Mixed Ionic and Electronic Conduction in Li_3PO_4 Electrolyte for a CO_2 Gas Sensor

An electrochemical CO_2 gas sensor using Li_2CO_3 and Li_2TiO_3+TiO_2 as sensing and reference electrodes, respectively, and Li_3PO_4 as the electrolyte is the subject of this paper. The sensor response to CO_2 gas showed a systematic deviation from the prediction of the Nernst equation at low pCO_2. Based on the electromotive force (emf) measurement, the transference numbers of Li_3PO_4, a lithium-ion conductor, were estimated for different pCO_2 values, and the conduction domain boundary for Li_3PO_4 separating n-type electronic conduction from ionic conduction was constructed. The conduction domain predicts that change in the Li activity in the sensing side of the cell drives the Li_3PO_4 electrolyte to a mixed (n-type electronic and ionic) conduction region at low pCO_2. Hebb-Wagner dc polarization measurements also indicate n-type electronic conduction in Li_3PO_4 with a mixture of Li_2CO_3 and gold as a reversible electrode. The transference numbers obtained from both the emf measurement and the Hebb-Wagner polarization measurements demonstrate that the origin of the non-Nernstian behavior of the CO_2 sensor is due to the lithium mass transport from the Li_2CO_3-sensing electrode to the Li_3PO_4 electrolyte, resulting in nonstoichiometry of Li_3PO_4 at temperatures above 500°C

Impedance Spectroscopic Study of p-i-n Type a-Si Solar Cell by Doping Variation of p-Type Layer

We investigated p-i-n type amorphous silicon (a-Si) solar cell where the diborane flow rate of the p-type layer was varied and the solar cell was measured static/dynamic characteristics. The p/i interface of the thin film amorphous silicon solar cells was studied in terms of the coordination number of boron atoms in the p layer. p-type layer and p/i interface properties were obtained from the X-ray photoelectron spectroscopy (XPS) and impedance spectroscopy. One of the solar cells shows open circuit voltage (oc)=880 mV, short circuit current density (sc)=14.21 mA/cm2, fill factor (FF)=72.03%, and efficiency ()=8.8% while the p-type layer was doped with 0.1%. The impedance spectroscopic measurement showed that the diode ideality factor and built-in potential changed with change in diborane flow rate

Triple-Junction Hybrid Tandem Solar Cells with Amorphous Silicon and Polymer-Fullerene Blends

Organic-inorganic hybrid tandem solar cells attract a considerable amount of attention due to their potential for realizing high efficiency photovoltaic devices at a low cost. Here, highly efficient triple-junction (TJ) hybrid tandem solar cells consisting of a double-junction (DJ) amorphous silicon (a-Si) cell and an organic photovoltaic (OPV) rear cell were developed. In order to design the TJ device in a logical manner, a simulation was carried out based on optical absorption and internal quantum efficiency. In the TJ architecture, the high-energy photons were utilized in a more efficient way than in the previously reported a-Si/OPV DJ devices, leading to a significant improvement in the overall efficiency by means of a voltage gain. The interface engineering such as tin-doped In2O3 deposition as an interlayer and its UV-ozone treatment resulted in the further improvement in the performance of the TJ solar cells. As a result, a power conversion efficiency of 7.81% was achieved with an open-circuit voltage of 2.35 V. The wavelength-resolved absorption profile provides deeper insight into the detailed optical response of the TJ hybrid solar cells