Photocarrier Transport and Recombination in Amorphous Silicon

1993 ◽  
Vol 297 ◽  
Author(s):  
C.R. Wronski ◽  
R.M. Dawson ◽  
M. Gunes ◽  
Y.M. Li ◽  
R.W. Collins
Keyword(s):  
Solar Cell ◽  
Carrier Mobility ◽  
Carrier Transport ◽  
Room Temperature ◽  
Dark Conductivity ◽  
Conductivity Measurements ◽  
Dangling Bond ◽  
Dual Beam ◽  
Temperature Electron ◽  
Gap States

The effect of microstructure in undoped a-Si:H films on carrier transport, recombination, densities of midgap states and solar cell characteristics has been investigated. Extended state mobilities of electrons were obtained from photo and dark conductivity measurements between 40° C and 190° C and the gap states characterized using Dual Beam Photoconductivity. In these films the estimated room temperature electron mobilities increase from about 1 to 30 cm2/V sec as the dihydride concentrations and void volume fractions decrease. It is found that the carrier mobility-lifetime products are not solely determined by the dangling bond states. The effects of changes in the mobilities and midgap states on p-i-n homojunction solar cell characteristics are presented and discussed.

Temperature Dependent Line-Shape of the Silicon Dangling Bond EPR-Resonance in Polycrystalline Silicon

1996 ◽  
Vol 452 ◽  
Author(s):  
N. H. Nickel ◽  
E. A. Schiff
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Polycrystalline Silicon ◽  
Room Temperature ◽  
Dangling Bond ◽  
Temperature Dependent ◽  
Paramagnetic Resonance ◽  
Temperature Electron ◽  
Motional Narrowing ◽  
G Value ◽  
Electron Paramagnetic

AbstractThe temperature dependence of the silicon dangling-bond resonance in polycrystalline (poly-Si) and amorphous silicon (a-Si:H) was measured. At room temperature, electron paramagnetic resonance (EPR) measurements reveal an isotropie g-value of 2.0055 and a line width of 6.5 and 6.1 G for Si dangling-bonds in a-Si:H and poly-Si, respectively. In both materials spin density and g-value are independent of temperature. While in a-Si:H the width of the resonance did not change with temperature, poly-Si exhibits a remarkable T dependence of ΔHpp. In unpassivated poly-Si a pronounced decrease of ΔHpp is observed for temperatures above 300 K. At 384 K ΔHpp reaches a minimum of 5.1 G, then increases to 6.1 G at 460 K, and eventually decreases to 4.6 G at 530 K. In hydrogenated poly-Si ΔHpp decreases monotonically above 425 K. The decrease of ΔHpp is attributed to electron hopping causing motional narrowing. An average hopping distance of 15 and 17.5 Å was estimated for unhydrogenated and H passivated poly-Si, respectively.

Field Effect Mobility of F16PcCu Films in Various Gas Atmospheres

1999 ◽  
Vol 03 (07) ◽  
pp. 667-671 ◽  
Author(s):  
HIROKAZU TADA ◽  
HIROSHI TOUDA ◽  
MASAKI TAKADA ◽  
KAZUMI MATSUSHIGE
Keyword(s):  
Carrier Density ◽  
Field Effect ◽  
Carrier Mobility ◽  
Carrier Transport ◽  
Room Temperature ◽  
Gas Adsorption ◽  
Quick Recovery ◽  
Thermally Activated ◽  
High Carrier ◽  
Gas Molecules

The electron mobility of hexadecafluorophthalocyaninato-copper ( F 16 PcCu ) films was evaluated based on field effect measurements in vacuum and in various gas atmospheres. An Arrhenius plot of the mobility showed that the carrier transport followed a thermally activated hopping mechanism with an activation energy of 0.28 eV. The mobility evaluated for freshly prepared films in ultrahigh vacuum was 2.0 × 10−3 cm 2 V −1 s −1 at room temperature. The electrical conductivity and carrier density were 4.4 × 10−5 S cm −1 and 1.4 × 1017 cm −3 respectively. The high carrier density indicated the existence of impurities acting as electron donors in the films. The field effect carrier mobility increased to 5.7 × 10−3 cm 2 V −1 s −1 in NH 3 atmosphere (100%, 1 atm) and decreased by 75% in the presence of O 2 gas (100%, 1 atm). A quick recovery of mobility was observed when the gas molecules were evacuated, indicating a low capability of gas adsorption.

ON THE ANOMALOUS STEADY-STATE DARK CONDUCTIVITY INa-SeFILMS

2009 ◽  
Vol 23 (26) ◽  
pp. 5171-5177 ◽  
Author(s):  
N. QAMHIEH ◽  
I. M. OBAIDAT ◽  
F. HAMED
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Thermal Evaporation ◽  
Dark Conductivity ◽  
Amorphous Selenium ◽  
Conductivity Measurements ◽  
Thermally Activated ◽  
Current Voltage ◽  
Chalcogenide Semiconductors ◽  
Dark Currents

Thin films of amorphous selenium ( a-Se ) have been prepared by thermal evaporation. DC conductivity measurements were carried out on these films in the temperature range between 60 and -50° C . Above room temperature, the dark conductivity is thermally activated as usually observed in chalcogenide semiconductors. At low temperatures, the unexpected increase in the dark currents could be attributed to the phase change in the a-Se film. The current–voltage, I–V, curves showed a phase transition temperature of about 10°C.

scholarly journals Structure and Doping Optimization of IDT-Based Copolymers for Thermoelectrics

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1463
Author(s):  
Tongchao Liu ◽  
Dexun Xie ◽  
Jinjia Xu ◽  
Chengjun Pan
Keyword(s):  
Organic Semiconductors ◽  
Carrier Mobility ◽  
Carrier Transport ◽  
Room Temperature ◽  
Charge Carrier Transport ◽  
Structure Property ◽  
Polymer Backbone ◽  
Donor Acceptor ◽  
Higher Carrier Mobility ◽  
The Relationship

π-conjugated backbones play a fundamental role in determining the thermoelectric (TE) properties of organic semiconductors. Understanding the relationship between the structure–property–function can help us screen valuable materials. In this study, we designed and synthesized a series of conjugated copolymers (P1, P2, and P3) based on an indacenodithiophene (IDT) building block. A copolymer (P3) with an alternating donor–acceptor (D-A) structure exhibits a narrower band gap and higher carrier mobility, which may be due to the D-A structure that helps reduce the charge carrier transport obstacles. In the end, its power factor reaches 4.91 μW m−1 K−2 at room temperature after doping, which is superior to those of non-D-A IDT-based copolymers (P1 and P2). These results indicate that moderate adjustment of the polymer backbone is an effective way to improve the TE properties of copolymers.

Optical and electronic properties of amorphous SiNx:H alloy films

1985 ◽  
Vol 63 (6) ◽  
pp. 846-851 ◽  
Author(s):  
T. V. Herak ◽  
R. D. McLeod ◽  
M. G. Collett ◽  
K. C. Kao ◽  
H. C. Card ◽  
...  
Keyword(s):  
Nitrogen Content ◽  
Electronic Properties ◽  
Optical Excitation ◽  
Dark Conductivity ◽  
Dangling Bond ◽  
Alloy Films ◽  
Optical And Electronic Properties ◽  
Rf Glow Discharge ◽  
Gap States ◽  
Induced Changes

The optical and electronic properties of a-SiNx:H alloy films fabricated by rf glow discharge have been measured for 0 ≤ x ≤ 0.6. The material is dispersive over the range of photon energies 0.5 ≤ hv ≤ 3.5 eV. The optical gap is about 1.65 eV and is practically independent of x for 0.1 < x < 0.4, but it increases rapidly with increasing x for 0 < x < 0.1 and x > 0.4. For x > 0.6 the refractive index approaches the value for Si3N4. The dark conductivity, the photoconductivity, and the ratio of the photoconductivity to the dark conductivity are enhanced by nitrogen incorporation when appropriate nitrogen content is used. All the experimental results indicate that the incorporated nitrogen does not act as a dopant, but rather acts as a dangling-bond compensator. Photo-induced changes in both dark conductivity and photoconductivity due to high-intensity optical excitation have been observed. The degree of such changes decreases with increasing nitrogen content. This phenomenon is attributed to the photo-induced change in the microstructure of the films that leads to a change in both the density and the distribution of gap states.

Steady State Photocarrier Charge Collection in a-Si:H for Electrons and Holes

1991 ◽  
Vol 219 ◽  
Author(s):  
C.-D. Abel ◽  
H. R. Paes ◽  
G. H. Bauer
Keyword(s):  
Steady State ◽  
Amorphous Silicon ◽  
Carrier Transport ◽  
Room Temperature ◽  
Charge Collection ◽  
Electron Charge ◽  
Extended State ◽  
Pin Diodes ◽  
Temperature Electron ◽  
Generation Region

AbstractCarrier transport in amorphous silicon pin-diodes has been analyzed by steady state photocarrier charge collection applying strongly absorbed light. For low intensities at room temperature electron charge collection is limited by recombination in the generation region. For increasing intensity ø and/or decreasing temperature charge collection becomes nonlinear in ø and shows S-like characteristics versus voltage.We present a model for this behaviour, including space charge limitation which e.g. for holes in a-Si:H limits charge collection even at room temperature due to low extended state mobility of holes and dark Fermi level position above midgap.

Absorption and photoluminescence studies of lightly alloyed CdTe(S) and CdS(Te)

2001 ◽  
Vol 668 ◽  
Author(s):  
Diana Shvydka ◽  
A.D. Compaan ◽  
K.J. Price
Keyword(s):  
Solar Cell ◽  
Band Gap ◽  
Room Temperature ◽  
Rf Sputtering ◽  
Near Band Edge ◽  
Photoluminescence Excitation ◽  
Defect States ◽  
Rich Alloy ◽  
Photoluminescence Studies ◽  
Gap States

ABSTRACTCdTe-rich and CdS-rich alloy films were deposited at temperatures less than 300C using an rf sputtering technique. Transmission-reflection and photoluminescence measurements were conducted to study the near-band edge properties of this ternary system for films of different compositions at room temperature and at 10K. Results were compared to data on defect states introduced in CdTe single crystal by annealing at several different overpressure conditions, including CdS and CdCl2 overpressures. A below-band-gap photoluminescence excitation technique was used to study systematically the effect of different steps in the production of the complete solar cell on band gap states of CdSxTe1−x alloys as well as pure binary constituents.

scholarly journals Universal mobility characteristics of graphene originating from charge scattering by ionised impurities

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jonathan H. Gosling ◽  
Oleg Makarovsky ◽  
Feiran Wang ◽  
Nathan D. Cottam ◽  
Mark T. Greenaway ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Carrier Density ◽  
Carrier Mobility ◽  
Carrier Transport ◽  
Analytical Models ◽  
Pristine Graphene ◽  
High Electron ◽  
Boltzmann Transport ◽  
Transport Parameters ◽  
Wide Range

AbstractPristine graphene and graphene-based heterostructures can exhibit exceptionally high electron mobility if their surface contains few electron-scattering impurities. Mobility directly influences electrical conductivity and its dependence on the carrier density. But linking these key transport parameters remains a challenging task for both theorists and experimentalists. Here, we report numerical and analytical models of carrier transport in graphene, which reveal a universal connection between graphene’s carrier mobility and the variation of its electrical conductivity with carrier density. Our model of graphene conductivity is based on a convolution of carrier density and its uncertainty, which is verified by numerical solution of the Boltzmann transport equation including the effects of charged impurity scattering and optical phonons on the carrier mobility. This model reproduces, explains, and unifies experimental mobility and conductivity data from a wide range of samples and provides a way to predict a priori all key transport parameters of graphene devices. Our results open a route for controlling the transport properties of graphene by doping and for engineering the properties of 2D materials and heterostructures.

Structure and Conductivity of Iodine-Doped C60 Thin Films

1994 ◽  
Vol 359 ◽  
Author(s):  
Jun Chen ◽  
Haiyan Zhang ◽  
Baoqiong Chen ◽  
Shaoqi Peng ◽  
Ning Ke ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Room Temperature ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
X Ray ◽  
Thermally Activated ◽  
Order Of Magnitude

ABSTRACTWe report here the results of our study on the properties of iodine-doped C60 thin films by IR and optical absorption, X-ray diffraction, and electrical conductivity measurements. The results show that there is no apparent structural change in the iodine-doped samples at room temperature in comparison with that of the undoped films. However, in the electrical conductivity measurements, an increase of more that one order of magnitude in the room temperature conductivity has been observed in the iodine-doped samples. In addition, while the conductivity of the undoped films shows thermally activated temperature dependence, the conductivity of the iodine-doped films was found to be constant over a fairly wide temperature range (from 20°C to 70°C) exhibiting a metallic feature.

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