Calcination‐ and Etching‐Free Photolithography of Inorganic Phosphor Films Consisting of Rare Earth Ion Doped Nanoparticles on Plastic Sheets

It is demonstrated that patterned inorganic phosphor films consisting of rare earth ion doped nanoparticles (RE‐NPs) can be fabricated on plastic sheets using calcination‐ and etching‐free photolithography. Green up‐conversion luminescence and near‐infrared (NIR) fluorescence appears from the RE‐NPs that are prepared from Y₂O₃ doped with 1 mol% Er³⁺ and 0.85 mol% Yb³⁺. The diameter of the RE‐NPs is estimated to be about 300 nm using dynamic light scattering. Visible transmittance of the RE‐NP film fabricated by dip‐coating is more than 90%. Patterned RE‐NP films are obtained by dip‐coating the RE‐NPs on patterned photoresist films fabricated by UV exposure through a photomask, followed by selective removal of the photoresist. Optical, fluorescence, scanning electron, atomic force, and Kelvin probe force microscopies are used for the characterization of the patterned RE‐NP films. The present methodology enables fabrication of patterned RE‐NP films, not only on inorganic substrates but also on plastic sheets, with low cost and material consumption.     

Very low surface recombination velocity of crystalline silicon passivated by phosphorus‐doped a‐SicxNy:H(n) alloys

Hydrogenated and phosphorus‐doped amorphous silicon carbonitride films (a‐SiC_xN_y:H(n)) were deposited by plasma‐enhanced chemical vapor deposition (PECVD) on crystalline silicon surface in order to explore surface passivation properties. Very silicon‐rich films yielded effective surface recombination velocities at 1 sun‐illumination as low as 3 cm s⁻¹ and 2 cm s⁻¹ on 1 Ω cm p‐ and n‐type crystalline silicon substrates, respectively. In order to use them as anti‐reflection coating, we increased alternatively either the carbon or nitrogen content of these films. Also, a combination of passivation and antireflective films was analyzed. Finally, we explored the passivation stability under high‐temperature steps. Copyright © 2007 John Wiley & Sons, Ltd.     

High‐Performance Flexible Thermoelectric Devices Based on All‐Inorganic Hybrid Films for Harvesting Low‐Grade Heat

The fabrication of a flexible thermoelectric (TE) device that contains flexible, all‐inorganic hybrid thin films (p‐type single‐wall carbon nanotubes (SWCNTs)/Sb₂Te₃ and n‐type reduced graphene oxide (RGO)/Bi₂Te₃) is reported. The optimized power factors of the p‐type and n‐type hybrid thin films at ambient temperature are about 55 and 108 µW m^?1 K^?2, respectively. The high performance of these films that are fabricated through the combination of vacuum filtration and annealing can be attributed to their planar orientation and network structure. In addition, a TE device, with 10 couples of legs, shows an output power of 23.6 µW at a temperature gradient of 70 K. A prototype of an integrated photovoltaic‐TE (PV‐TE) device demonstrates the ability to harvest low‐grade “waste” thermal energy from the human body and solar irradiation. The flexible TE and PV‐TE device have great potential in wearable energy harvesting and management.     

Energetics of Donor‐Doping,Metal Vacancies,and Oxygen‐Loss in A‐Site Rare‐Earth‐Doped BaTiO3

The energetics of La‐doping in BaTiO₃ are reported for both (electronic) donor‐doping with the creation of Ti³⁺ cations and ionic doping with the creation of Ti vacancies. The experiments (for samples prepared in air) and simulations demonstrate that ionic doping is the preferred mechanism for all concentrations of La‐doping. The apparent disagreement with electrical conduction of these ionic doped samples is explained by subsequent oxygen‐loss, which leads to the creation of Ti³⁺ cations. Simulations show that oxygen‐loss is much more favorable in the ionic‐doped system than undoped BaTiO₃ due to the unique local structure created around the defect site. These findings resolve the so‐called “donor‐doping” anomaly in BaTiO₃ and explain the source of semiconductivity in positive temperature coefficient of resistance (PTCR) BaTiO₃ thermistors.     

Fabrication of MAPbBr3 Single Crystal p‐n Photodiode and n‐p‐n Phototriode for Sensitive Light Detection Application

In this study, MAPbBr₃ single crystal (MSC) p‐n perovskite homojunction photodiode and n‐p‐n phototriode are successfully fabricated through controlled incorporation of Bi³⁺ ions in solution. Optoelectronic analysis reveals that the photodiode shows typical photovoltaic behavior and the best photovoltaic performance can be achieved when the n‐type MSC is grown in 0.3% Bi³⁺ feed solution. The as‐assembled p‐n MSC photovoltaic detector displays obvious sensitivity to 520 nm illumination, with a high responsivity of up to 0.62 A W^‐1 and a specific detectivity of 2.16 × 10¹² Jones, which surpass many those of MSC photodetectors previously reported. Further performance optimization can be realized by constructing an n‐p‐n phototriode using the same growth method. The photocurrent magnification rate of the as‐fabricated n‐p‐n phototriode can reach a maximum value of 2.9 × 10³. Meanwhile, a higher responsivity of 14.47 A W^‐1, specific detectivity of 4.67 × 10¹³ Jones, and an external quantum efficiency of up to 3.46 × 10³ are achieved under an emitter–collector bias of 8 V. These results confirm that the present p‐n and n‐p‐n MSC homojunctions are promising device configurations, which may find potential application in future optoelectronic devices and systems.     

Morphological Evolution and Magnetic Property of Rare‐Earth‐Doped Hematite Nanoparticles: Promising Contrast Agents for T1‐Weighted Magnetic Resonance Imaging

A series of uniform rare‐earth‐doped hematite (α‐Fe₂O₃) nanoparticles are synthesized by a facile hydrothermal strategy. In a typical case of gadolinium (Gd)‐doped α‐Fe₂O₃, the morphology and chemical composition can be readily tailored by tuning the initial proportion of Gd³⁺/Fe³⁺ sources. As a result, the products are observed to be stretched into more elongated shapes with an increasing dopant ratio. As a benefit of such an elongated morphological feature and Gd³⁺ ions of larger effective magnetic moment than Fe³⁺, the doped product with the highest ratio of Gd³⁺ at 5.7% shows abnormal ferromagnetic features with a remnant magnetization of 0.605 emu g^?1 and a coercivity value of 430 Oe at 4 K. Density of states calculations also reveal the increase of total magnetic moment induced by Gd³⁺ dopant in α‐Fe₂O₃ hosts, as well as possible change of magnetic arrangement. As‐synthesized Gd‐doped α‐Fe₂O₃ nanoparticles are probed as contrast agents for T1‐weighted magnetic resonance imaging, achieving a remarkable enhancement effect for both in vitro and in vivo tests.     

Highly Efficient p‐i‐n and Tandem Organic Light‐Emitting Devices Using an Air‐Stable and Low‐Temperature‐Evaporable Metal Azide as an n‐Dopant

Cesium azide (CsN₃) is employed as a novel n‐dopant because of its air stability and low deposition temperature. CsN₃ is easily co‐deposited with the electron transporting materials in an organic molecular beam deposition chamber so that it works well as an n‐dopant in the electron transport layer because its evaporation temperature is similar to that of common organic materials. The driving voltage of the p‐i‐n device with the CsN₃‐doped n‐type layer and a MoO₃‐doped p‐type layer is greatly reduced, and this device exhibits a very high power efficiency (57 lm W^?1). Additionally, an n‐doping mechanism study reveals that CsN₃ was decomposed into Cs and N₂ during the evaporation. The charge injection mechanism was investigated using transient electroluminescence and capacitance–voltage measurements. A very highly efficient tandem organic light‐emitting diodes (OLED; 84 cd A^?1) is also created using an n–p junction that is composed of the CsN₃‐doped n‐type organic layer/MoO₃ p‐type inorganic layer as the interconnecting unit. This work demonstrates that an air‐stable and low‐temperature‐evaporable inorganic n‐dopant can very effectively enhance the device performance in p‐i‐n and tandem OLEDs, as well as simplify the material handling for the vacuum deposition process.     

Oxygen‐Vacancy‐Endurable Conductors with Enhanced Transparency Using Correlated 4d2 SrMoO3 Thin Films

Degenerately doped wide‐bandgap semiconductors, e.g., Sn‐doped In₂O₃, are the most conventional transparent conductors (TCs), but degradation of the TC performance by a doping bottleneck or instability due to oxygen vacancies is encountered. Recently, nondoped correlated metals have attracted great attention as a new strategy for developing next‐generation TCs. To date, most studies of this brand‐new type of TC have been biased toward 3d¹ vanadates. Here, compared with 3d¹ SrVO₃, it is found that the 4d² SrMoO₃ thin films show promising TC properties: higher ultraviolet–visible transmittance of 80% and extremely low resistivity of 100 µΩ cm at room temperature. This enhancement in the SrMoO₃ is ascribed to a p‐4d transition occurring at higher photon energy and a higher number of electrons in the outermost 4d orbitals, respectively. In addition, the TC properties of the correlated SrMoO₃ are resistive to oxygen vacancies. Using spectroscopic ellipsometry, it is found that this robustness is attributed to the lack of formation of defect states near the Fermi level, which is different from the observation in conventional TCs. Taken together, the correlated 4d² SrMoO₃ is appealing for next‐generation oxygen‐vacancy‐endurable conductors with enhanced transparency.     

Multivalent‐Ion‐Mediated Stabilization of Hydrogen‐Bonded Multilayers

Hydrogen‐bonding interactions are an important alternative to electrostatic interactions for assembling multilayer thin films of uncharged components. Herein, a new method is reported for rendering such films stable at pH values close to physiological conditions. Multilayer films based on hydrogen bonding are assembled by the alternate deposition of poly[(styrene sulfonic acid)‐co‐(maleic acid)] (PSSMA) and poly(N‐isopropylacrylamide) (PNiPAAm) at pH 2.5. The use of PSSMA results in multilayers that contain free styrene sulfonate groups, as these moieties do not interact with the PNiPAAm functional groups. Subsequent infiltration of a multivalent ion (Ce⁴⁺ or Fe³⁺) leads to an increase in the total film mass, with little impact on the film morphology, as determined by using atomic force microscopy. To examine the film stability, the resulting films have been exposed to elevated pH (7.1). While there is substantial swelling of the multilayers (25 % and 55 % for Ce⁴⁺‐ and Fe³⁺‐stabilized films, respectively), film loss is negligible. This provides a stark contrast with non‐stabilized films, which disassemble almost immediately upon exposure to pH 7.1. This method represents a simple and effective strategy for stabilizing hydrogen‐bonded structures non‐covalently. Further, the multivalent ions also render the films responsive to changes in the local redox environment, as demonstrated by film disassembly after exposure of Fe³⁺‐treated films to iodide solutions.     

Water‐Induced Phase Separation Forming Macrostructured Epitaxial Quartz Films on Silicon

Quartz has been widely used as a bulk material in optics, the microelectronic industry, and sensors. The nanostructuring and direct integration of oriented quartz crystals onto a semiconductor platform has proven to be challenging. However, here, a new approach is presented to integrate epitaxial quartz films with macroperforations within the range of 500 nm and 1 μm using chemical solution deposition. This method constitutes an appealing approach to develop piezoelectric mass sensors with enhanced resonance frequencies due to the thickness reduction. Perforated quartz films on (100)‐silicon are prepared from amorphous silica films deposited via dip‐coating and doped with metal cations that catalyze quartz crystallization. The metal cations are also active in the formation of the macroperforations, which arise due to a phase separation mechanism. Cationic surfactant–anion–metal cation assemblies stabilize droplets of water, creating an indentation in the hydrophilic silica matrix which remains after solvent evaporation. Many cations induce phase separation, including Li⁺, Na⁺, Sr²⁺, Mn²⁺, Fe²⁺/Fe³⁺, Ca²⁺, Ce³⁺ and La³⁺ but only the Sr²⁺ and Ca²⁺ cations in this series induce the epitaxial growth of α‐quartz films under the conditions studied. The combination of sol–gel chemistry and epitaxial growth opens new opportunities for the integration of patterned quartz on silicon.     

Large Nonclassical Electrostriction in (Y,Nb)‐Stabilized δ‐Bi2O3

Classical electrostriction, describing a second‐order electromechanical response of insulating solids, scales with elastic compliance, S, and inversely with dielectric susceptibility, ε. This behavior, first noted 20 years ago by Robert Newnham, is shown to apply to a wide range of electrostrictors including polymers, glasses, crystalline linear dielectrics, and relaxor ferroelectrics. Electrostriction in fluorite ceramics of (Y, Nb)‐stabilized δ‐Bi₂O₃ is examined with 16%–23% vacant oxygen sites. Given the values of compliance and dielectric susceptibility, the electrostriction coefficients are orders of magnitude larger than those expected from Newnham's scaling law. In ambient temperature nanoindentation measurements, (Y, Nb)‐stabilized δ‐Bi₂O₃ displays primary creep. These findings, which are strikingly similar to those reported for Gd‐doped ceria, support the suggestion that ion conducting ceramics with the fluorite structure, a large concentration of anion vacancies and anelastic behavior, may constitute a previously unknown class of electrostrictors.     

XBi4S7 (X = Mn,Fe): New Cost‐Efficient Layered n‐Type Thermoelectric Sulfides with Ultralow Thermal Conductivity

A new class of cost‐efficient n‐type thermoelectric sulfides with a layered structure is reported, namely MnBi₄S₇ and FeBi₄S₇. Theoretical calculations combined with synchrotron X‐ray/neutron diffraction analyses reveal the origin of their electronic and thermal properties. The complex low‐symmetry monoclinic crystal structure generates an electronic band structure with a mixture of heavy and light bands near the conduction band edge, as well as vibrational properties favorable for high thermoelectric performance. The low thermal conductivity can be attributed to the complex layered crystal structure and to the existence of the lone pair of electrons in Bi³⁺. This feature combined with the relatively high power factor lead to a figure of merit as high as 0.21 (700 K) in undoped MnBi₄S₇, making this material a promising n‐type candidate for low‐ and intermediate‐temperature thermoelectric applications.     

Flexible,Multifunctional, Magnetically Actuated Nanocomposite Films

Filler nanoparticles greatly enhance the performance of polymers and minimize filler content in the resulting nanocomposites. At the same time, they challenge the manufacturing of such nanocomposites by filler agglomeration and non‐uniform spatial distribution. Here, multifunctional nanocomposite films are made by capitalizing on flame‐synthesis of ceramic or metal filler nanoparticles followed by rapid, in situ deposition on sacrificial substrates, resulting in a filler film with controlled porosity. The polymer is then spin‐coated on the porous film that retained its stochastic but uniform structure, resulting in nanocomposites with homogeneous filler distribution and high filler‐loading. By sequential repetition of this procedure, sophisticated, multilayer, free‐standing, plasmonic‐ (Ag‐Fe₂O₃) and phosphorescent‐superparamagnetic (Y₂O₃:Eu³⁺‐ Fe₂O₃) actuators are made by precisely tuning the polymer thickness between each functional nanostructured layer. These actuators are quite flexible, have fast response times, and exhibit superior superparamagnetism due to their high filler content and homogeneous spatial distribution.     

Ti‐Doping to Reduce Conductivity in Bi0.85Nd0.15FeO3 Ceramics

In 2009, Karimi et al. reported that Bi_1‐xNd_xFeO₃ 0.15 ≤ x ≤ 0.25 exhibited a PbZrO₃ (PZ)‐like structure. These authors presented some preliminary electrical data for the PZ‐like composition but noted that the conductivity was too high to obtain radio‐frequency measurements representative of the intrinsic properties. In this study, Bi_0.85Nd_0.15Fe_1‐yTi_yO₃ (0 ≤ y ≤ 0.1) were investigated, in which Ti acted as a donor dopant on the B‐site. In contrast to the original study of Karimi et al., X‐ray diffraction (XRD) of Bi_0.85Nd_0.15FeO₃ revealed peaks which were attributed to a mixture of PZ‐like and rhombohedral structures. However, as the Ti (0 < y ≤ 0.05) concentration increased, the rhombohedral peaks disappeared and all intensities were attributed to the PZ‐like phase. For y = 0.1, broad XRD peaks indicated a significant decrease in effective diffracting volume. Electron diffraction confirmed that the PZ‐like phase was dominant for y ≤ 0.05, but for y = 0.1, an incommensurate structure was present, consistent with the broadened XRD peaks. The substitution of Fe³⁺ by Ti⁴⁺ decreased the dielectric loss at room temperature from >0.3 to <0.04 for all doped compositions, with a minimum (0.015) observed for y = 0.03. The decrease in dielectric loss was accompanied by a decrease in the room temperature bulk conductivity from ～1 mS cm^?1 to <1 μS cm^?1 and an increase in bulk activation energy from 0.29 to >1 eV. Plots of permittivity (?_r) versus temperature for 0.01 ≤ y ≤ 0.05 revealed a step rather than a peak in ?_r on heating at the same temperature determined for the antiferroelectric–paraelectric phase transition by differential scanning calorimetry. Finally, large electric fields were applied to all doped samples which resulted in a linear dependence of polarisation on the electric field similar to that obtained for PbZrO₃ ceramics under equivalent experimental conditions.     

Polaron Transport and Thermoelectric Behavior in La‐Doped SrTiO3 Thin Films with Elemental Vacancies

The electrodynamic properties of La‐doped SrTiO₃ thin films with controlled elemental vacancies are investigated using optical spectroscopy and thermopower measurement. In particular, a correlation between the polaron formation and thermoelectric properties of the transition metal oxide (TMO) thin films is observed. With decreasing oxygen partial pressure during the film growth (P(O₂)), a systematic lattice expansion is observed along with the increased elemental vacancy and carrier density, experimentally determined using optical spectroscopy. Moreover, an absorption in the mid‐infrared photon energy range is found, which is attributed to the polaron formation in the doped SrTiO₃ system. Thermopower of the La‐doped SrTiO₃ thin films can be largely modulated from –120 to –260 μV K^?1, reflecting an enhanced polaronic mass of ≈3 < m _polron/m < ≈4. The elemental vacancies generated in the TMO films grown at various P(O₂) influences the global polaronic transport, which governs the charge transport behavior, including the thermoelectric properties.     

High‐efficiency Sb2S3‐based hybrid solar cell at low light intensity: cell made of synthesized Cu and Se‐doped Sb2S3

Cu‐doped (as p‐doped) and Se‐doped (as n‐doped) Sb₂S₃ were synthesized from undoped Sb₂S₃ using a newly developed technique, simple colloidal synthesis method. X‐ray diffraction measurements detected no peaks related to any of the Cu and Se compounds in Cu and Se‐doped samples. Energy dispersive X‐ray analysis, however, confirmed the presence of Cu and Se ions in the doped samples. Diffuse reflectance spectroscopy revealed the optical band gap energy changes because of doping effect, as reported for both the p‐type and the n‐type material. The valence‐band X‐ray photoelectron spectroscopy data showed a significant shift in the valence band to higher (Se‐doped; +0.53 eV) and a shift to lower (Cu‐doped; −0.41 eV) binding energy, respectively, when compared with the undoped sample. We report here on an inexpensive solar cell designed and made entirely of a synthesized material (indium tin oxide/p‐doped Sb₂S₃ + polyaniline (PANI)/amorphous/undoped Sb₂S₃ + PANI/n‐doped Sb₂S₃ + PANI/PANI/electrolyte (0.5 M KI + 0.05 M I₂)/Al). The cell has a high efficiency of 8% to 9% at a very low light intensity of only 5% sun, which makes it particularly suitable for indoor applications. As found, the cell performance at the intensity of 5% sun is governed by high shunt resistance (R_SH) only, which satisfies standard testing conditions. At higher light intensities (25% sun), however, the cell exhibits lower but not insignificant efficiency (around 2%) governed by both the series (R_S) and the R_SH. Minimal permeability in the UV region (up to 375 nm) and its almost constant value in the visible and the NIR region at low light intensity of 5% sun could be the reasons for higher cell efficiency. Copyright © 2015 John Wiley & Sons, Ltd.     

Structural and Spectroscopic Characterization of Nominal Yb3+:Ca8La2(PO4)6O2 Oxyapatite Single Crystal Fibers Grown by the Micro‐Pulling‐Down Method

Yb‐doped Ca₈La₂(PO₄)₆O₂ (CLPA) single crystals with the apatite‐type structure and having <0001> orientation were grown by the micro‐pulling‐down (μ‐PD) method. The apatite structure is represented by the monophased field of Ca₈(La_2–xYb_x)‐(PO₄)₆O₂ (CLYPA) where it is assumed that 2 Ca²⁺ sites are substituted by La³⁺ and Yb³⁺ cations. Its monophased range was found to be from x = 0.0 to 0.2. The segregation of Yb³⁺ in CLPA single crystals and the maximum Yb³⁺ concentration are discussed. The crystallinity was studied using X‐ray rocking curve analysis. Absorption, emission and fluorescence decay studies of Yb³⁺ ions in CLPA were also carried out both at low temperature and room temperature. Spectroscopic data reveal Yb³⁺ ion occupation within different crystallographic sites of the apatite‐type structure. The potential for a diode‐pumped Yb³⁺ laser is evaluated.     

The Role of Point Defects in the Mechanical Behavior of Doped Ceria Probed by Nanoindentation

The influence of dopant size and oxygen vacancy concentration on the room temperature elastic modulus and creep rate of ceria doped with Pr⁴⁺, Pr³⁺, Lu³⁺, and Gd³⁺, is investigated using a nanoindentation technique. Measurements are conducted with both fast (15 mN s^?1) and slow (0.15 mN s^?1) loading modes, including a load‐hold stage at 150 mN of 8 s and 30 s, respectively. Based on the data obtained using the fast loading mode, it is found that: 1) the dopant size is a primary determinant of the elastic modulus—the larger dopants (Pr³⁺ and Gd³⁺) produce lower unrelaxed moduli which are independent of the oxygen vacancy concentration. 2) The rearrangement of point defects is the major source of room temperature creep observed during load‐hold. Pr³⁺‐ and Gd³⁺‐doped ceria display the higher creep rates: due to their large size, they repel oxygen vacancies (V_O), thereby promoting the formation of O₇–Ce_Ce–V_O complexes that are capable of low temperature rearrangement. Lower creep rates are observed for Pr⁴⁺‐ and Lu³⁺‐doped ceria: the former has no vacancies and the latter, immobile vacancies. 3) Nanoindentation is a practical technique for identifying materials with labile point defects, which may indicate useful functionality such as high ionic conductivity, large electrostriction, and inelasticity.     

Atomistic Study of a CaTiO3‐Based Mixed Conductor: Defects,Nanoscale Clusters,and Oxide‐Ion Migration

Mixed oxide‐ion and electronic conductivity can be exploited in dense ceramic membranes for controlled oxygen separation as a means of producing pure oxygen or integrating with catalytic oxidation. Atomistic simulation has been used to probe the energetics of defects, dopant‐vacancy association, nanoscale cluster formation, and oxide‐ion transport in mixed‐conducting CaTiO₃. The most favorable energetics for trivalent dopant substitution on the Ti site are found for Mn³⁺ and Sc³⁺. Dopant‐vacancy association is predicted for pair clusters and neutral trimers. Low binding energies are found for Sc³⁺ in accordance with the high oxide‐ion conductivity of Sc‐doped CaTiO₃. The preferred location for Fe⁴⁺ is in a hexacoordinated site, which supports experimental evidence that Fe⁴⁺ promotes the termination of defect chains and increases disorder. A higher oxide‐ion migration energy for a vacancy mechanism is predicted along a pathway adjacent to an Fe³⁺ ion rather than Fe⁴⁺ and Ti⁴⁺, consistent with the higher observed activation energies for ionic transport in reduced CaTi(Fe)O_3–δ.     

Control of Ambipolar and Unipolar Transport in Organic Transistors by Selective Inkjet‐Printed Chemical Doping for High Performance Complementary Circuits

The selective tuning of the operational mode from ambipolar to unipolar transport in organic field‐effect transistors (OFETs) by printing molecular dopants is reported. The field‐effect mobility (μ_FET) and onset voltage (V_on) of both for electrons and holes in initially ambipolar methanofullerene [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) OFETs are precisely modulated by incorporating a small amount of cesium fluoride (CsF) n‐type dopant or tetrafluoro‐tetracyanoquinodimethane (F4‐TCNQ) p‐type dopant for n‐channel or p‐channel OFETs either by blending or inkjet printing of the dopant on the pre‐deposited semiconductor. Excess carriers introduced by the chemical doping compensate traps by shifting the Fermi level (E_F) toward respective transport energy levels and therefore increase the number of mobile charges electrostatically accumulated in channel at the same gate bias voltage. In particular, n‐doped OFETs with CsF show gate‐voltage independent Ohmic injection. Interestingly, n‐ or p‐doped OFETs show a lower sensitivity to gate‐bias stress and an improved ambient stability with respect to pristine devices. Finally, complementary inverters composed of n‐ and p‐type PCBM OFETs are demonstrated by selective doping of the pre‐deposited semiconductor via inkjet printing of the dopants.