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The significant contact resistance at the metal-semiconductor interface is a well-documented issue for organic thin-film transistors (OTFTs) that hinders device and circuit performance. Here, this issue is tackled by developing three new thiol carbazole-based self-assembled monolayer (SAM) molecules, namely tBu-2SCz, 2SCz, and Br-2SCz, and utilizing them as carrier-selective injection interlayers. The SAMs alter the work function of gold electrodes by more than 1 eV, making them suitable for use in hole and electron-transporting OTFTs. Scanning tunneling microscopy analysis indicates that 2SCz and Br-2SCz form highly ordered molecular rows, resulting in work function values of 4.86 and 5.48 eV, respectively. The latter value is higher than gold electrodes modified by the commonly used pentafluorobenzenethiol (≈5.33 eV), making Br-2SCz promising for hole injection. Conversely, tBu-2SCz appears disordered with a lower work function of 4.52 eV, making it more suitable for electron injection. These intriguing properties are leveraged to demonstrate hole- and electron-transporting OTFTs with improved operating characteristics. All-organic complementary inverters are finally demonstrated by integrating p- and n-channel OTFTs, showcasing the potential of this simple yet powerful contact work function engineering approach. The present study highlights the versatility of thiol carbazole SAMs as carrier injecting interlayers for OTFTs and integrated circuits., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

Ultrathin SiO x layers and c-Si/SiO x interfaces find application in tunnel-oxide passivated contacts (TOPcon) for high-efficiency silicon solar cells. Here, we investigate their detailed microscopic properties, with specific attention for the case of c-Si(100) substrates, capped either by p-type or n-type poly-silicon layers [c-Si/SiO x /poly-Si (p + ) or c-Si/SiO x /poly-Si (n + )]. Our focus is on the effects of the substrate preparation conditions (either by a dry-plasma or wet SiO x process) and the high-temperature annealing step (as required for the poly-Si crystallization) on the SiO x stoichiometry and its microscopic structure. Through advanced photoemission techniques, we find a clearly decreased valence band offset between the c-Si and SiO x (from 4.5 eV to 4.15 eV) when comparing the dry SiO x with the wet SiO x process, independent of the SiO x film thickness, but correlating with the relative fraction of sub-stochiometric Si states. We lastly examine the magnitude of band-bending of the contact structure through controlled in-situ exposure to light of the surfaces and subsequent tracking of core and valence band levels via a surface photovoltage and a junction photo-voltage (JPV) effect. By analyzing this JPV effect qualitatively, we find it to be proportional to the expected quasi fermi level splitting within the c-Si wafer., (© 2024 Wiley-VCH GmbH.)

Single crystal perovskites have garnered significant attention as potential replacements for existing absorber layer materials. Despite the extensive investigations on their photoinduced charge-carriers dynamics, most of the time-resolved techniques focus on bulk properties, neglecting surface characteristic which plays a crucial role for their optoelectronic performance. Herein, 4D ultrafast scanning electron microscopy (4D-USEM) is utilized to probing the photogenerated carrier transport at the first few nanometers, alongside density functional theory (DFT) to track both defect centers and ions migration. Two compositions of mixed cation are investigated: FA 0.6 MA 0.4 PbI 3 and FA 0.4 MA 0.6 PbI 3 , interestingly, the former displays a longer lifetime compared to the latter due the presence of a higher surface-defect centers. DFT calculations fully support that revealing samples with higher FA content have a lower energy barrier for iodide ions to migrate from the bulk to top layer, assisting in passivating surface vacancies, and a higher energy diffusion barrier to escape from surface to vacuum, resulting in fewer vacancies and longer-lived hole-electron pairs. These findings manifest the influence of cation selection on charge carrier transport and formation of defects, and emphasize the importance of understanding ion migrations role in controlling surface vacancies to assist engineering high-performance optoelectronic devices based on single crystal perovskites., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Solution-processed high-performing ambipolar organic phototransistors (OPTs) can enable low-cost integrated circuits. Here, a heteroatom engineering approach to modify the electron affinity of a low band gap diketopyrrolopyrole (DPP) co-polymer, resulting in well-balanced charge transport, a more preferential edge-on orientation and higher crystallinity, is demonstrated. Changing the comonomer heteroatom from sulfur (benzothiadiazole (BT)) to oxygen (benzooxadiazole (BO)) leads to an increased electron affinity and introduces higher ambipolarity. Organic thin film transistors fabricated from the novel PDPP-BO exhibit charge carrier mobility of 0.6 and 0.3 cm 2  Vs⁻ 1 for electrons and holes, respectively. Due to the high sensitivity of the PDPP-based material and the balanced transport in PDPP-BO, its application as an NIR detector in an OPT architecture is presented. By maintaining a high on/off ratio (9 × 10 4 ), ambipolar OPTs are shown with photoresponsivity of 69 and 99 A W⁻ 1 and specific detectivity of 8 × 10 7 for the p-type operation and 4 × 10 9 Jones for the n-type regime. The high symmetric NIR-ambipolar OPTs are also evaluated as ambipolar photo-inverters, and show a 46% gain enhancement under illumination., (© 2024 The Authors. Advanced Materials published by Wiley‐VCH GmbH.)

Electron-transporting (n-type) conjugated polymers have recently been applied in numerous electrochemical applications, where both ion and electron transport are required. Despite continuous efforts to improve their performance and stability, n-type conjugated polymers with mixed conduction still lag behind their hole-transporting (p-type) counterparts, limiting the functions of electrochemical devices. In this work, we investigate the effect of enhanced backbone coplanarity on the electrochemical activity and mixed ionic-electronic conduction properties of n-type polymers during operation in aqueous media. Through substitution of the widely employed electron-deficient naphthalene diimide (NDI) unit for the core-extended naphthodithiophene diimide (NDTI) units, the resulting polymer shows a more planar backbone with closer packing, leading to an increase in the electron mobility in organic electrochemical transistors (OECTs) by more than two orders of magnitude. The NDTI-based polymer shows a deep-lying lowest unoccupied molecular orbital level, enabling operation of the OECT closer to 0 V vs Ag/AgCl, where fewer parasitic reactions with molecular oxygen occur. Enhancing the backbone coplanarity also leads to a lower affinity toward water uptake during cycling, resulting in improved stability during continuous electrochemical charging and ON-OFF switching relative to the NDI derivative. Furthermore, the NDTI-based polymer also demonstrates near-perfect shelf-life stability over a month-long test, exhibiting a negligible decrease in both the maximum on-current and transconductance. Our results highlight the importance of polymer backbone design for developing stable, high-performing n-type materials with mixed ionic-electronic conduction in aqueous media., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The performance of perovskite solar cells with inverted polarity (p-i-n) is still limited by recombination at their electron extraction interface, which also lowers the power conversion efficiency (PCE) of p-i-n perovskite-silicon tandem solar cells. A MgF x interlayer with thickness of ~1 nanometer at the perovskite/C 60 interface favorably adjusts the surface energy of the perovskite layer through thermal evaporation, which facilitates efficient electron extraction and displaces C 60 from the perovskite surface to mitigate nonradiative recombination. These effects enable a champion open-circuit voltage of 1.92 volts, an improved fill factor of 80.7%, and an independently certified stabilized PCE of 29.3% for a monolithic perovskite-silicon tandem solar cell ~1 square centimeter in area. The tandem retained ~95% of its initial performance after damp-heat testing (85°C at 85% relative humidity) for >1000 hours.

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.

A facile solvothermal synthesis approach for chemical composition control in ternary Bi-S-I systems is reported by simply controlling the sulfide concentration. We demonstrate the application of these bismuth-based ternary mixed-anion compounds as high capacity anode materials in rechargeable batteries. Cells utilising Bi 13 S 18 I 2 achieved an initial capacity value of 807 mA h g -1 , while those with BiSI/Bi 13 S 18 I 2 a value of 1087 mA h g -1 in lithium-ion battery systems.

Understanding the adsorption and photoactivity of acetic acid and trimethyl acetic acid on TiO 2 surfaces is important for improving the performance of photocatalysts and dye-sensitized solar cells. Here we present a structural study of adsorption on rutile TiO 2 (100)-1 × 1 and -1 × 3 using Scanning Tunnelling Microscopy and Density Functional Theory calculations. Exposure of both terminations to acetic acid gives rise to a ×2 periodicity in the [001] direction (i.e., along Ti rows), with a majority ordered c(2 × 2) phase in the case of the 1 × 1 termination. The DFT calculations suggest that the preference of c(2 × 2) over the 2 × 1 periodicity found for TiO 2 (110)-1 × 1 can be attributed to an increase in interadsorbate Coulomb repulsion. Exposure of TiO 2 (100)-1 × 1 and -1 × 3 to trimethyl acetic acid gives rise to largely disordered structures due to steric effects, with quasi-order occurring in small areas and near step edges where these effects are reduced., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

In bulk heterojunction (BHJ) organic solar cells (OSCs) both the electron affinity (EA) and ionization energy (IE) offsets at the donor-acceptor interface should equally control exciton dissociation. Here, we demonstrate that in low-bandgap non-fullerene acceptor (NFA) BHJs ultrafast donor-to-acceptor energy transfer precedes hole transfer from the acceptor to the donor and thus renders the EA offset virtually unimportant. Moreover, sizeable bulk IE offsets of about 0.5 eV are needed for efficient charge transfer and high internal quantum efficiencies, since energy level bending at the donor-NFA interface caused by the acceptors' quadrupole moments prevents efficient exciton-to-charge-transfer state conversion at low IE offsets. The same bending, however, is the origin of the barrier-less charge transfer state to free charge conversion. Our results provide a comprehensive picture of the photophysics of NFA-based blends, and show that sizeable bulk IE offsets are essential to design efficient BHJ OSCs based on low-bandgap NFAs.

Three n-type fused lactam semiconducting polymers were synthesized for thermoelectric and transistor applications via a cheap, highly atom-efficient, and nontoxic transition-metal free aldol polycondensation. Energy level analysis of the three polymers demonstrated that reducing the central acene core size from two anthracenes ( A-A ), to mixed naphthalene-anthracene ( A-N ), and two naphthalene cores ( N-N ) resulted in progressively larger electron affinities, thereby suggesting an increasingly more favorable and efficient solution doping process when employing 4-(2,3-dihydro-1,3-dimethyl-1 H -benzimidazol-2-yl)- N , N -dimethylbenzenamine (N-DMBI) as the dopant. Meanwhile, organic field effect transistor (OFET) mobility data showed the N-N and A-N polymers to feature the highest charge carrier mobilities, further highlighting the benefits of aryl core contraction to the electronic performance of the materials. Ultimately, the combination of these two factors resulted in N-N , A-N , and A-A to display power factors (PFs) of 3.2 μW m -1 K -2 , 1.6 μW m -1 K -2 , and 0.3 μW m -1 K -2 , respectively, when doped with N-DMBI, whereby the PFs recorded for N-N and A-N are among the highest reported in the literature for n-type polymers. Importantly, the results reported in this study highlight that modulating the size of the central acene ring is a highly effective molecular design strategy to optimize the thermoelectric performance of conjugated polymers, thus also providing new insights into the molecular design guidelines for the next generation of high-performance n-type materials for thermoelectric applications.

Highly efficient perovskite solar cells (PSCs) fabricated in the classic n-i-p configuration generally employ triphenylamine-based hole-transport layers (HTLs) such as spiro-OMeTAD, PTAA, and poly-TPD. Controllable doping of such layers has been critical to achieve increased conductivity and high device performance. To this end, LiTFSI/tBP doping and subsequent air exposure is widely utilized. However, this approach often leads to low device stability and reproducibility. Departing from this point, we introduce the Lewis acid tris(pentafluorophenyl)borane (TPFB) as an effective dopant, resulting in a significantly improved conductivity and lowered surface potential for triphenylamine-based HTLs. Here, we specifically investigated spiro-OMeTAD, which is the most widely used HTL for n-i-p devices, and revealed improved power conversion efficiency (PCE) and stability of the PSCs. Further, we demonstrated the applicability of TPFB doping to other triphenylamine-based HTLs. Spectroscopic characterizations reveal that TPFB doping results in significantly improved charge transport and reduced recombination losses. Importantly, the TPFB-doped perovskite devices retained near 85% of the initial PCE after 1000 h of storage in the air, while the conventional LiTFSI-doped device dropped to 75%. Finally, we give insight into utilizing other similar molecular dopants such as fluorine-free triphenylborane and phosphorus-centered tris(pentafluorophenyl)phosphine (TPFP) by density functional theory analysis underscoring the significance of the central boron atom and fluorination in TPFB for the formation of Lewis acid-base adducts.

Although lanthanide double-decker complexes with hetero-macrocyclic ligands as functional luminescent and magnetic materials have promising properties, their inferior water solubility has negated their biomedical applications. Herein, four water-soluble homoleptic lanthanide ( Ln   =   Gd , Er , Yb and La ) sandwiches with diethylene-glycol-disubstituted porphyrins ( DD ) are reported, with their structures proven by both quantum chemical calculations and scanning tunneling microscopy. Our findings demonstrate that the near-infrared emission intensity and singlet oxygen ( 1 O 2 ) quantum yields of YbDD and GdDD in aqueous media are higher than those of the reported capped lanthanide monoporphyrinato analogues, YbN and GdN ; the brightness and luminescence lifetime in water of YbDD are greater than those of YbN . This work provides a new dimension for the future design and development of molecular theranostics-based water-soluble double-decker lanthanide bisporphyrinates., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest.

Titanium dioxide is a promising candidate for photocatalytic H 2 fuel production, and understanding water splitting on TiO 2 surfaces is vital toward explaining and improving the generation of H 2 . In this work, we electron irradiate anatase TiO 2 (101) at room temperature to create metastable surface oxygen vacancies in order to investigate their ability to dissociate H 2 O. Our scanning tunneling microscopy investigations suggest that the surface oxygen vacancies can dissociate H 2 O by forming bridging OH species. This claim is supported by theoretical calculations from the literature and our previously published spectroscopic measurements.