High Thermoelectric Performance in Supersaturated Solid Solutions and Nanostructured n‐Type PbTe–GeTe

Sb‐doped and GeTe‐alloyed n‐type thermoelectric materials that show an excellent figure of merit ZT in the intermediate temperature range (400–800 K) are reported. The synergistic effect of favorable changes to the band structure resulting in high Seebeck coefficient and enhanced phonon scattering by point defects and nanoscale precipitates resulting in reduction of thermal conductivity are demonstrated. The samples can be tuned as single‐phase solid solution (SS) or two‐phase system with nanoscale precipitates (Nano) based on the annealing processes. The GeTe alloying results in band structure modification by widening the bandgap and increasing the density‐of‐states effective mass of PbTe, resulting in significantly enhanced Seebeck coefficients. The nanoscale precipitates can improve the power factor in the low temperature range and further reduce the lattice thermal conductivity (κ_lat). Specifically, the Seebeck coefficient of Pb_0.988Sb_0.012Te–13%GeTe–Nano approaches ?280 µV K^?1 at 673 K with a low κ_lat of 0.56 W m^?1 K^?1 at 573 K. Consequently, a peak ZT value of 1.38 is achieved at 623 K. Moreover, a high average ZT_avg value of ≈1.04 is obtained in the temperature range from 300 to 773 K for n‐type Pb_0.988Sb_0.012Te–13%GeTe–Nano.     

Enhancement of Thermopower of TAGS‐85 High‐Performance Thermoelectric Material by Doping with the Rare Earth Dy

Enhancement of thermopower is achieved by doping the narrow‐band semiconductor Ag_6.52Sb_6.52Ge_36.96Te₅₀ (acronym TAGS‐85), one of the best p‐type thermoelectric materials, with 1 or 2% of the rare earth dysprosium (Dy). Evidence for the incorporation of Dy into the lattice is provided by X‐ray diffraction and increased orientation‐dependent local fields detected by ¹²⁵Te NMR spectroscopy. Since Dy has a stable electronic configuration, the enhancement cannot be attributed to 4f‐electron states formed near the Fermi level. It is likely that the enhancement is due to a small reduction in the carrier concentration, detected by ¹²⁵Te NMR spectroscopy, but mostly due to energy filtering of the carriers by potential barriers formed in the lattice by Dy, which has large both atomic size and localized magnetic moment. The interplay between the thermopower, the electrical resistivity, and the thermal conductivity of TAGS‐85 doped with Dy results in an enhancement of the power factor (PF) and the thermoelectric figure of merit (ZT) at 730 K, from PF = 28 μW cm^?1 K^?2 and ZT ≤ 1.3 in TAGS‐85 to PF = 35 μW cm^?1 K^?2 and ZT ≥ 1.5 in TAGS‐85 doped with 1 or 2% Dy for Ge. This makes TAGS‐85 doped with Dy a promising material for thermoelectric power generation.     

Enhanced Thermoelectric Performance in GeTe by Synergy of Midgap state and Band Convergence

The good co-existence of midgap state and valence band degeneracy is realized in Bi-alloyed GeTe through the In-Cd codoping to play different but complementary roles in the valence band structure modification. In doping induces midgap state and results in a considerably improved Seebeck coefficient near room temperature, while Cd doping significantly increases the Seebeck coefficient in the mid-high temperature region by promoting the valence band convergence. The synergistic effects obviously increase the density of state effective mass from 1.39 to 2.65 m₀, and the corresponding carrier mobility still reaches 34.3 cm² V⁻¹ s⁻¹ at room temperature. Moreover, the Bi-In-Cd co-alloying introduces various phonon scattering centers including nanoprecipitates and strain field fluctuations and suppresses the lattice thermal conductivity to a rather low value of 0.56 W m⁻¹ K⁻¹ at 600 K. As a result, the Ge_0.89Bi_0.06In_0.01Cd_0.04Te sample obtains excellent thermoelectric properties of zT_max ≈2.12 at 650 K and zT_avg ≈1.43 between 300 and 773 K. This study illustrates that the thermoelectric performance of GeTe can be optimized in a wide temperature range through the synergy of midgap state and valence band convergence.     

Enhanced Thermoelectric Performance in 18‐Electron Nb0.8CoSb Half‐Heusler Compound with Intrinsic Nb Vacancies

Typical 18‐electron half‐Heusler compounds, ZrNiSn and NbFeSb, are identified as promising high‐temperature thermoelectric materials. NbCoSb with nominal 19 valence electrons, which is supposed to be metallic, is recently reported to also exhibit thermoelectric properties of a heavily doped n‐type semiconductor. Here for the first time, it is experimentally demonstrated that the nominal 19‐electron NbCoSb is actually the composite of 18‐electron Nb_0.8+δCoSb (0 ≤ δ < 0.05) and impurity phases. Single‐phase Nb_0.8+δCoSb with intrinsic Nb vacancies, following the 18‐electron rule, possesses improved thermoelectric performance, and the slight change in the content of Nb vacancies has a profound effect on the thermoelectric properties. The carrier concentration can be controlled by varying the Nb deficiency, and the optimization of the thermoelectric properties can be realized within the narrow pure phase region. Benefiting from the elimination of impurity phases and the optimization of carrier concentration, thermoelectric performance is remarkably enhanced by ≈100% and a maximum zT of 0.9 is achieved in Nb_0.83CoSb at 1123 K. This work expands the family of half‐Heusler thermoelectric materials and opens a new avenue for searching for nominal 19‐electron half‐Heusler compounds with intrinsic vacancies as promising thermoelectric materials.     

Off-Centering of Ge Atoms in GeBi2Te4 and Impact on Thermoelectric Performance

The crystal structure and transport properties of GeBi₂Te₄ are investigated as a layered compound with potential applications as thermoelectric materials. A disordered arrangement of Ge and Bi atoms in a septuple-layer structure is discovered through synchrotron radiation X-ray diffraction and transmission electron microscopy. Neutron pair distribution function analysis revealed the presence of discordant Ge atoms with an off-centering distance of 0.12 Å at 300 K. The thermal conductivity of GeBi₂Te₄ is very low due to the strong phonon scattering. This is a result of the three Einstein local oscillators coupled with the disordered arrangement of atoms. This study also explores further the structural characteristics of these materials and their associated phonon scattering processes. The effect of Sb substitution for Ge on the electrical transport properties of the sample is profound, resulting in a change from p-type to n-type conduction. An enhanced thermoelectric figure of merit (ZT) of 0.45 at 523 K in the in-plane direction is obtained. This research provides valuable insights into the crystal structure and transport properties of GeBi₂Te₄, showcasing its promising role as a thermoelectric material with potential for near-room-temperature applications.     

Rational Manipulation of Epitaxial Strains Enabled Valence Band Convergence and High Thermoelectric Performances in Mg3Sb2 Films

Strain engineering is demonstrated to effectively regulate the functionality of materials, such as thermoelectric, ferroelectric, and photovoltaic properties. As the straightforward approach of strain engineering, epitaxial strain is usually proposed for rationally manipulating the electronic structure and performances of thermoelectric materials, but has rarely been verified experimentally. In this study, tunable and large epitaxial strains are demonstrated, as well as the resulting valence band convergence can be achieved in the Mg₃Sb₂ epi-films with the choice of substrates. The large epitaxial strains up to 8% in Mg₃Sb₂ films represent one of the most striking results in strain engineering. The angle-resolved photoemission spectroscopy measurements and the theoretical calculations reveal the vital role of epitaxial strain in tuning the crystal field splitting and the band structure of Mg₃Sb₂. Benefiting from the appropriate manipulation of the crystal field effect via in-plane compressive strain, the valence band convergence is unambiguously discovered in the strained Mg₃Sb₂ film grown on InP(111) substrate. As a result, a state-of-the-art thermoelectric power factor of 0.94 mWm⁻¹K⁻² is achieved in the strain-engineered Mg₃Sb₂ film, well exceeding that of the strain-relaxed Mg₃Sb₂. The work paves the way for effectively manipulating epitaxial strain and band convergence for Mg₃Sb₂ and other thermoelectric films.     

Atomic Disorders Induced by Silver and Magnesium Ion Migrations Favor High Thermoelectric Performance in α‐MgAgSb‐Based Materials

Thermoelectric devices can directly convert thermal energy to electricity or vice versa with the efficiency being determined by the materials’ dimensionless figure of merit (ZT). Since the revival of interests in the last decades, substantial achievements have been reached in search of high‐performance thermoelectric materials, especially in the high temperature regime. In the near‐room‐temperature regime, MgAgSb‐based materials are recently obtained with ZT ≈ 0.9 at 300 K and ≈1.4 at 525 K, as well as a record high energy conversion efficiency of 8.5%. However, the underlying mechanism responsible for the performance in this family of materials has been poorly understood. Here, based on structure refinements, scanning transmission electron microscopy (STEM), NMR experiments, and density function theory (DFT) calculations, unique silver and magnesium ion migrations in α‐MgAg_0.97Sb_0.99 are disclosed. It is revealed that the local atomic disorders induced by concurrent ion migrations are the major origin of the low thermal conductivity and play an important role in the good ZT in MgAgSb‐based materials.     

BiSbTe‐Based Nanocomposites with High ZT: The Effect of SiC Nanodispersion on Thermoelectric Properties

Thermoelectric materials have potential applications in energy harvesting and electronic cooling devices, and bismuth antimony telluride (BiSbTe) alloys are the state‐of‐the‐art thermoelectric materials that have been widely used for several decades. It is demonstrated that mixing SiC nanoparticles into the BiSbTe matrix effectively enhances its thermoelectric properties; a high dimensionless figure of merit (ZT) value of up to 1.33 at 373 K is obtained in Bi_0.3Sb_1.7Te₃ incorporated with only 0.4 vol% SiC nanoparticles. SiC nanoinclusions possessing coherent interfaces with the Bi_0.3Sb_1.7Te₃ matrix can increase the Seebeck coefficient while increasing the electrical conductivity, in addition to its effect of reducing lattice thermal conductivity by enhancing phonon scattering. Nano‐SiC dispersion further endows the BiSbTe alloys with better mechanical properties, which are favorable for practical applications and device fabrication.     

High Thermoelectric Performance in the Wide Band‐Gap AgGa1‐xTe2 Compounds: Directional Negative Thermal Expansion and Intrinsically Low Thermal Conductivity

A deficiency of Ga in wide band‐gap AgGa_1‐xTe₂ semiconductors (1.2 eV) can be used to optimize the electrical transport properties and reduce the thermal conductivity to achieve ZT > 1 at 873 K. First‐principles density functional theory calculations and a Boson peak observed in the low temperature heat capacity data indicate the presence of strong coupling between optical phonons with low frequency and heat carrying acoustical phonons, resulting in a depressed maximum of Debye frequency in the first Brillouin zone and low phonon velocities. Moreover, the Ag? Te bond lengths and Te? Ag? Te bond angles increase with rising temperature, leading to a significant distortion of the [AgTe₄]^7? tetrahedra, but an almost unmodified [GaTe₄]^5? tetrahedra. This behavior results in lattice expansion in the ab‐plane and contraction along the c‐axis, corresponding to the positive and negative Gruneisen parameters in the phonon spectral calculations. This effect gives rise to the large anharmonic behavior of the lattice. These factors together with the low frequency vibrations of Ag and Te atoms in the structure lead to an ultralow thermal conductivity of 0.18 W m^?1 K^?1 at 873 K.     

Controlling Ambipolar Charge Transport in Isoindigo‐Based Conjugated Polymers by Altering Fluorine Substitution Position for High‐Performance Organic Field‐Effect Transistors

A molecular design strategy to achieve highly balanced ambipolar charge transport for donor–acceptor (D–A) isoindigo (IIG)‐based copolymer through systematic selection of fluorination positions is reported. To study fluorine substitution site effects on electronic and structural properties, two fluorinated IIG‐based copolymers (PIIG‐iFT2 and PIIG‐oFT2) are synthesized, which contain two fluorine atoms at the bithiophene (T2) inner and outer site and compare them with a nonfluorinated copolymer of IIG and T2 (PIIG‐T2) as the reference polymer. Fluorination at the outer site of T2 in PIIG‐oFT2 polymer effectively lowers molecular energy levels and increases molecular planarity more than fluorination at the T2 inner site. PIIG‐oFT2 organic field‐effect transistors show highly balanced ambipolar mobility, hole mobility (μ_h)/electron mobility (μ_e) = 1 by increasing electron mobility, whereas PIIG‐T2 (μ_h/μ_e = 9.0) and PIIG‐iFT2 (μ_h/μ_e = 2.4) exhibit unbalanced ambipolar transport. The ambipolar complementary‐like inverter is also demonstrated by simple one‐time coating of PIIG‐oFT2 with gain = 21.     

Very High Efficiency Orange‐Red Light‐Emitting Devices with Low Roll‐Off at High Luminance Based on an Ideal Host–Guest System Consisting of Two Novel Phosphorescent Iridium Complexes with Bipolar Transport

Two phosphorescent iridium complexes with bipolar transporting ability, namely FPPCA (500 nm) and BZQPG (600 nm), are synthesized and employed as an ideal host‐guest system for phosphorescent organic light emitting diodes (PHOLEDs).The devices give very high‐efficiency orange‐red emission from BZQPG with maximum external quantum efficiency (EQE or η_ext) of >27% and maximum power efficiency (PE or η_p) of >75 lm/W, and maintain high levels of 26% and 55 lm/W, 25% and 40 lm/W at high luminance of 1000 and 5000 cd m^?2, respectively, within a range of 8–15 wt% of BZQPG. The realization of such high and stable EL performance results from the coexistence of two parallel paths: i) effective energy transfer from host (FPPCA) to guest (BZQPG) and ii) direct exciton formation on the BZQPG emitter, which can alternately dominate the electrophosphorescent emission. This all‐phosphor doping system removes the charge‐injection barrier from the charge‐transport process to the emissive layer (EML) due to the inherent narrow E_g of both phosphors. Therefore, this ideal host–guest system represents a new design to produce PHOLEDs with high efficiency and low efficiency roll‐off using a simple device configuration.     

High Thermoelectric Performance in Sulfide‐Type Argyrodites Compound Ag8Sn(S1−xSex)6 Enabled by Ultralow Lattice Thermal Conductivity and Extended Cubic Phase Regime

Argyrodites with a general chemical formula of A₈BC₆ are known for complex phase transitions, ultralow lattice thermal conductivity, and mixed electronic and ionic conduction. The coexistence of ionic conduction and promising thermoelectric performance have recently been reported in selenide and telluride argyrodites, but scarcely in sulfide argyrodites. Here, the thermoelectric properties of Ag₈Sn(S_1?xSe_x)₆ are reported. Specifically, Ag₈SnS₆ exhibits intrinsically ultralow lattice thermal conductivities of 0.61–0.31 W m^?1 K^?1 over the whole temperature range from 32 to 773 K due to distorted local crystal structure, relatively weak chemical bonding, rattler‐like Ag atoms, low‐lying optical modes, and dynamic disorder of Ag ions at high temperatures. Se doping shifts the orthorhombic–cubic phase transition from 457 K at x = 0 to 430 K at x = 0.10, thereby expanding the temperature range of the thermoelectrically favored cubic phase. A figure of merit zT value ≈ 0.80 is achieved at 773 K in Ag₈Sn(S_1?xSe_x)₆ (x = 0.03), the highest zT value reported in sulfide argyrodites. These results fill a knowledge gap of the thermoelectric study of argyrodites and contribute to a comprehensive understanding of the chemical bonding, lattice dynamics, and thermal transport of argyrodites.     

High‐Performance Thermally Stable Organic Phototransistors Based on PSeTPTI/PC61BM for Visible and Ultraviolet Photodetection

Phototransistors are three‐terminal photodetectors which usually have higher photosensitivity than photodiodes due to the presence of gate electrode. In this report, organic phototransistors (OPTs) based on a donor material, namely, poly{2,5‐selenophene‐alt‐2,8‐(4,10‐bis(2‐hexyldecyl))thieno[2′,3′:5,6]­pyrido[3,4‐g]thieno[3,2‐c]isoquinoline‐5,11(4H,10H)‐dione} (PSeTPTI), are fabricated and intensively studied. As unipolar p‐type organic semiconductor usually has plenty of electron traps in the bulk to impede electron transporting, most of photogenerated electrons will fill the traps in PSeTPTI and this process can prolong the response time. By introducing [6,6]‐phenyl C₆₁ butyric acid methyl ester on top, the p–n heterojunction can produce most of the photocurrent and eliminates the influence from the process of trapping electrons. This mechanism improves the photoresponsivity and response speed. Since ultraviolet (UV) detection is very important in some fields including military, aerospace, and biology, the OPTs are characterized under UV illumination besides the visible light and they present high sensitivity. Furthermore, organic semiconductors often have bad stability in harsh conditions and meanwhile some devices need to work in these environments. At high temperature even up to 200 °C, our OPTs can work normally and show very high stability, indicating the potential of the devices in applications of high‐temperature environments.     

High‐Performance n‐ and p‐Type Field‐Effect Transistors Based on Hybridly Surface‐Passivated Colloidal PbS Nanosheets

Colloidally synthesized nanomaterials are among the promising candidates for future electronic devices due to their simplicity and the inexpensiveness of their production. Specifically, colloidal nanosheets are of great interest since they are conveniently producible through the colloidal approach while having the advantages of two‐dimensionality. In order to employ these materials, according transistor behavior should be adjustable and of high performance. It is shown that the transistor performance of colloidal lead sulfide nanosheets is tunable by altering the surface passivation, the contact metal, or by exposing them to air. It is found that adding halide ions to the synthesis leads to an improvement of the conductivity, the field‐effect mobility, and the on/off ratio of these transistors by passivating their surface defects. Superior n‐type behavior with a field‐effect mobility of 248 cm² V^?1 s^?1 and an on/off ratio of 4 × 10⁶ is achieved. The conductivity of these stripes can be changed from n‐type to p‐type by altering the contact metal and by adding oxygen to the working environment. As a possible solution for the post‐Moore era, realizing new high‐quality semiconductors such as colloidal materials is crucial. In this respect, the results can provide new insights which helps to accelerate their optimization for potential applications.     

Towards High Efficiency and Low Roll‐Off Orange Electrophosphorescent Devices by Fine Tuning Singlet and Triplet Energies of Bipolar Hosts Based on Indolocarbazole/1, 3, 5‐Triazine Hybrids

Orange‐emitting phosphorescent organic light‐emitting diodes (PHOLEDs) are drawing more and more attention; however, high‐performance hosts designed for orange PHOLEDs are rare. Here, four indolocarbazole/1, 3, 5‐triazine hybrids are synthesized to optimize the singlet and triplet energies, as well as transporting properties, for ideal orange PHOLEDs. By introducing moieties with different electronegativity, a graded reduction of the singlet and triplet energies is achieved, resulting in minimum injection barrier and minimum energy loss. Besides, the charge transporting abilities are also tuned to be balanced on the basis of the bipolar features of those materials. The optimized orange PHOLED shows a maximum external quantum efficiency (EQE) of 24.5% and a power efficiency of 64 lm W^–1, both of which are among the best values for orange PHOLEDs. What is more, the efficiency roll‐off is extremely small, with an EQE of 24.4% at 1000 cd m^–2 and 23.8% at 10 000 cd m^–2, respectively, which is the lowest efficiency roll‐off for orange PHOLEDs to date, resulting in the highest EQE for orange PHOLEDs when the luminance is above 1000 cd m^–2. Besides the balanced charges, the small roll‐off is also attributed to the wide recombination zone resulting from the bipolar features of the hosts.     

High Tg Cyclic Olefin Copolymer Gate Dielectrics for N,N′‐Ditridecyl Perylene Diimide Based Field‐Effect Transistors: Improving Performance and Stability with Thermal Treatment

A novel application of ethylene‐norbornene cyclic olefin copolymers (COC) as gate dielectric layers in organic field‐effect transistors (OFETs) that require thermal annealing as a strategy for improving the OFET performance and stability is reported. The thermally‐treated N,N′‐ditridecyl perylene diimide (PTCDI‐C13)‐based n‐type FETs using a COC/SiO₂ gate dielectric show remarkably enhanced atmospheric performance and stability. The COC gate dielectric layer displays a hydrophobic surface (water contact angle = 95° ± 1°) and high thermal stability (glass transition temperature = 181 °C) without producing crosslinking. After thermal annealing, the crystallinity improves and the grain size of PTCDI‐C13 domains grown on the COC/SiO₂ gate dielectric increases significantly. The resulting n‐type FETs exhibit high atmospheric field‐effect mobilities, up to 0.90 cm² V^?1 s^?1 in the 20 V saturation regime and long‐term stability with respect to H₂O/O₂ degradation, hysteresis, or sweep‐stress over 110 days. By integrating the n‐type FETs with p‐type pentacene‐based FETs in a single device, high performance organic complementary inverters that exhibit high gain (exceeding 45 in ambient air) are realized.     

Employing Interfaces with Metavalently Bonded Materials for Phonon Scattering and Control of the Thermal Conductivity in TAGS‐x Thermoelectric Materials

The thermoelectric compound (GeTe)_x(AgSbTe₂)_1?x, in short (TAGS‐x), is investigated with a focus on two stoichiometries, i.e., TAGS‐50 and TAGS‐85. TAGS‐85 is currently one of the most studied thermoelectric materials with great potential for thermoelectric applications. Yet, surprisingly, the lowest thermal conductivity is measured for TAGS‐50, instead of TAGS‐85. To explain this unexpected observation, atom probe tomography (APT) measurements are conducted on both samples, revealing clusters of various compositions and sizes. The most important role is attributed to Ag₂Te nanoprecipitates (NPs) found in TAGS‐50. In contrast to the Ag₂Te NPs, the matrix reveals an unconventional bond breaking mechanism. More specifically, a high probability of multiple events (PME) of ≈60% is observed for the matrix by APT. Surprisingly, the PME value decreases abruptly to ≈20–30% for the Ag₂Te NPs. These differences can be attributed to differences in chemical bonding. The precipitates' PME value is indicative of normal bonding, i.e., covalent bonding with normal optical modes, while materials with this unconventional bond breaking found in the matrix are characterized by metavalent bonding. This implies that the interface between the metavalently bonded matrix and covalently bonded Ag₂Te NP is partly responsible for the reduced thermal conductivity in TAGS‐50.     

Shift of the Branching Point of the Side‐Chain in Naphthalenediimide (NDI)‐Based Polymer for Enhanced Electron Mobility and All‐Polymer Solar Cell Performance

The branching point of the side‐chain of naphthalenediimide (NDI)‐based conjugated polymers is systematically controlled by incorporating four different side‐chains, i.e., 2‐hexyloctyl (P(NDI1‐T)), 3‐hexylnonyl (P(NDI2‐T)), 4‐hexyldecyl (P(NDI3‐T)), and 5‐hexylundecyl (P(NDI4‐T)). When the branching point is located farther away from the conjugated backbones, steric hindrance around the backbone is relaxed and the intermolecular interactions between the polymer chains become stronger, which promotes the formation of crystalline structures in thin film state. In particular, thermally annealed films of P(NDI3‐T) and P(NDI4‐T), which have branching points far away from the backbone, possess more‐developed bimodal structure along both the face‐on and edge‐on orientations. Consequently, the field‐effect electron mobilities of P(NDIm‐T) polymers are monotonically increased from 0.03 cm² V⁻¹ s⁻¹ in P(NDI1‐T) to 0.22 cm² V⁻¹ s⁻¹ in P(NDI4‐T), accompanied by reduced activation energy and contact resistance of the thin films. In addition, when the series of P(NDIm‐T) polymers is applied in all‐polymer solar cells (all‐PSCs) as electron acceptor, remarkably high‐power conversion efficiency of 7.1% is achieved along with enhanced current density in P(NDI3‐T)‐based all‐PSCs, which is mainly attributed to red‐shifted light absorption and enhanced electron‐transporting ability.     

Effect of Spacer Length of Siloxane‐Terminated Side Chains on Charge Transport in Isoindigo‐Based Polymer Semiconductor Thin Films

A series of isoindigo‐based conjugated polymers (PII2F‐C_mSi, m = 3–11) with alkyl siloxane‐terminated side chains are prepared, in which the branching point is systematically “moved away” from the conjugated backbone by one carbon atom. To investigate the structure–property relationship, the polymer thin film is subsequently tested in top‐contact field‐effect transistors, and further characterized by both grazing incidence X‐ray diffraction and atomic force microscopy. Hole mobilities over 1 cm² V^?1 s^?1 is exhibited for all soluble PII2F‐C_mSi (m = 5–11) polymers, which is 10 times higher than the reference polymer with same polymer backbone. PII2F‐C₉Si shows the highest mobility of 4.8 cm² V^?1 s^?1, even though PII2F‐C₁₁Si exhibits the smallest π–π stacking distance at 3.379 Å. In specific, when the branching point is at, or beyond, the third carbon atoms, the contribution to charge transport arising from π–π stacking distance shortening becomes less significant. Other factors, such as thin‐film microstructure, crystallinity, domain size, become more important in affecting the resulting device's charge transport.