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The contact interface of heterogeneous organic crystals is used in a wide variety of electronic devices. In recent years, it has become clear that the function of electrical conduction occurs at the heterojunction interface. As a result, the development of new functions at the surface of organic crystals is expected, which requires further investigations. Herein, we assess the charge transfer phenomena and the conductivity at the interface between electron-donor–acceptor crystals. The interface is prepared using (5,10,15,20-tetramethylporphyrinato)cobalt(II) (CoTMP) and 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane (F2TCNQ) as the donor and acceptor crystals, respectively. The surface resistivity of the CoTMP/F2TCNQ interface is extremely low (3 × 105 Ω sq−1), which is one of the lowest values reported thus far for this type of interface. Scanning probe microscopy and electron spin resonance measurements show that 11% of the charge is injected into this interface by contact, and the charge diffusion distance is 200 nm. This distance is significantly higher than the film thickness used in conventional semiconductor devices, thereby indicating that this technique can contribute to the development of organic electronics. [ABSTRACT FROM AUTHOR]

Herein, we introduce a novel effective band tuning method in hybrid tin iodide perovskites using a different group element. With this method, band gap reduction down to 0.8 eV is observed in tin (group 14) iodide-based hybrid perovskites as a result of bismuth (group 15) doping. In this solution-processable material, the band gap is continuously controllable in the range from 1.3 to 0.8 eV even when the doping level was less than 10%. The effect of “foreign metal” doping on the band gap is larger than that of the mixed crystal with the same group elements. Bismuth doping reduces the conductivity of the materials depending on the doping levels though their behavior is still clearly metallic. From the results of the electronic structure and electronic properties of this material, it is clear that bismuth doping causes the narrowing of the band gap without changing the energy and DOS at the top of the valence band, and without increasing the number of carriers. The band tuning method will be useful for the design of solar cells. [ABSTRACT FROM AUTHOR]

An axially ligated Co(tmp) (tmp = 5,10,15,20-tetramethylporphyrinato) anion, [CoIII(tmp)(CN)2]−, has been prepared and subjected to electrochemical oxidation to obtain the open shell tmp π-ligand. With acetone as the solvent, solvent-free neutral radical crystals of CoIII(tmp)(CN)2 are obtained, whereas solvent-inclusive crystals of CoIII(tmp)(CN)2·2CH3CN are obtained with CH3CN as the solvent. In both crystals, the open shell tmp ring deforms into a ruffled form, which makes the π–π interactions in the crystal weak. Thus, the electrical conductivity is low, and the crystals behave as semiconductors with a room temperature resistivity of 106Ω cm and an activation energy of about 0.3 eV. When the solvent is acetone, non-oxidized crystals of the CN-bridged polymer {[CoIII(tmp)(CN)](acetone)}n are obtained as a byproduct. The closed shell tmp ring deforms into a ruffled form, and there π–π interactions in the crystal are negligible. The room temperature resistivity is rather high at about 108Ω cm. [ABSTRACT FROM AUTHOR]

A conducting molecular crystal TPP[MnIII(Pc)(CN)2]2 (MnIII: d4, S = 1, TPP = tetraphenylphosphonium and Pc = phthalocyanine) was fabricated. In its crystal structure, the [MnIII(Pc)(CN)2] units formed a one-dimensional regular chain along the c-axis with an overlap integral value of 8.6 × 10−3. TPP[MnIII(Pc)(CN)2]2 showed a semiconducting behaviour that also has been observed for isostructural TPP[CoIII(Pc)(CN)2]2 (CoIII: d6, S = 0) and TPP[FeIII(Pc)(CN)2]2 (FeIII: d5, S = 1/2) whose ground states are charge-ordered states. In spite of the local magnetic moment of the MnIII ion (S = 1) at the centre of the Pc ligand, TPP[MnIII(Pc)(CN)2]2 exhibited an almost isotropic and small negative magnetoresistance (MR) effect (the MR ratio was −8.7% under 8 T at 10.7 K), contrarily to the anisotropic giant negative MR effect of TPP[FeIII(Pc)(CN)2]2. The isotropy was found to be due to a (dxz)1(dyz)1 electronic configuration, and the smaller MR effect was explained by a weaker antiferromagnetic interaction between MnIII ions than that between FeIII ions, as suggested by a Weiss temperature Θ of −3.1 K (☋Jdd☋/kB = 1.2 K). [ABSTRACT FROM AUTHOR]

Electrical properties of solution-grown organic–inorganic hybrid tin bromide perovskite crystals were evaluated. The resistivity of the as-grown crystal is 106–1010Ω cm though hole doping of Sn(iv) results in a resistivity decrease by 1–5 orders of magnitude. The activation energy of the semiconducting regime was lower than the one expected on the basis of the band gap. This result suggests that the spontaneous doping as observed for the tin iodide system also occurs for tin bromide, although in this case the acceptor level is separated from the top of the valence band. Iodide substitution effects in tin bromide crystal were investigated using CH3NH3SnBr3(1−x)I3x (0 ≤x≤ 1) crystals with variable bromide/iodide ratio. The room temperature resistivity monotonously decreases with increasing iodide content, x. The behavior and optical properties can be explained by the band model in which iodide substitution lifts up the top of the valence band and makes the energy difference to the acceptor levels smaller. In addition, a negative differential resistance behavior was observed in the bromide-rich region. [ABSTRACT FROM AUTHOR]

An axially ligated Co(tmp) (tmp = 5,10,15,20-tetramethylporphyrinato) anion, [CoIII(tmp)(CN)2]−, has been prepared and subjected to electrochemical oxidation to obtain the open shell tmp π-ligand. With acetone as the solvent, solvent-free neutral radical crystals of CoIII(tmp)(CN)2 are obtained, whereas solvent-inclusive crystals of CoIII(tmp)(CN)2·2CH3CN are obtained with CH3CN as the solvent. In both crystals, the open shell tmp ring deforms into a ruffled form, which makes the π–π interactions in the crystal weak. Thus, the electrical conductivity is low, and the crystals behave as semiconductors with a room temperature resistivity of 106Ω cm and an activation energy of about 0.3 eV. When the solvent is acetone, non-oxidized crystals of the CN-bridged polymer {[CoIII(tmp)(CN)](acetone)}n are obtained as a byproduct. The closed shell tmp ring deforms into a ruffled form, and there π–π interactions in the crystal are negligible. The room temperature resistivity is rather high at about 108Ω cm. [ABSTRACT FROM AUTHOR]

An axially ligated Co(tmp) (tmp = 5,10,15,20-tetramethylporphyrinato) anion, [Co III (tmp)(CN) 2 ] - , has been prepared and subjected to electrochemical oxidation to obtain the open shell tmp π-ligand. With acetone as the solvent, solvent-free neutral radical crystals of Co III (tmp)(CN) 2 are obtained, whereas solvent-inclusive crystals of Co III (tmp)(CN) 2 ·2CH 3 CN are obtained with CH 3 CN as the solvent. In both crystals, the open shell tmp ring deforms into a ruffled form, which makes the π-π interactions in the crystal weak. Thus, the electrical conductivity is low, and the crystals behave as semiconductors with a room temperature resistivity of 10 6 Ω cm and an activation energy of about 0.3 eV. When the solvent is acetone, non-oxidized crystals of the CN-bridged polymer {[Co III (tmp)(CN)](acetone)} n are obtained as a byproduct. The closed shell tmp ring deforms into a ruffled form, and there π-π interactions in the crystal are negligible. The room temperature resistivity is rather high at about 10 8 Ω cm.

A conducting molecular crystal TPP[Mn III (Pc)(CN) 2 ] 2 (Mn III : d 4 , S = 1, TPP = tetraphenylphosphonium and Pc = phthalocyanine) was fabricated. In its crystal structure, the [Mn III (Pc)(CN) 2 ] units formed a one-dimensional regular chain along the c-axis with an overlap integral value of 8.6 × 10 -3 . TPP[Mn III (Pc)(CN) 2 ] 2 showed a semiconducting behaviour that also has been observed for isostructural TPP[Co III (Pc)(CN) 2 ] 2 (Co III : d 6 , S = 0) and TPP[Fe III (Pc)(CN) 2 ] 2 (Fe III : d 5 , S = 1/2) whose ground states are charge-ordered states. In spite of the local magnetic moment of the Mn III ion (S = 1) at the centre of the Pc ligand, TPP[Mn III (Pc)(CN) 2 ] 2 exhibited an almost isotropic and small negative magnetoresistance (MR) effect (the MR ratio was -8.7% under 8 T at 10.7 K), contrarily to the anisotropic giant negative MR effect of TPP[Fe III (Pc)(CN) 2 ] 2 . The isotropy was found to be due to a (d xz ) 1 (d yz ) 1 electronic configuration, and the smaller MR effect was explained by a weaker antiferromagnetic interaction between Mn III ions than that between Fe III ions, as suggested by a Weiss temperature Θ of -3.1 K (|J dd |/k B = 1.2 K).

The partially-oxidized TPP[M(Pc)L(2)](2) molecular conductors exhibit variable electronic and magnetic transport bulk materials properties due to central metal and axial ligand molecular modifications. The controllable electrical conductivity and giant negative magnetoresistance can be mainly attributable to the varying ligand field energy and physical bulkiness of the axial ligands which cause modulation in the intra-molecular π-d (Pc-M) and inter-molecular π-π (Pc-Pc) interactions in the TPP[M(Pc)L(2)](2) system, respectively. Characterization of the electronic conduction band utilizing one-dimensional (1-D) tight-binding approximation from infrared reflectance and thermoelectric power profile reveal consistent band widths of 0.43 eV-0.62 eV for the Co series (L = Br < Cl < CN) and 0.44-0.56 eV for the Fe series (L = Br < Cl < CN). The fixed band width suggests that stable electron conduction bands (transport pathway) can be constructed which can withstand the molecular π-d interaction modifications that severely alter the bulk electronic and magnetic materials properties of the TPP[M(Pc)L(2)](2) molecular conductors.