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Papers by Charles Dickson

This document describes photovoltaic research conducted in four areas: semiconductor materials, h... more This document describes photovoltaic research conducted in four areas: semiconductor materials, high-efficiency cells, nonsemiconductor materials, and submodules. The major focus of semiconductor materials research was on improving the quality of wide-band-gap a-SiC:H alloys and narrow-band-gap a-SiGe:H alloys. Raman spectroscopy suggested that the alloys are inhomogeneous, showing a higher concentration of Ge-Ge bonds than expected from a random mixing model. In

Solar Cells, 1987

High performance amorphous silicon solar cells require high quality undoped hydrogenated amorphou... more High performance amorphous silicon solar cells require high quality undoped hydrogenated amorphous silicon (diffusion lengths greater than or equal to 0.5 pm), a conductive p layer or n layer window (Op > 10-6 ~-i cm-1, eopt >~ 2 .0 eV), an effective light trapping geometry such as textured tin oxide, a reflective back contact (e.g. silver) and low contact resistance (less than 0.5 gt cm:). Requirements for high module performance require low interconnect resistance (e.g. less than 5 × 10-a Ft cm: for the A1-SnO2 contact), large percentage of active area and good uniformity of material properties over large areas. New developments such as superlattice doped layers and improved tin oxide texturing have led to efficiencies as high as 10.9% in small cells (1 cm2). Processing improvements have led to efficiencies of 8.1% in 1 ft 2 modules patterned entirely by laser scribing.

Journal of Molecular Spectroscopy, 1975

The chemiluminescence spectrum of atomic Pb reacting with O3 under single-collision conditions in... more The chemiluminescence spectrum of atomic Pb reacting with O3 under single-collision conditions includes a series of 55 bands in the regions 450-850 nm. A vibrational analysis is obtained which shows emission is to the ground state of PbO from excited electronic states not previously analyzed. Forty-nine of the bands are assigned to the a(1)-X(0+) transition and the remaining six are tentatively identified as the forbidden b(0-)-X(0+) transition. Both the a and b states are believed to be Hund's case (c) components of the 3Sigma+ states arising from the configuration sigma2pi3pi*. The vibrational parameters of the a state are nu4 = 16 029 +/- 8, omegae' = 478.7 +/- 1.9, and omegaexe' = 2.292 +/- 0.128 cm-1, where the uncertainties represent two standard deviations of the least-squares fit. Emission is also observed from the PbO B state produced in the reaction of metastable Pb atoms with O3. Using pulsed laser excitation, an attempt is made to determine radiative lifetimes. We find for the PbO A(0+) state tau = 3.74 +/- 0.3 musec, and for the PbO B(1) state tau = 2.58 +/- 0.3 musec, while for the a(1) state tau is estimated to be greater than 10 musec. From the vibrational analysis, energy conservation arguments place a lower limits to the ground state dissociation energy of D00(PbO) >= 3.74 +/- 0.03 eV (86.2 +/- 0.7 kcal/mole). For the Pb + O3 reaction we find less than 1% of the products are PbO* molecules that emit in the visible. Correlations are made with the low-lying states of other Group IV chalconides based on the assignment of the PbO a 3Sigma+(1) state and the correspondence between the low-lying triplet states of PbO and CO.

The Journal of Chemical Physics, 1976

The first known observation of the Dember effect in liquids is reported using a pulsed nitrogen l... more The first known observation of the Dember effect in liquids is reported using a pulsed nitrogen laser (337.1 nm) which generates photocarriers in a solution of anthracene in tetrahydrofuran. From the sign of the Dember signal (diffusion current), the majority photocarriers are determined to be positively charged anthracene ions. The decay of the Dember signal is exponential. This differs from the second-order decay kinetics reported previously in photoconductivity studies of aromatic molecules in solution. The exponential decay is interpreted as a bimolecular recombination process which includes trapping. The relaxation of the photocarriers is significantly altered when the solution is in contact with the electrodes. The Dember signal has a quadratic dependence on the excitation intensity. The photoionization mechanism is shown to result from at least two competing biphotonic absorption mechanisms, the consecutive absorption of two photons and triplet-triplet annihilation.

Described is research on high-efficiency, single-junction, monolithic, thin-film amorphous silico... more Described is research on high-efficiency, single-junction, monolithic, thin-film amorphous silicon solar cells in five task areas: a-Si materials; nonsemiconductor materials; a-Si solar cells; monolithic, intraconnected cells and submodules; and multichamber deposition systems. Researchers found that good film properties can be obtained at a deposition rate of 8 A/s using a 33 percent silane-in-hydrogen mixture; low-level phosphorous-doped a-Si:H films exhibit no detectable degradation with light soaking; and the p-window structure appears to be more stable than the n-window structure. The performance of such top contacts as SnO2/ITO, Ag/ITO, and SnO2/Ag/SnO2 was compared with that of single-layer ITO. A new web treatment system for a-Si solar cells was developed that reduces contamination from the web. Submodules with active areas of more than 70 sqcm were produced with active-area efficiencies of more than 4 percent. The fabrication technique involved laser scribing, screen printing, vapor deposition, and laser heat treatments. A multichamber deposition system was also designed and constructed that deposited a-Si p-i-n and n-i-p layers on a flexible polyimide web in a continuous, roll-to-roll deposition process.

Photovoltaics for Commercial Solar Power Applications, 1986

The Solarex Thin Film Division started commercial production of amorphous silicon solar cells for... more The Solarex Thin Film Division started commercial production of amorphous silicon solar cells for consumer applications in February 1984. Since that time, Solarex has produced more than twenty different types of amorphous silicon solar modules with sizes varying from 0.5cm2 to 1000cm2. The modules contain from 2 to 30 cells connected in series by sequentially patterning the various layers in the solar-cell structure. Conversion efficiencies as high as 10.9% have been obtained with superlattice p layers in 1.16cm2 p-i-n and efficiencies up to 8.7% have been obtained in large area modules (active area = 864cm2).

Journal of the American Chemical Society, 1978

8-0xo-2,2-dimethyl-7~~(l'-hydroxyethyl)-3-oxa-1-azabicyclo[4.2.0]octane (8)6 was converted to its... more 8-0xo-2,2-dimethyl-7~~(l'-hydroxyethyl)-3-oxa-1-azabicyclo[4.2.0]octane (8)6 was converted to its o-nitrobenzylcarbonate 9 (C6H4N02CH202CC1,2 equiv of M~~N C S H~N , 2 equiv of CH2C12,O "Croom temperature, 3 h) and the two isomers a t C-9 were separated by H P L C (silica gel, 30% EtOAc-C6H12). The acetonide function of the 9 R isomer of 9 was hydrolyzed (TFA, H20, room temperature, 12 min) to

Chemical Physics, 1975

We characterize planar diagrams which may be divided into n arc embeddings in terms of their chor... more We characterize planar diagrams which may be divided into n arc embeddings in terms of their chord diagrams, generalizing a result of Taniyama for the case n = 2. Two algorithms are provided, one which finds a minimal arc embedding (in quadradic time in the number of crossings), and one which constructs a minimal subdiagram having same arc number as D.

Applied Physics Letters, 1986

A new device is described for continuous conversion of pure silane into disilane in yields up to ... more A new device is described for continuous conversion of pure silane into disilane in yields up to 40%. The device was used in line with an amorphous silicon deposition system to grow 1-μm-thick films at 300 °C. The minority-carrier diffusion length measured on one of these films was 0.3 μm at one sun illumination. The device can also be used with a synthesis station to collect large quantities of pure disilane. The absence of hydrocarbons, chlorosilanes, and siloxanes at the 10–100 ppm levels was established by analysis of a collected disilane sample.

This document describes photovoltaic research conducted in four areas: semiconductor materials, h... more This document describes photovoltaic research conducted in four areas: semiconductor materials, high-efficiency cells, nonsemiconductor materials, and submodules. The major focus of semiconductor materials research was on improving the quality of wide-band-gap a-SiC:H alloys and narrow-band-gap a-SiGe:H alloys. Raman spectroscopy suggested that the alloys are inhomogeneous, showing a higher concentration of Ge-Ge bonds than expected from a random mixing model. In

Solar Cells, 1987

High performance amorphous silicon solar cells require high quality undoped hydrogenated amorphou... more High performance amorphous silicon solar cells require high quality undoped hydrogenated amorphous silicon (diffusion lengths greater than or equal to 0.5 pm), a conductive p layer or n layer window (Op > 10-6 ~-i cm-1, eopt >~ 2 .0 eV), an effective light trapping geometry such as textured tin oxide, a reflective back contact (e.g. silver) and low contact resistance (less than 0.5 gt cm:). Requirements for high module performance require low interconnect resistance (e.g. less than 5 × 10-a Ft cm: for the A1-SnO2 contact), large percentage of active area and good uniformity of material properties over large areas. New developments such as superlattice doped layers and improved tin oxide texturing have led to efficiencies as high as 10.9% in small cells (1 cm2). Processing improvements have led to efficiencies of 8.1% in 1 ft 2 modules patterned entirely by laser scribing.

Journal of Molecular Spectroscopy, 1975

The chemiluminescence spectrum of atomic Pb reacting with O3 under single-collision conditions in... more The chemiluminescence spectrum of atomic Pb reacting with O3 under single-collision conditions includes a series of 55 bands in the regions 450-850 nm. A vibrational analysis is obtained which shows emission is to the ground state of PbO from excited electronic states not previously analyzed. Forty-nine of the bands are assigned to the a(1)-X(0+) transition and the remaining six are tentatively identified as the forbidden b(0-)-X(0+) transition. Both the a and b states are believed to be Hund's case (c) components of the 3Sigma+ states arising from the configuration sigma2pi3pi*. The vibrational parameters of the a state are nu4 = 16 029 +/- 8, omegae' = 478.7 +/- 1.9, and omegaexe' = 2.292 +/- 0.128 cm-1, where the uncertainties represent two standard deviations of the least-squares fit. Emission is also observed from the PbO B state produced in the reaction of metastable Pb atoms with O3. Using pulsed laser excitation, an attempt is made to determine radiative lifetimes. We find for the PbO A(0+) state tau = 3.74 +/- 0.3 musec, and for the PbO B(1) state tau = 2.58 +/- 0.3 musec, while for the a(1) state tau is estimated to be greater than 10 musec. From the vibrational analysis, energy conservation arguments place a lower limits to the ground state dissociation energy of D00(PbO) >= 3.74 +/- 0.03 eV (86.2 +/- 0.7 kcal/mole). For the Pb + O3 reaction we find less than 1% of the products are PbO* molecules that emit in the visible. Correlations are made with the low-lying states of other Group IV chalconides based on the assignment of the PbO a 3Sigma+(1) state and the correspondence between the low-lying triplet states of PbO and CO.

The Journal of Chemical Physics, 1976

The first known observation of the Dember effect in liquids is reported using a pulsed nitrogen l... more The first known observation of the Dember effect in liquids is reported using a pulsed nitrogen laser (337.1 nm) which generates photocarriers in a solution of anthracene in tetrahydrofuran. From the sign of the Dember signal (diffusion current), the majority photocarriers are determined to be positively charged anthracene ions. The decay of the Dember signal is exponential. This differs from the second-order decay kinetics reported previously in photoconductivity studies of aromatic molecules in solution. The exponential decay is interpreted as a bimolecular recombination process which includes trapping. The relaxation of the photocarriers is significantly altered when the solution is in contact with the electrodes. The Dember signal has a quadratic dependence on the excitation intensity. The photoionization mechanism is shown to result from at least two competing biphotonic absorption mechanisms, the consecutive absorption of two photons and triplet-triplet annihilation.

Described is research on high-efficiency, single-junction, monolithic, thin-film amorphous silico... more Described is research on high-efficiency, single-junction, monolithic, thin-film amorphous silicon solar cells in five task areas: a-Si materials; nonsemiconductor materials; a-Si solar cells; monolithic, intraconnected cells and submodules; and multichamber deposition systems. Researchers found that good film properties can be obtained at a deposition rate of 8 A/s using a 33 percent silane-in-hydrogen mixture; low-level phosphorous-doped a-Si:H films exhibit no detectable degradation with light soaking; and the p-window structure appears to be more stable than the n-window structure. The performance of such top contacts as SnO2/ITO, Ag/ITO, and SnO2/Ag/SnO2 was compared with that of single-layer ITO. A new web treatment system for a-Si solar cells was developed that reduces contamination from the web. Submodules with active areas of more than 70 sqcm were produced with active-area efficiencies of more than 4 percent. The fabrication technique involved laser scribing, screen printing, vapor deposition, and laser heat treatments. A multichamber deposition system was also designed and constructed that deposited a-Si p-i-n and n-i-p layers on a flexible polyimide web in a continuous, roll-to-roll deposition process.

Photovoltaics for Commercial Solar Power Applications, 1986

The Solarex Thin Film Division started commercial production of amorphous silicon solar cells for... more The Solarex Thin Film Division started commercial production of amorphous silicon solar cells for consumer applications in February 1984. Since that time, Solarex has produced more than twenty different types of amorphous silicon solar modules with sizes varying from 0.5cm2 to 1000cm2. The modules contain from 2 to 30 cells connected in series by sequentially patterning the various layers in the solar-cell structure. Conversion efficiencies as high as 10.9% have been obtained with superlattice p layers in 1.16cm2 p-i-n and efficiencies up to 8.7% have been obtained in large area modules (active area = 864cm2).

Journal of the American Chemical Society, 1978

8-0xo-2,2-dimethyl-7~~(l'-hydroxyethyl)-3-oxa-1-azabicyclo[4.2.0]octane (8)6 was converted to its... more 8-0xo-2,2-dimethyl-7~~(l'-hydroxyethyl)-3-oxa-1-azabicyclo[4.2.0]octane (8)6 was converted to its o-nitrobenzylcarbonate 9 (C6H4N02CH202CC1,2 equiv of M~~N C S H~N , 2 equiv of CH2C12,O "Croom temperature, 3 h) and the two isomers a t C-9 were separated by H P L C (silica gel, 30% EtOAc-C6H12). The acetonide function of the 9 R isomer of 9 was hydrolyzed (TFA, H20, room temperature, 12 min) to

Chemical Physics, 1975

We characterize planar diagrams which may be divided into n arc embeddings in terms of their chor... more We characterize planar diagrams which may be divided into n arc embeddings in terms of their chord diagrams, generalizing a result of Taniyama for the case n = 2. Two algorithms are provided, one which finds a minimal arc embedding (in quadradic time in the number of crossings), and one which constructs a minimal subdiagram having same arc number as D.

Applied Physics Letters, 1986

A new device is described for continuous conversion of pure silane into disilane in yields up to ... more A new device is described for continuous conversion of pure silane into disilane in yields up to 40%. The device was used in line with an amorphous silicon deposition system to grow 1-μm-thick films at 300 °C. The minority-carrier diffusion length measured on one of these films was 0.3 μm at one sun illumination. The device can also be used with a synthesis station to collect large quantities of pure disilane. The absence of hydrocarbons, chlorosilanes, and siloxanes at the 10–100 ppm levels was established by analysis of a collected disilane sample.