Articles you may be interested inSuppression of thermal carrier escape and efficient photo-carrier generation by two-step photon absorption in InAs quantum dot intermediate-band solar cells using a dot-in-well structure J. Appl. Phys. 116, 063510 (2014); 10.1063/1.4892826 Effect of quantum dot position and background doping on the performance of quantum dot enhanced GaAs solar cells Appl. Phys. Lett.High-efficiency InAs/GaAs quantum dot solar cells by metalorganic chemical vapor deposition
All inorganic quantum dot light emitting devices with solution processed
transport layers are investigated. The device consists of an anode, a hole
transport layer, a quantum dot emissive layer, an electron transport layer and a
cathode. Indium tin oxide coated glass slides are used as substrates with the
indium tin oxide acting as the transparent anode electrode. The transport layers
are both inorganic, which are relatively insensitive to moisture and other
environmental factors as compared to their organic counterparts. Nickel oxide
acts as the hole transport layer, while zinc oxide nanocrystals act as the
electron transport layer. The nickel oxide hole transport layer is formed by
annealing a spin coated layer of nickel hydroxide sol-gel. On top of the hole
transport layer, CdSe/ZnS quantum dots synthesized by hot injection method is
spin coated. Finally, zinc oxide nanocrystals, dispersed in methanol, are spin
coated over the quantum dot emissive layer as the electron transport layer. The
material characterization of different layers is performed by using absorbance,
Raman scattering, XRD, and photoluminescence measurements. The completed device
performance is evaluated by measuring the IV characteristics,
electroluminescence and quantum efficiency measurements. The device turn on is
around 4V with a maximum current density of ∼200 mA/cm2 at
9 V.
Anatase and rutile titanium dioxide thin films grown by a low temperature process
are investigated for their use as a single layer antireflection coating for GaAs
solar cells. The thin films are obtained by spin coating a layer from the
TiO2 sol-gel and subsequently annealing at 150 °C. The
sol-gel is synthesized by the hydrolysis of titanium isopropoxide in the
presence of an acid or a base. By controlling the pH of the sol-gel during
growth, pure anatase and rutile phases are obtained. A pH of around 3.0 yields
anatase phase while a pH of 9.0 yields pure rutile phase TiO2. The
two different phases of TiO2 are characterized by measuring the Raman
scattering spectra. The optical constants, thickness and reflectance of the thin
films on GaAs are obtained using a spectroscopic ellipsometer. The sol-gel is
spin coated on GaAs based solar cells and annealed at 150 °C to form
the anti-reflective layer. The performance of the solar cells is evaluated
before and after coating with the TiO2 films. The anatase
TiO2 anti-reflective films performed better than the rutile with a
maximum power conversion efficiency enhancement of 50%. Quantum efficiency
enhancement of 58% and 25% are obtained with anatase and rutile phase films
respectively. The performance enhancement of the solar cells using these thin
films can be attributed to the destructive interference of light associated with
a single layer coating on the solar cell surface.
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