (ACS Energy Letters, American Chemical Society (ACS), 2022-04-06) [Article]
      Perovskite/silicon tandem photovoltaics is a promising technology to exceed the performance limit of single-junction solar cells. For utility-scale photovoltaic plants, trends and forecasts indicate that bifacial modules mounted on solar trackers will increasingly dominate the market in the next 20 years. In line with this roadmap, we investigate the outdoor performance of perovskite/silicon tandem solar cells mounted on a horizontal single-axis solar tracker in an environment with elevated solar insolation and albedo. We experimentally demonstrate in such conditions that a bifacial monolithic tandem solar cell installed on a tracker can generate 55% more power than an equivalent tandem mounted on a fixed rack. On the basis of our results, we anticipate a significant economic advantage by coupling bifacial monolithic perovskite/silicon tandem technology with solar trackers.
    • Efficient Piezoelectric Energy Harvesting from a Discrete Hybrid Bismuth Bromide Ferroelectric Templated by Phosphonium Cation

      Deswal, Swati; Panday, Rishukumar; Naphade, Dipti R.; Dixit, Prashant; Praveenkumar, Balu; Zaręba, Jan K.; Anthopoulos, Thomas D.; Ogale, Satishchandra; Boomishankar, Ramamoorthy (Chemistry – A European Journal, Wiley, 2022-03-31) [Article]
      Bismuth containing hybrid molecular ferroelectrics are receiving tremendous attention in recent years owing to their stable and non-toxic composition. However, these perovskite-like structures are primarily limited to ammonium cations. Herein, we report a new phosphonium based discrete perovskite-like hybrid ferroelectric with a formula [Me(Ph) 3 P] 3 [Bi 2 Br 9 ] ( MTPBB ) and its mechanical energy harvesting capability. The Polarization-Electric field ( P-E ) measurements resulted in a well-defined ferroelectric hysteresis loop with a remnant polarization value of 2.1 µ C cm -2 . Piezoresponse force microscopy experiments enabled visualization of the ferroelectric domain structure and evaluation of the piezoelectric strain coefficient ( d 33 ) for an  MTPBB single crystal and thin film sample. Furthermore, flexible devices incorporating MTPBB in polydimethylsiloxane (PDMS) matrix at various concentrations were fabricated and explored for their mechanical energy harvesting properties. The champion device with 20 wt. % of MTPBB in PDMS rendered a maximum peak-to-peak open-circuit voltage of 22.9 V and a maximum power density of 7 µ W cm -2 at an optimal load of 4 MΩ. Moreover, the potential of MTPBB -based devices in low power electronics was demonstrated by storing the harvested energy in various electrolytic capacitors.