Bulk heterojunction solar cells are fabricated from blends of oligothiophene with a dialkylated diketopyrrolopyrrole chromophore:[6,6]-phenyl C71 butyric acid methyl ester. Absorption and photocurrent of the films extend to 800 nm. A power conversion efficiency (PCE) of 3.0% is obtained under simulated 100 mW/cm2 AM1.5 illumination with a 9.2 mA/cm2 short-circuit current density and an open-circuit voltage of 0.75 V. The hole and electron mobilities in the 50:50 blend are fairly balanced, 1.0×10−4 and 4.8×10−4 cm2/V s, respectively. This is the highest PCE reported to date for solar cells using solution processable small molecules.

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Ambient NO2 adsorption onto copper(II) phthalocyanine (CuPc) monolayers is observed using ultrahigh vacuum (UHV) scanning tunneling microscopy (STM) to elucidate the molecular sensing mechanism in CuPc chemical vapor sensors. For low doses (1 ppm for 5 min) of NO2 at ambient temperatures, isolated chemisorption sites on the CuPc metal centers are observed in STM images. These chemisorbates almost completely desorb from the CuPc monolayer after annealing at 100 °C for 30 min. Conversely, for high NO2 doses (10 ppm for 5 min), the NO2 induces a fracture of the CuPc domains. This domain fracture can only be reversed by annealing above 150 °C, which is consistent with dissociative chemisorption into NO and atomic O accompanied by surface restructuring. This high stability implies that the domain fracture results from tightly bound adsorbates, such as atomic O. Existence of atomic O on or under the CuPc layer, which results in domain fracture, is revealed by XPS analysis and ozone-dosing experiments. The observed CuPc domain fracturing is consistent with a mechanism for the dosimetric sensing of NO2 and other reactive gases by CuPc organic thin film transistors (OTFTs).

The interrelated effects of initial surface preparation and precursor predosing on defect passivation of atomic layer deposited (ALD) Al2O3/InGaAs(100) interfaces are investigated. Interface trap distributions are characterized by capacitance-voltage and conductance-voltage analysis of metal-oxide-semiconductor capacitors. Thermal desorption conditions for a protective As2 layer on the InGaAs surface and dosing conditions of trimethylaluminum prior to ALD-Al2O3 are varied to alter the interface trap densities. Experimental results are consistent with the predictions of ab initio electronic structure calculations showing that trimethylaluminum dosing of the As-rich In0.53Ga0.47As(100) surface suppresses interface traps by passivating As dangling bonds prior to the initiation of Al2O3 deposition.

Articles you may be interested inAtomic imaging of atomic layer deposition oxide nucleation with trimethylaluminum on As-rich InGaAs (001) 2 × 4 vs Ga/In-rich InGaAs(001) 4 × 2 J. Chem. Phys. 136, 154706 (2012); 10.1063/1.4704126Atomic imaging of the monolayer nucleation and unpinning of a compound semiconductor surface during atomic layer deposition Initiation of a passivated interface between hafnium oxide and In ( Ga ) As ( 0 0 1 ) − ( 4 × 2 )Pre-atomic layer deposition surface cleaning and chemical passivation of (100) In 0.2 Ga 0.8 As and deposition of ultrathin Al 2 O 3 gate insulators Using in situ atomic scale imaging with scanning tunneling microscopy/spectroscopy, a combination of atomic hydrogen dosing, annealing, and trimethyl aluminum dosing is observed to produce an ordered unpinned passivation layer on an air exposed InGaAs(001)-(4 Â 2) surface with only monatomic steps. This shows that conventional gate-last semiconductor processing can be employed to fabricate a variety of electronic devices, even on air exposed compound semiconductors.