Hole‐transporting materials (HTMs) play a critical role in realizing efficient and stable perovskite solar cells (PVSCs). Considering their capability of enabling PVSCs with good device reproducibility and long‐term stability, high‐performance dopant‐free small‐molecule HTMs (SM‐HTMs) are greatly desired. However, such dopant‐free SM‐HTMs are highly elusive, limiting the current record efficiencies of inverted PVSCs to around 19%. Here, two novel donor–acceptor‐type SM‐HTMs (MPA‐BTI and MPA‐BTTI) are devised, which synergistically integrate several design principles for high‐performance HTMs, and exhibit comparable optoelectronic properties but distinct molecular configuration and film properties. Consequently, the dopant‐free MPA‐BTTI‐based inverted PVSCs achieve a remarkable efficiency of 21.17% with negligible hysteresis and superior thermal stability and long‐term stability under illumination, which breaks the long‐time standing bottleneck in the development of dopant‐free SM‐HTMs for highly efficient inverted PVSCs. Such a breakthrough is attributed to the well‐aligned energy levels, appropriate hole mobility, and most importantly, the excellent film morphology of the MPA‐BTTI. The results underscore the effectiveness of the design tactics, providing a new avenue for developing high‐performance dopant‐free SM‐HTMs in PVSCs.

a high conductivity of 0.46 mS cm −1 at room temperature because the three-dimensional pathways in the open framework benefi t the diffusion of Na ions. [ 5 ] Further improvement (60%, 0.74 mS cm −1 ) has been obtained by substitution of Si on P sites in 94Na 3 PS 4 -6Na 4 SiS 4 . [ 6 ] However, the ionic conductivity is still low in comparison to liquid electrolytes, and therefore SEs with higher ionic conductivity need to be sought.Tatsumisago and co-workers found that an appropriate diffusion channel size is critical for fast ion diffusion and anion substitutions have a greater effect on ionic diffusivity than cation substitutions. [ 7 ] Moreover, Se-substituted lithium sulfi des demonstrate an enhanced ionic conductivity in comparison with their pristine compounds. [ 8 ] The advantages of Se-doping lie in two aspects. On one hand, the atomic radius of Se is bigger than that of S, so Se substitution on S sites may expand the lattice. On the other hand, the higher polarizability of Se 2− may weaken the binding energy between the moving ion and the anion framework. These modifi cations may be benefi cial for Na + diffusion because of the big ionic radius of sodium. It is therefore highly interesting to synthesize Na 3 PSe 4 and evaluate its electrochemical performance.In this study, cubic Na 3 PSe 4 was synthesized for the fi rst time and its crystal structure, spectra, and electrochemical performance were investigated. A ionic conductivity of 1.16 mS cm −1 was observed; to the best of our knowledge, this is one of the best values among sodium ion conductors and is the highest value reported for sulfi des to date. Figure 1 a shows the X-Ray Diffraction (XRD) pattern of Na 3 PSe 4 . The halo patterns in both cases refl ect the polyimide fi lm. The crystal structure of Na 3 PSe 4 has not been reported yet. Here, the integrated intensities from powder XRD data were extracted by the Le Bail method using the FullProf program. The crystal structure was solved by using the direct space method and was then refi ned by the Rietveld method. The crystal structure was determined to be cubic with the space group I -43 m (No. 217) and Z = 2. The plots of the observed, calculated, and difference patterns from the Rietveld refi nement (Figure 1 a) evidence the formation of single-phase Na 3 PSe 4 . The refi ned crystallographic data are listed in Table 1 . The cell has a lattice parameter a = 7.3094(2) Å, which is much larger than that of Si-doped Na 3 PS 4 ( a = 6.9978 Å). [ 6 ] A negative isotropic atomic displacement parameter ( U iso ) for P atoms and large U iso values for Na and Se atoms are obtained, indicating large disorders in the crystal structure. Comparison of the XRD patterns of Na 3 PSe 4 before and after ball milling ( Figure S1, Supporting Information) shows that only peak broadening is observed. This observation is in accordance with Differential scanning calorimetry (DSC) results ( Figure S2,The development of large-scale energy-storage system attracts worldwide attention because of the rapidly increasing de...

Chemical doping is a key process for investigating charge transport in organic semiconductors and improving certain (opto)electronic devices 1-9 . N-(electron)doping is fundamentally more challenging than p-(hole)doping and typically achieves very low doping efficiency (η) <10% 1,10 . An efficient molecular n-dopant should simultaneously exhibit a high reducing power and air stability for broad applicability 1,5,6,9,11 , which is very challenging. Here we show a general concept of catalysed n-doping of organic semiconductors using air-stable precursor-type molecular dopants. Incorporation of a transition metal as vapor-deposited nanoparticles (e.g. Pt, Au, Pd) or solution-processable 2 organometallic complexes (e.g. Pd 2 (dba) 3 ) catalyses the reaction, as assessed by experimental and theoretical evidence, enabling drastically increased η in a much shorter doping time and high electrical conductivities >100 S cm −1 12 . This methodology has technological implications for realizing improved semiconductor devices and offers a broad exploration space of ternary systems comprising catalysts, molecular dopants, and semiconductors, thus opening new opportunities in n-doping research and applications.N-doping of organic semiconductors is important for developing light-emitting diodes 1,6-9 , solar cells 7,8 , thin-film transistors 10 , and thermoelectric devices 12,13 . Although solution-based ndoping is widely investigated, only few air-stable n-dopants have been developed (Fig. S1), with the most prominent being organic hydrides 5,9,14-18 such as benzoimidazole derivatives, dimers of organic radicals 11,19,20 such as nineteen-electron organometallic sandwich compounds, and mono-/multi-valent anions 8,21,22 such as OH − , F − and Ox 2− . These air-stable dopants have a deep ionization potential (IP) in their initial forms, thus, cannot directly transfer electrons to n-dope organic semiconductors with a low electron affinity (EA). For anions, it was shown that dispersion into small anhydrous clusters enables sufficiently high donor levels for n-doping organic semiconductors with EAs up to 2.4 eV 8 . Hydride and dimer dopant precursors (or referred as precursor-type dopants) most undergo a C-H and C-C bond cleavage reaction, respectively, to generate active-doping-species in situ before electron transfer can occur [23][24][25][26] . Thus, their reducing strength and reaction kinetics are strongly affected by the thermodynamics and the activation energies of the doping reaction [23][24][25][26] . If the activation energy to the product is reduced, it is expected that the reaction rate, and extent of doping, will greatly increase (Fig. 1a). 3Transition metal (TM) catalysed C-H and C-C bond cleavage reactions are widely used in organic synthesis, with the most common TMs belonging to group 8-11 elements and the catalysts in the form of nanoparticles (NPs) and organometallic complexes 27,28 . Nanoparticle size, supporting material, and chemical structure of the complex can greatly affect catalytic activities. Thus, an i...

Tetragonal Na3SbS4 is synthesized as a new sodium superionic conductor. The discovery of Na vacancies experimentally verifies previous theoretical predictions. Na vacancies, distorted cubic sulphur sublattices and large Na atomic displacement parameters lead to the ionic conductivity as high as 3 mS cm−1, a value significantly higher than those of state‐of‐the‐art sodium sulfide electrolytes.

Unpaired electrons of organic radicals can offer high electrical conductivity without doping, but they typically suffer from low stability. Herein, we report two organic diradicaloids based on quinoidal oligothiophene derivative (QOT), that is, BTICN and QTICN, with high stability and conductivity by employing imide-bridged fused molecular frameworks. The attachment of a strong electron-withdrawing imide group to the tetracyano-capped QOT backbones enables extremely deeply aligned LUMO levels (from −4.58 to −4.69 eV), cross-conjugated diradical characters, and remarkable ambient stabilities of the diradicaloids with half-lives > 60 days, which are among the highest for QOT diradicals and also the widely explored polyaromatic hydrocarbon (PAH)-based diradicals. Specifically, QTICN based on a tetrathiophene imide exhibits a cross-conjugation assisted self-doping in the film state as revealed by XPS and Raman studies. This property in combination with its ordered packing yields a high electrical conductivity of 0.34 S cm −1 for the QTICN films with substantial ambient stability, which is also among the highest values in organic radical-based undoped conductive materials reported to date. When used as an n-type thermoelectric material, QTICN shows a promising power factor of 1.52 uW m −1 K −2 . Our results not only provide new insights into the electron conduction mechanism of the self-doped QOT diradicaloids but also demonstrate the great potential of fused quinoidal oligothiophene imides in developing stable diradicals and high-performance doping-free n-type conductive materials.