Browsing by Subject "Photovoltaic effects"

Now showing 1 - 5 of 5

Open Access
Chemically specific dynamic characterization of photovoltaic and photoconductivity effects of surface nanostructures
(American Chemical Society, 2010) Ekiz, O. Ö.; Mizrak, K.; Dâna, A.
We report characterization of photovoltaic and photoconductivity effects on nanostructured surfaces through light induced changes in the X-ray photoelectron spectra (XPS). The technique combines the chemical specificity of XPS and the power of surface photovoltage spectroscopy (SPV), with the addition of the ability to characterize photoconductivity under both static and dynamic optical excitation. A theoretical model that quantitatively describes the features of the observed spectra is presented. We demonstrate the applicability of the model on a multitude of sample systems, including homo- and heterojunction solar cells, CdS nanoparticles on metallic or semiconducting substrates, and carbon nanotube films on silicon substrates.
Open Access
Communication: Enhancement of dopant dependent x-ray photoelectron spectroscopy peak shifts of Si by surface photovoltage
(2011) Sezen, H.; Süzer, Şefik
Binding energies measured by x-ray photoelectron spectroscopy (XPS) are influenced by doping, since electrons are transferred to (p-type) and from (n-type) samples when they are introduced into the spectrometer, or brought into contact with each other (p-n junction). We show that the barely measurable Si2p binding energy difference between moderately doped n- and p-Si samples can be enhanced by photoillumination, due to reduction in surface band-bending, which otherwise screens this difference. Similar effects are also measured for samples containing oxide layers, since the band-bending at the buried oxide-Si interfaces is manifest as photovoltage shifts, although XPS does not probe the interface directly. The corresponding shift for the oxide layer of the p-Si is almost twice that of without the oxide, whereas no measurable shifts are observable for the oxide of the n-Si. These results are all related to band-bending effects and are vital in design and performance of photovoltaics and other related systems.
Open Access
Photovoltaic nanocrystal scintillators hybridized on Si solar cells for enhanced conversion efficiency in UV
(Optical Society of American (OSA), 2008) Mutlugun, E.; Soganci I.M.; Demir, Hilmi Volkan
We propose and demonstrate semiconductor nanocrystal based photovoltaic scintillators integrated on solar cells to enhance photovoltaic device parameters including spectral responsivity, open circuit voltage, short circuit current, fill factor, and solar conversion efficiency in the ultraviolet. Hybridizing (CdSe)ZnS core-shell quantum dots of 2.4 nm in diameter on multi-crystalline Si solar cells for the first time, we show that the solar conversion efficiency is enhanced 2 folds under white light illumination similar to the solar spectrum. Such nanocrystal scintillators provide the ability to extend the photovoltaic activity towards UV. © 2008 Optical Society of America.
Open Access
Semiconductor-less photovoltaic device
(IEEE, 2013) Atar, Fatih B.; Battal, Enes; Aygun, Levent E.; Dağlar, Bihter; Bayındır, Mehmet; Okyay, Ali Kemal
We demonstrate a novel semiconductor-less photovoltaic device and investigate the plasmonic effects on this device structure. The device is made of metal and dielectric layers and the operation is based on hot carrier collection. We present the use of surface plasmons to improve energy conversion efficiency. The field localization provided by surface plasmons confine the incident light in the metal layer, increasing the optical absorption and hot electron generation rate inside the metal layer. The device consists of two tandem MIM (metal-insulator-metal) junctions. Bottom MIM junction acts as a rectifying diode and top MIM junction is used to excite surface plasmons. The device operation principle as well as the topology will be discussed in detail. © 2013 IEEE.
Open Access
Triangular metallic gratings for high efficiency thin film solar cells
(IEEE, 2011) Battal, Enes; Yoǧurt, Alper Taha; Aygun, Levent Erdal; Okyay, Ali Kemal
Our design of novel nanometallic structure integrated with photovoltaic devices provides polarization insensitive, broadband and significantly high absorptivity enhancement. This structure attains absorptivities higher than compared to similar thickness of Silicon solar cells with gratings. © 2011 IEEE.