Admittance Measurements on a-Si/c-Si Heterojunction Solar Cells

Abstract

Hydrogenerated amorphous silicon/crystalline silicon ͑a-Si:H/c-Si͒ solar cells with areas of 1 ϫ 1 cm are produced by deposition of a-Si:H and indium-tin-oxide ͑ITO͒ on 3-in. wafers. Three types of samples have been prepared for admittance measurements, differing in the way how the effective area is defined. The measurement geometry is either defined by cutting, by etching the ITO layer outside the 1 cm 2 active area, or by etching the ITO and the a-Si:H outside the active area. Admittance measurements reveal that the lateral conductivity of the ITO is high enough up to a frequency of 1 MHz to ensure a lateral equipotential surface. A simple equivalent network consisting of a parallel resistor-capacitor branch in series to a second resistor controls the cut sample. For the sample with just ITO layer etching, the effects of a lateral channel due to the a-Si:H layer have to be included. The finite dimensions of the sample modify the low-pass character of the channel. The sample with ITO and a-Si:H layer etching delivers the best measurement conditions. In all three cases the dispersion allows the surface doping level of the substrate to be extracted from the CV characteristics measured at 1 MHz.

III-phosphides heterojunction solar cell interface properties from admittance spectroscopy

“…The influence of the spreading in solar cells on admittance measurements could also be explained in terms of a simplified equivalent circuit [26] where C W (figure 3) should be replaced by the circuit described in figure 12, where C 0 W is the capacitance of the depletion region of the p-n junction placed under the contact grid. The photoactive area (which is not covered by the contact grid) is divided into k parts.…”

An Enhanced Photoelectric Conversion Efficiency of n-Type Crystalline Silicon p—n Junctions Using a Ferroelectric Passivation Layer

“…As a result, whether the light-induced charges (electron-hole pairs) drifted at the top surface of the cell can be collected effectively by Ag gridline electrodes or not, depends on the p-type semiconductor layer, which has a large series resistor (𝑅 s ) due to its poor conductivity. [25] Here light-induced electrons and 047701-2 holes are expelled to the bottom and top of the cell by the built-in field in the p-n junction, respectively. Another factor leading to the poor photovoltaic output of the p-n junction may be attributed to the defects (dangling bonds, etc.)…”

“…When an ITO layer was deposited on the surface of the p-n junction, the series resistor 𝑅 s was reduced due to the fact that the conductivity of ITO (about 15 Ω/cm) was better than that of the p-type silicon layer (about 55 Ω/cm). [25] Furthermore, the oxygen atoms in the ITO layer can diffuse into the surface of the p-type silicon layer and can bind to the dangling bonds. Thus, the recombination centers are reduced greatly.…”