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.

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 performance of state-of-the-art OPVs. Adding DQ in ternary bulk-heterojunction (BHJ) cells based of PM6:Y6:PC 71 BM is found to consistently increase their power conversion efficiency (PCE) from 16.7 to 17.4%. Analyses of materials and devices reveal that DQ acts as n-type dopant and morphology modifier for the BHJ leading to observable changes in its surface topography. The resulting n-doped BHJs exhibit higher optical absorption coefficients, balanced ambipolar transport, longer carrier lifetimes and suppressed bimolecular recombination, which are ultimately responsible for the increased PCE. The use of DQ was successfully extended to OPVs based on PM6:BTP-eC9:PC 71 BM for which a maximum PCE of 18.3% (uncertified) was achieved. Our study highlights DQ as a promising dopant for application in next generation organic solar cells.

Self-assembled monolayers (SAMs) based on Br-2PACz ([2-(3,6dibromo-9H-carbazol-9-yl)ethyl]phosphonic acid) 2PACz ethyl]phosphonic acid) and ethyl]phosphonic acid) molecules were investigated as hole-extracting interlayers in organic photovoltaics (OPVs). The highest occupied molecular orbital (HOMO) energies of these SAMs were measured at À 6.01 and À 5.30 eV for Br-2PACz and MeO-2PACz, respectively, and found to induce significant changes in the work function (WF) of indium-tin-oxide (ITO) electrodes upon chemical functionalization. OPV cells based on PM6 (poly [(2,6-(4,8-bis(5-(2-ethylhexyl-3- ([6,6]-phenyl-C71-bu-tyric acid methyl ester) using ITO/Br-2PACz anodes exhibited a maximum power conversion efficiency (PCE) of 18.4 %, outperforming devices with ITO/MeO-2PACz (14.5 %) and ITO/poly (3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PE-DOT : PSS) (17.5 %). The higher PCE was found to originate from the much higher WF of ITO/Br-2PACz (À 5.81 eV) compared to ITO/MeO-2PACz (4.58 eV) and ITO/PEDOT : PSS (4.9 eV), resulting in lower interface resistance, improved hole transport/extraction, lower trap-assisted recombination, and longer carrier lifetimes. Importantly, the ITO/Br-2PACz electrode was chemically stable, and after removal of the SAM it could be recycled and reused to construct fresh OPVs with equally impressive performance.

(1 of 37)high mobility (µ) (even in amorphous phase), wide bandgap (transparent in the visible range), and the ability to be controllably doped. Importantly, they can be grown into thin films and various nanostructures with different scalable deposition techniques, including vacuum-based methods such as physical vapor deposition (PVD) [7,8] and chemical vapor deposition (CVD) [9] as well as solution-based processes such as spray [10] and spin coating. [11] Moreover, the resulting layers can be easily patterned using standard fabrication procedures and as such can be integrated into state-of-the-art processes for (opto)electronic applications. The above-mentioned capabilities have led to a plethora of applications such as switching backplanes for displays, transparent and flexible electronics, integrated circuits (ICs), photovoltaics (PVs), organic light-emitting diodes (OLEDs), capacitors, batteries, photocatalytic devices, electrochromics and memory devices, to name but a few. [8,[12][13][14] Because of their ability to be doped, their electronic properties can be tuned from dielectrics to semiconductors and conductors. This characteristic versatility has recently been exploited to stretch the range of their applications to new technological sectors, such as plasmonics in the near infrared and midinfrared spectral ranges. [12,15] One of the driving applications of metal oxides is in thinfilm transistors (TFTs) for large area electronics such as current driven optical displays and ICs. Following the early demonstrations, [16] most effort focused on the fabrication and processing of metal oxides TFTs paying particular attention to the device performance and applications. [1,5,6,17] Especially when processed over large areas, as in the case for display applications, the complexity to precisely control the device reliability and reproducibility becomes a challenging aspect of any TFT technology. To that respect, solution-based techniques progressed rapidly due to their lower cost and higher throughput compared to vacuum-based techniques. In both cases, the metal-oxide deposition has so far been limited to high processing temperatures (>250 °C) (Figure 1a) which renders the technology incompatible with inexpensive, temperature-sensitive substrates such as polymers, the material class of choice for various high throughput manufacturing techniques such as roll-to-roll (R2R) and sheet-to-sheet (S2S)Over the past few decades, significant progress has been made in the field of photonic processing of electronic materials using a variety of light sources. Several of these technologies have now been exploited in conjunction with emerging electronic materials as alternatives to conventional hightemperature thermal annealing, offering rapid manufacturing times and compatibility with temperature-sensitive substrate materials among other potential advantages. Herein, recent advances in photonic processing paradigms of metal-oxide thin-film transistors (TFTs) are presented with particular emphasis on the use of various light sour...

Solution‐processed metal oxide thin‐film transistors (TFTs) represent a promising technology for applications in existing but also emerging large‐area electronics. However, high process temperatures and lengthy annealing times represent two remaining technical challenges. Different approaches aiming to address these challenges have been proposed but progress remains modest. Here, the development of high electron mobility metal oxide TFTs based on photonically converted Al2O3/ZrO2 and In2O3/ZnO bilayers acting as the high‐k dielectric and electron‐transporting channel, respectively is described. Sequential solution‐phase deposition and photonic processing lead to low substrate temperature (<200 °C) while minimizing the overall process time to less than 60 s without compromising the quality of the formed layers. The bilayer Al2O3/ZrO2 dielectric exhibits low leakage current density (10−6 A cm−2 at 1 MV cm−1), high geometric capacitance (≈120 nF cm−2) and breakdown electric field of ≈1 MV cm−1. Combining Al2O3/ZrO2 with a photonically converted In2O3/ZnO heterojunction channels, results in TFTs with high electron mobility (19 cm2 V−1 s−1), low operation voltage (≤2 V), high current on/off ratio (>106), and low subthreshold swing (108 mV dec−1), that can be manufactured even onto thermally sensitive polymer substrates. The work is a significant step toward all‐photonic processed metal oxide electronics.