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Accelerating the shift towards renewable materials and sustainable processes for printed organic electronic devices is crucial for a green circular economy. Currently, the fabrication of organic devices with competitive performances is linked to toxic petrochemical-based solvents with considerable carbon emissions. Here we show that terpene solvents obtained from renewable feedstocks can replace non-renewable environmentally hazardous solvent counterparts in the production of highly efficient organic photovoltaics (OPVs) light-emitting diodes (OLEDs) and field-effect transistors (OFETs) with on-par performances. Using a Hansen solubility ink formulation framework, we identify various terpene solvent systems and investigate effective film formation and drying mechanisms required for optimal charge transport. This approach is universal for state-of-the-art materials in OPVs, OLEDs and OFETs. We created an interactive library for green solvent selections and made it publicly available through the OMEGALab website. As potential carbon-negative solvents, terpenes open a unique and universal approach towards efficient, large-area and stable organic electronic devices.

Molecular doping is the key to enabling organic electronic devices, however, the design strategies to maximize doping efficiency demands further clarity and comprehension. Previous reports focus on the effect of the side chains, but the role of the backbone is still not well understood. In this study, we synthesize a series of NDI-based copolymers with bithiophene, vinylene, and acetylenic moieties (P1G, P2G, and P3G, respectively), all containing branched triethylene glycol side chains. Using computational and experimental methods, we explore the impact of the conjugated backbone using three key parameters for doping in organic semiconductors: energy levels, microstructure, and miscibility. Our experimental results show that P1G undergoes the most efficient n-type doping owed primarily to its higher dipole moment, and better host–dopant miscibility with N-DMBI. In contrast, P2G and P3G possess more planar backbones than P1G, but the lack of long-range order, and poor host–dopant miscibility limit their doping efficiency. Our data suggest that backbone planarity alone is not enough to maximize the electrical conductivity (σ) of n-type doped organic semiconductors, and that backbone polarity also plays an important role in enhancing σ via host–dopant miscibility. Finally, the thermoelectric properties of doped P1G exhibit a power factor of 0.077 μW m−1 K−2, and ultra-low in-plane thermal conductivity of 0.13 W m−1K−1 at 5 mol% of N-DMBI, which is among the lowest thermal conductivity values reported for n-type doped conjugated polymers., Molecular doping is the key to enabling organic electronic devices, however, the design strategies to maximize doping efficiency demands further clarity and comprehension.

This publication is supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. OSR-CRG2018-3737.

Molecular doping is a powerful tool to tune the thermoelectric (TE) properties of solution-processed semiconductors. In this work, we prepared a binary composite and effectively doped both of its constituents, that is, naphthalene diimide-bithiophene copolymers (PNDI2OD-T2) and single-walled carbon nanotubes (SWCNTs), by a 1

In recent years, most of the works on p-type organic thermoelectrics have focused on improving the thermoelectric properties of poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) ...

Most studies to date on SnSe thermal transport are focused on single crystals and polycrystalline pellets that are obtained using high-temperature processing conditions and sophisticated instruments. The effects of using sub-10 nm-size SnSe nanocrystals on the thermal transport and thermoelectric properties have not been studied to the best of our knowledge. Here, we report the synthesis of sub-10 nm colloidal surfactant-free SnSe NCs at a relatively low temperature (80 °C) and investigate their thermoelectric properties. Pristine SnSe NCs exhibit p-type transport but have a modest power factor of 12.5 μW m−1 K−2 and ultralow thermal conductivity of 0.1 W m−1 K−1 at 473 K. Interestingly, the one-step post-synthesis treatment of NC film with methylammonium iodide can switch the p-type transport of the pristine film to n-type. The power factor improved significantly to 20.3 μW m−1 K−2, and the n-type NCs show record ultralow thermal conductivity of 0.14 W m−1 K−1 at 473 K. These surfactant-free SnSe NCs were then used to fabricate flexible devices that show superior performance to rigid devices. After 20 bending cycles, the flexible device shows a 34% loss in the power factor at room temperature (295 K). Overall, this work demonstrates p- and n-type transport in SnSe NCs via the use of simple one-step post-synthesis treatment, while retaining ultralow thermal conductivity.

The choice of interfacial materials and their properties play a critical role in determining solar cell performance and stability. For compatibility with roll-to-roll printing, it is desirable to develop stable cathode interface layers (CILs) that can be processed over the photoactive layer using orthogonal solvents. In this study, an n-type naphthalene diimide core and oligo (ethylene glycol) side-chain-based conjugated polymer is reported as a universal, efficient CIL for organic and perovskite photovoltaics. Besides good thermal stability and easy processing in alcohol/water, the new CIL is found to possess electron transport properties with an electrical conductivity of 2.3 x 10(-6) S cm(-1), enabling its use as a CIL with a film thickness of up to similar to 35(+/- 2) nm. Utilizing the new CIL, 16% power conversion efficiency (PCE) is achieved for organic solar cells (OSCs) based on the PM6-Y6 photoactive layer (8.9% PCE for no CIL and 15.1% with state-of-the-art CIL, PDINO), and perovskite solar cells from methylammonium lead iodide yielded a PCE of 17.6%. Compared to the reference devices, the new CIL reduced trap-assisted carrier recombination and increased the built-in potential by 80 mV, simultaneously enhancing all photovoltaic parameters. Moreover, new CIL based devices had better photostability with no burn-in losses.

There 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 approximate to 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 mu W 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. Funding Agencies|STW/NWOTechnologiestichting STWNetherlands Organization for Scientific Research (NWO) [VIDI 13476]; China Scholarship CouncilChina Scholarship Council; Center for Information Technology of the University of Groningen; Swedish Research CouncilSwedish Research Council [2016-03979]; Olle Engkvists Stiftelse [204-0256]; Advanced Functional Materials center at LiU [2009 00971]; King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) [OSR-CRG2018-3737]; NWO Exact and Natural Sciences [2020/ENW/00852342]

A.M. has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 844655 (SMOLAC). This publication is based on work supported by the KAUST Office of Sponsored Research (OSR) under award nos. OSR-2018-CARF/CCF-3079 and OSR-CRG2018-3746. D.A. also acknowledges the KAUST PSE Division for hosting his sabbatical in the framework of the Division's Visiting Faculty program. D.A. acknowledges funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) for financial support through the collaborative research centers TRR 146, SPP 2196, and grant number 460766640. K.-H.L. acknowledges the financial support from the Swiss NSF Early Postdoc Mobility fellowship (grant no. P2ELP2_195156). The authors thank Kostas Daoulas, Leanne Paterson, and Naoimi Kinaret for fruitful discussions and proof-reading of the manuscript. Open access funding enabled and organized by Projekt DEAL.

J.T. would like to thank Dr. Xin Song for valuable discussions surround organic photovoltaic device fabrication. This publication is based upon work supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under award numbers “KAUST OSR-CARF URF/1/3079-33-01,” “OSR-2018-CARF/CCF-3079,” and “OSR-2018-KAUST-KAU Initiative-3902.”

D.C. and D.B. thank Xin Song, Nicola Gasparini, Joel Throughton, and Stefan Schlisske for fruitful discussions.

E.B. and D.C. contributed equally to this work. E.B. and D.C. thank Xin Song for fruitful discussions for device optimization and Khulud Almasabi for assistance with the mechanical profilometer. The photograph Figure 1b and the TOC photographs were realized by Anastasia Khrenova, Specialist, Scientific Images and Design, at King Abdullah University of Science and Technology (KAUST).

The recent re‐emergence of halide perovskites has received escalating interest for optoelectronic applications. In addition to photovoltaics, the multifunctional nature of halide perovskites has led to diverse applications. The ultralow thermal conductivity coupled with decent mobility and charge carrier tunability led to the prediction of halide perovskites as a possible contender for future thermoelectrics. Herein, recent advances in thermal transport of halide perovskites and their potentials and challenges for thermoelectrics are reviewed. An overview of the phonon behavior in halide perovskites, as well as the compositional dependency is analyzed. Understanding thermal transport and knowing the thermal conductivity value is crucial for creating effective heat dissipation schemes and determining other thermal‐related properties like thermo‐optic coefficients, hot‐carrier cooling, and thermoelectric efficiency. Recent works on halide perovskite‐based thermoelectrics together with theoretical predictions for their future viability are highlighted. Also, progress on modulating halide perovskite‐based thermoelectric properties using light and chemical doping is discussed. Finally, strategies to overcome the limiting factors in halide perovskite thermoelectrics and their prospects are emphasized., Halide perovskites exhibit ultralow thermal conductivity and intriguing phononic behavior. This work elucidates the thermal transport behavior in halide perovskites and highlights their potentials and challenges for thermoelectric application.

This is the peer reviewed version of the following article: Low-Temperature-Processed Colloidal Quantum Dots as Building Blocks for Thermoelectrics, which has been published in final form at https://onlinelibrary.wiley.com/doi/epdf/10.1002/aenm.201803049 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.