Janis Latvels

A Novel Gas Sensor Transducer Based on Phthalocyanine Heterojunction Devices

Experimental data concerning the changes in the current-voltage (I-V) performances of a molecular material-based heterojunction consisting of hexadecafluorinated nickel phthalocyanine (Ni(F16Pc)) and nickel phthalocyanine (NiPc), (Au|Ni(F16Pc)|NiPc|Al) are introduced as an unprecedented principle of transduction for gas sensing performances. The respective n- and p-type doped-insulator behaviors of the respective materials are supported, owing to the observed changes in surface potential (using the Kelvin probe method) after submission to electron donor (ammonia) and electron acceptor gases (ozone). On the other hand, the bilayer device exhibits strong variations in the built-in potential of the junction and in its rectification ratio. Moreover, large increases occur in forward and reverse currents in presence of ammonia vapors. These make possible a multimodal principle of detection controlled by a combined effect between the heterojunction and the NiPc|Al contact. Indeed, this metal/organic junction plays a critical role regarding the steady asymmetry of the I-V profiles during the devices doping even using high ammonia concentrations. This approach offers a more sophisticated alternative to the classically studied, but at times rather operation-limited, resistive gas sensors.

Photoelectrical properties of thin films of DMABI derivatives

Organic thin films with semiconducting properties have been intensively studied in nowadays due to very promising applications in organic electronics, for example, organic photovoltaic. Among organic semiconductors, group of indandiones with their photoelectrical properties, thermal and chemical stability are good candidates for use in design of novel molecular electronic devices. We have investigated photoconductivity quantum efficiency and its spectral dependence of two dimetilaminobenzylidene-1,3-indandione derivatives. Values of the photoconductivity threshold energy and optical energy gap are obtained. These results are compared with calculated transfer energy gap estimated according to RHF ab initio calculations.

Improvement of Solar PV Efficiency. Potential Materials for Organic Photovoltaic Cells

Abstract Organic photovoltaic (OPV) cells are considered as a viable alternative to those energy sources currently in use. In this work three derivatives of original N,N’- dimetilaminobenziliden-1,3-indandione (DMABI) material are presented as potential materials for OPV. The photoconductivity threshold energy was evaluated from the perspective of spectral dependence of photoconductivity quantum efficiency, and the optical energy gap was defined to determine the optical absorption spectra. The absorption spectra of derivatives are blue shifted compared to original DMABI. Use of these derivatives in multilayer solar cells with original DMABI makes it possible to broaden the spectral response range of OPV.

Photoelectrical properties of indandione fragment containing azobenzene compounds

Organic materials are becoming more popular due to their potential application in electronics. Low molecular weight materials possible produce from solution are in special consideration. It gives the possibility to avoid both thermal evaporation in vacuum, and use of polymers in thin film preparation process. Indandione fragment containing azobenzene compounds are one of such materials. These compounds are good candidates for use in design of novel molecular electronic devices due to their possibility to form amorphous structure from solution thus allowing developing flexible, small size systems with low production costs. In this work three indandione fragment containing azobenzene compounds were investigated. Difference between these compounds is bulky groups which assist formation of amorphous thin film. Absorption spectra of the investigated compounds are similar to P3HT but with higher absorption coefficient. Molecule ionization and electron affinity levels of these compounds are around -5.45eV and -3.80eV, respectively. Combining PCBM with investigated compounds could lead to difference between electron affinity levels maximum of 0.15eV. It is several times less compared to ~1eV for P3HT:PCBM system. Higher difference between the donor ionization level and the acceptor affinity level could also be obtained which should lead to the higher open circuit voltage.