Effects of Grain Boundaries in Amorphous/Multicrystalline Silicon Heterojunction Photovoltaic Cells

2004 ◽  
Vol 836 ◽  
Author(s):  
M. Farrokh Baroughi ◽  
S. Sivoththaman
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Dark Current ◽  
Spectral Response ◽  
Simulation Software ◽  
Multicrystalline Silicon ◽  
Consistent Difference ◽  
Photovoltaic Properties ◽  
Current Voltage ◽  
Current Voltage Characteristics

ABSTRACTSpectral response and dark current-voltage characteristics of heterojunctions are used to investigate grain boundary degradation in photovoltaic properties of a-Si/mc-Si heterojunction solar cells. Measured spectral response inside the grain and on the grain boundary shows small but consistent QE degradation due to minority carrier recombination at the grain boundaries. No consistent difference is observed in dark current-voltage characteristics because of large diode area and periphery leakage current in the employed heterojunction diodes. Comparing measurement results and results from device modeling using the simulation software Medici, a recombination velocity of 4900 cm/sec is found at the grain boundaries of employed multicrystalline silicon wafer. The modeling and experimental results can also be used to define an effective grain area that serves as a measure of grain boundary recombination and the influence of grain size.

Grain Boundary Atomic Structures in SrTiO3 and BaTiO3

2007 ◽  
Vol 558-559 ◽  
pp. 851-856 ◽  
Author(s):  
Takahisa Yamamoto ◽  
Teruyasu Mizoguchi ◽  
S.Y. Choi ◽  
Yukio Sato ◽  
Naoya Shibata ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Annealing Temperature ◽  
Unit Length ◽  
Rate Dependency ◽  
Atomic Structures ◽  
Current Voltage ◽  
Single Grain ◽  
Current Voltage Characteristics ◽  
Theoretical Results

SrTiO3 bicrystals with various types of grain boundaries were prepared by joining two single crystals at high temperature. By using the bicrystals, we examined their current-voltage characteristics across single grain boundaries from a viewpoint of point defect segregation in the vicinity of the grain boundaries. Current-voltage property in SrTiO3 bicrystals was confirmed to show a cooling rate dependency from annealing temperature, indicating that cation vacancies accumulate due to grain boundary oxidation. The theoretical results obtained by ab-initio calculation clearly showed that the formation energy of Sr vacancies is the lowest comparing with Ti and O vacancies in oxidized atomosphere. The formation of a double Schottky barrier (DSB) in n-type SrTiO3 is considered to be closely related to the accumulation of the charged Sr vacancies. Meanwhile, by using three types of low angle boundaries, the excess charges related to one grain boundary dislocation par unit length was estimated. In this study, we summarized our results obtained in our group.

Current-voltage characteristics of ultrafine-grained ferroelectric Pb(Zr, Ti)O3 thin films

1994 ◽  
Vol 9 (6) ◽  
pp. 1484-1498 ◽  
Author(s):  
H. Hu ◽  
S.B. Krupanidhi
Keyword(s):  
Thin Films ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
High Resistivity ◽  
Ultrafine Grained ◽  
Current Voltage ◽  
Electrode Interface ◽  
Current Voltage Characteristics ◽  
Homogeneous Media ◽  
Limited Conduction

Room-temperature current-voltage dependence of ultrafine-grained ferroelectric Pb(Zr, Ti)O3 thin films has been investigated. Both strong varistor type behavior and space charge limited conduction (SCLC) were observed. Differences in the current-voltage characteristics are attributed to differences in the nature of the grain boundaries resulting from variations in processing conditions. The strong varistor type behavior is believed to be due to the presence of highly resistive grain boundaries and thus may be termed grain boundary limited conduction (GBLC). A double-depletion-layer barrier model is used to describe the origin of high resistivity of the grain boundaries. It is suggested that the barrier height varies significantly with the applied field due to the nonlinear ferroelectric polarization, and that the barrier is overcome by tunneling at sufficiently high fields. In some other cases, the resistivity of the grain boundaries is comparable to that of the grains, and therefore the intrinsically heterogeneous films degenerate into quasi-homogeneous media, to which the SCLC theory is applicable. As such, a unified grain boundary modeling reconciles different types of conduction mechanisms in the ultrafine-grained ferroelectric thin films. This grain boundary modeling also well accounts for some other dc-related phenomena observed, including abnormal current-voltage dependencies, remanent polarization effect, electrode interface effect, and unusual charging and discharging transients. In addition, many other electrical properties of the ferroelectric films may be better understood by taking the effect of grain boundaries into account.

Grain boundaries in zinc oxide-based varistor ceramics

1989 ◽  
Vol 47 ◽  
pp. 598-599
Author(s):  
Gun Yong Sung ◽  
Stuart McKernan ◽  
C. Barry Carter
Keyword(s):  
Zinc Oxide ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Breakdown Voltage ◽  
Research Effort ◽  
High Energy ◽  
Zno Varistor ◽  
Current Voltage ◽  
Highly Nonlinear ◽  
Current Voltage Characteristics

Since the development of the zinc oxide-based varistor with highly nonlinear current-voltage characteristics and high energy absorption capabilities [1], the electro-physical behavior of non-ohmic ZnO varistors has been studied and related to the microstructure of the material, the conduction and degradation mechanisms, the dielectric properties, and the high pressure memory. An extensive research effort has been aimed at characterizing ZnO/ZnO grain boundary regions in order to explain the origin of the nonlinear current/voltage characteristics of these materials [2-4]. A typical ZnO-varistor material contains small concentrations of several metal oxides (e.g., Bi2O3, CoO, MnO, Sb2O3, and Cr2O3). Co and Mn are contained within the ZnO grains, while the other “impurities are present as several polymorphic forms of Bi2O3, the spinel, Zn7Sb2O12, and the pyrochlore Zn2Bi3Sb3O14, are present as intergranular phases [1,5-7]. The breakdown voltage depends on the number of grain boundaries between the electrodes of the ZnO varistor device [8]. Therefore, the breakdown voltage is influenced by the presence and form of these intergranular phases, and the size, shape and distribution of the ZnO grains. In ZnO-Bi2O3-MnO-TiO2-based varistor materials, the morphology of the ZnO grains is strongly influenced by their tendency to grow preferentially along the directions perpendicular to the prism planes [9] (i.e., the basal plane becomes a common grain boundary facet plane). The aim of the present study is to advance the understanding of the role of the special grain boundaries which are found in air-quenched Zn0-Bi2O3-MnO-TiO2-based varistor materials.

scholarly journals Understanding Dark Current-Voltage Characteristics in Metal-Halide Perovskite Single Crystals

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Elisabeth A. Duijnstee ◽  
Vincent M. Le Corre ◽  
Michael B. Johnston ◽  
L. Jan Anton Koster ◽  
Jongchul Lim ◽  
...  
Keyword(s):  
Single Crystals ◽  
Dark Current ◽  
Metal Halide ◽  
Metal Halide Perovskite ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
Halide Perovskite

HYBRID NANOMATERIALS FOR MULTI-SPECTRAL INFRARED PHOTODETECTION

2007 ◽  
Vol 17 (01) ◽  
pp. 165-172 ◽  
Author(s):  
ADRIENNE D. STIFF-ROBERTS
Keyword(s):  
Dark Current ◽  
Room Temperature ◽  
Spectral Response ◽  
Substrate Material ◽  
Hybrid Nanomaterials ◽  
Thermally Activated ◽  
Dopant Incorporation ◽  
Quantum Dot Infrared Photodetectors ◽  
Current Voltage ◽  
Fourier Transform Ir

Quantum dot infrared photodetectors (QDIPs) using quantum dots (QDs) grown by strained-layer epitaxy have demonstrated low dark current, multi-spectral response, high operating temperature, and infrared (IR) imaging. However, achieving near room-temperature, multi-spectral operation is a challenge due to randomness in QD properties. The ability to control dopant incorporation is important since charge carrier occupation influences dark current and IR spectral response. In this work, dopant incorporation is investigated in two classes of QDs; epitaxial InAs/GaAs QDs and CdSe colloidal QDs (CQDs) embedded in MEH-PPV conducting polymers. The long-term goal of this work is to combine these hybrid nanomaterials in a single device heterostructure to enable multi-spectral IR photodetection. Two important results towards this goal are discussed. First, by temperature-dependent dark current-voltage and polarization-dependent Fourier transform IR spectroscopy measurements in InAs/GaAs QDIPs featuring different doping schemes, we have provided experimental evidence for the important contribution of thermally-activated, defect-assisted, sequential resonant tunneling. Second, the enhanced quantum confinement and electron localization in the conduction band of CdSe / MEH-PPV nanocomposites enable intraband transitions in the mid-IR at room temperature. Further, by controlling the semiconductor substrate material, doping type, and doping level on which these nanocomposites are deposited, the intraband IR response can be tuned.

Realization of Bulk Multicrystalline Silicon with Controlled Grain Boundaries by Utilizing Spontaneous Modification of Grain Boundary Configuration

2006 ◽  
Vol 45 (3A) ◽  
pp. 1734-1737 ◽  
Author(s):  
Noritaka Usami ◽  
Kentaro Kutsukake ◽  
Takamasa Sugawara ◽  
Kozo Fujiwara ◽  
Wugen Pan ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Multicrystalline Silicon
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