Amorphous Photodiode with an Intermediate Contact for Improved Color Separation

2011 ◽  
Vol 1305 ◽  
Author(s):  
Krystian Watty ◽  
Andreas Bablich ◽  
Konstantin Seibel ◽  
Christian Merfort ◽  
Markus Boehm
Keyword(s):  
Spectral Sensitivity ◽  
Crystalline Silicon ◽  
Low Cost ◽  
Spectral Response ◽  
High Vacuum ◽  
Color Reproduction ◽  
Device Structure ◽  
External Bias ◽  
Color Separation ◽  
Color Filters

ABSTRACTMost of actual photonic devices being sensitive in the visible (VIS) spectrum are based on crystalline silicon (x-Si). The production of x-Si requires an expensive high temperature process. The color reproduction with x-Si diodes additionally requires an integration of color filters [1] to realize a shift in spectral sensitivity. This work presents an amorphous silicon (a-Si:H) photodiode with an intermediate contact for color separation without color filters. Such detectors can be produced in a low cost and low temperature PECVD process, which allows their direct deposition on a custom specific ASIC [2]. Another advantage of a-Si:H is the up to 10 times higher light absorption compared to that of x-Si in the VIS spectrum [3]. The device consists of a metal (Cr) cathode, an amorphous NIP diode structure and a TCO (Al doped ZnO) anode. The I-layer includes an interior TCO contact buried between two P-layers. The thickness of this TCO layer is about 200 nm; the P-layers have a thickness of about 10 nm. The chromium cathode is sputtered on a glass substrate in a PVD process. The amorphous layers are deposited in a multi-chamber PECVD line; the buried and top TCO contacts are sputtered in the same line continuously under high-vacuum conditions. In a first photolithography step the top anode is patterned while the buried anode is uncovered. Afterwards, the diode must be patterned again, resulting in a final Cr, NIP-a-Si:H, TCO, PIP-a-Si:H and TCO multi-layer stack.The spectral sensitivity of a common NIP diode can be shifted by external bias voltages. The spectral sensitivity at higher negative voltages overlays those of that at lower voltages and additionally shifts to longer wavelengths. The color reproduction is difficult; it can be improved by reducing the overlap of the spectral sensitivity [4]. The spectral response of the diodes presented in this work also can be shifted by the bias voltage. Furthermore, it can be split by substituting the disclosed anodes. The spectral response, using the cathode and top anode has a maximum at short wavelengths. If the diode between the interior anode and the cathode is used, the spectral sensitivity for longer wavelengths increases. Shorter wavelengths are blocked by the top part of the diode; it works like a filter. The presented device structure offers good prospects to improve color separation compared to currently existing detectors by using an additional intermediate contact.

Color separation enhancement of pixn diodes by optimizing absorption regions of a-SiGe:H/a-SiC:H alloys and using a low reflective Al-doped ZnO cathode

2012 ◽  
Vol 1426 ◽  
pp. 181-186 ◽  
Author(s):  
Andreas Bablich ◽  
Krystian Watty ◽  
Christian Merfort ◽  
Markus Boehm
Keyword(s):  
Reverse Bias ◽  
Crystalline Silicon ◽  
Spectral Response ◽  
Reverse Bias Voltage ◽  
Device Structure ◽  
Band Shift ◽  
Response Characteristics ◽  
Interference Fringes ◽  
Back Reflectors ◽  
Graded Layers

ABSTRACTSecurity imaging systems working with crystalline silicon CCD or CMOS detectors are not able to distinguish colorimetrically between a large number of dangerous chemical substances, for example whitish powders [1]. In order to offer an alternative to expensive and destructive chemical methods of analysis, we developed optimized hydrogenated amorphous silicon (a-Si:H) multicolor photodiodes with different spectral response characteristics for a reliable, fast, cheap and non-destructive identification of potentially dangerous substances. Experimental optical, C-V and I-V studies were performed to explore the effect of combining linear graded a‑SiC:H-/a‑SiGe:H layers with low-reflective ZnO:Al back-contacts. Typically, a-Si:H with profiled energy gaps can be found in tandem solar cells to optimize the collection of incoming photons [2,3]. We determined the absorption coefficients of a group of a-SiC:H and a-SiGe:H graded and non-graded layers to calculate the penetration depth of photons at different energies into the device structure. Knowing the indices of absorption, refraction and extinction, it is possible to engineer diodes in such a way that accumulations of charge carriers are generated precisely at varying device depths. Common chromium back reflectors avoid a sharp falling edge of the sensitivity towards longer wavelengths and lead to interference fringes in the spectral response [4]. By combining linear graded absorption zones and ZnO:Al back contacts, we designed an optimized device with a highly precise adjustment of the spectral sensitivity reaching from 420 nm to 560 nm and reduced interference fringes at a very low reverse bias voltage of maximum -2.5 V. Similar three terminal devices allow a shift from 440 nm to 630 nm, however, at a much higher reverse bias of -11 V at 560 nm [4]. Present research efforts concentrate on the development of fast and high dynamic front illumination device structures which ensure a continuous narrow-band shift of the spectral photosensitivity and an optimum adaption to a predetermined light source-/sample measurement configuration.

a-Si:H Photo Diode With Variable Spectral Sensitivity

1996 ◽  
Vol 420 ◽  
Author(s):  
Peter Rieve ◽  
Jürgen Giehl ◽  
Qi Zhu ◽  
Markus Böhm
Keyword(s):  
Thin Film ◽  
Spectral Sensitivity ◽  
Correction Algorithm ◽  
Device Structure ◽  
Band Gap Engineering ◽  
Photo Diode ◽  
Color Separation ◽  
Linearly Independent ◽  
Wide Range ◽  
Color Detection

AbstractA novel two terminal thin film photo diode for color detection has been developed. The device structure which is based on standard amorphous silicon nipin multilayers exhibits three or even more linearly independent spectral sensitivity peaks and provides linearity over a wide range of illumination levels. Band gap engineering and electric field tailoring allow a precise voltage controlled shift of the collection region of photo generated carriers. The steady-state as well as the transient device characteristics have been studied in detail. Emphasis was put on optimization of the spectral sensitivity of the color diodes. Furthermore, an electronic color correction algorithm is presented which results in an improved color separation.

Influence of MBE Growth Conditions on Dislocation Densities of GaAs/Ge Epilayers Grown on Silicon Substrates

1985 ◽  
Vol 43 ◽  
pp. 364-365
Author(s):  
K.M. Hones ◽  
P. Sheldon ◽  
B.G. Yacobi ◽  
A. Mason
Keyword(s):  
High Efficiency ◽  
Lattice Mismatch ◽  
Low Cost ◽  
Growth Conditions ◽  
Nonradiative Recombination ◽  
Device Structure ◽  
Si Substrates ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Dislocation Type

There is increasing interest in growing epitaxial GaAs on Si substrates. Such a device structure would allow low-cost substrates to be used for high-efficiency cascade- junction solar cells. However, high-defect densities may result from the large lattice mismatch (∼4%) between the GaAs epilayer and the silicon substrate. These defects can act as nonradiative recombination centers that can degrade the optical and electrical properties of the epitaxially grown GaAs. For this reason, it is important to optimize epilayer growth conditions in order to minimize resulting dislocation densities. The purpose of this paper is to provide an indication of the quality of the epitaxially grown GaAs layers by using transmission electron microscopy (TEM) to examine dislocation type and density as a function of various growth conditions. In this study an intermediate Ge layer was used to avoid nucleation difficulties observed for GaAs growth directly on Si substrates. GaAs/Ge epilayers were grown by molecular beam epitaxy (MBE) on Si substrates in a manner similar to that described previously.

A novel low cost texturization method for large area commercial mono-crystalline silicon solar cells

2006 ◽  
Vol 90 (20) ◽  
pp. 3557-3567 ◽  
Author(s):  
U. Gangopadhyay ◽  
K.H. Kim ◽  
S.K. Dhungel ◽  
U. Manna ◽  
P.K. Basu ◽  
...  
Keyword(s):  
Solar Cells ◽  
Crystalline Silicon ◽  
Low Cost ◽  
Silicon Solar Cells ◽  
Large Area ◽  
Crystalline Silicon Solar Cells

scholarly journals Preparation of InSe Thin Films by Thermal Evaporation Method and Their Characterization: Structural, Optical, and Thermoelectrical Properties

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Sarita Boolchandani ◽  
Subodh Srivastava ◽  
Y. K. Vijay
Keyword(s):  
Thin Films ◽  
Seebeck Coefficient ◽  
Thermoelectric Power ◽  
Temperature Variation ◽  
Thermal Evaporation ◽  
Low Cost ◽  
High Vacuum ◽  
Power Measurement ◽  
Thermal Evaporation Method ◽  
Evaporation Method

The indium selenium (InSe) bilayer thin films of various thickness ratios, InxSe(1-x) (x = 0.25, 0.50, 0.75), were deposited on a glass substrate keeping overall the same thickness of 2500 Ǻ using thermal evaporation method under high vacuum atmosphere. Electrical, optical, and structural properties of these bilayer thin films have been compared before and after thermal annealing at different temperatures. The structural and morphological characterization was done using XRD and SEM, respectively. The optical bandgap of these thin films has been calculated by Tauc’s relation that varies within the range of 1.99 to 2.05 eV. A simple low-cost thermoelectrical power measurement setup is designed which can measure the Seebeck coefficient “S” in the vacuum with temperature variation. The setup temperature variation is up to 70°C. This setup contains a Peltier device TEC1-12715 which is kept between two copper plates that act as a reference metal. Also, in the present work, the thermoelectric power of indium selenide (InSe) and aluminum selenide (AlSe) bilayer thin films prepared and annealed in the same way is calculated. The thermoelectric power has been measured by estimating the Seebeck coefficient for InSe and AlSe bilayer thin films. It was observed that the Seebeck coefficient is negative for InSe and AlSe thin films.

scholarly journals Индий-индуцированная кристаллизация тонких пленок аморфного субоксида кремния

2020 ◽  
Vol 46 (12) ◽  
pp. 14
Author(s):  
А.О. Замчий ◽  
Е.А. Баранов ◽  
И.Е. Меркулова ◽  
Н.А. Лунев ◽  
В.А. Володин ◽  
...  
Keyword(s):  
Crystallization Temperature ◽  
Polycrystalline Silicon ◽  
Crystalline Silicon ◽  
Solid Phase ◽  
High Vacuum ◽  
Stoichiometric Coefficient ◽  
Free Standing ◽  
Solid Phase Crystallization ◽  
Silicon Suboxide ◽  
Induced Crystallization

A novel fabrication method of polycrystalline silicon by indium-induced crystallization (InIC) of amorphous silicon suboxide thin films with a stoichiometric coefficient of 0.5 (a-SiO0.5) is proposed. It was shown that the use of indium in the annealing process of a SiO0.5 allowed to decrease the crystallization temperature to 600°С which was significantly lower than the solid-phase crystallization temperature of the material - 850°С. As a result of the high-vacuum InIC of a-SiO0.5, the formation of free-standing micron-sized crystalline silicon particles took place.

scholarly journals Investigation of Antireflective Porous Silicon Coating for Solar Cells

2011 ◽  
Vol 2011 ◽  
pp. 1-4 ◽  
Author(s):  
Hyukyong Kwon ◽  
Jaedoo Lee ◽  
Minjeong Kim ◽  
Soohong Lee
Keyword(s):  
Solar Cell ◽  
Porous Silicon ◽  
Crystalline Silicon ◽  
Incident Light ◽  
High Vacuum ◽  
Wavelength Region ◽  
Silicon Layer ◽  
Antireflection Coating ◽  
Reflection Of Light ◽  
Ar Coating

Solar cell is device that directly converts the energy of solar radiation to electrical energy. So it is important for solar cell to reduce the surface reflection of light in order to improve the efficiency of the device. Texturing and antireflection coating have been used to reduce the reflection of light. Texturing technology has reduced the 10% of incident light. However, there are a few disadvantages of random pyramid texturing that the results are not always reproducible in an industrial environment. And AR coating (MgF2, ZnS) is difficult to apply the standard industrial process because high vacuum is needed and the expense is very heavy. This paper investigates the formation of a thin film of porous silicon on the surface of crystalline silicon substrate without other AR coating layers. The formation of the porous silicon layer was measured with SEM (scanning electron microscopy). The formation of porous silicon layers on the textured silicon wafer resulted in lower than 5% of reflectance in the wavelength region from 400 to 1000 nm.

scholarly journals Hybrid Organic-Inorganic Perovskites Open a New Era for Low-Cost, High Efficiency Solar Cells

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Guiming Peng ◽  
Xueqing Xu ◽  
Gang Xu
Keyword(s):  
Solar Cells ◽  
Solar Energy ◽  
High Efficiency ◽  
Low Cost ◽  
Power Conversion ◽  
Perovskite Solar Cells ◽  
Device Structure ◽  
New Era ◽  
High Efficiency Solar Cells ◽  
Conversion Efficiencies

The ramping solar energy to electricity conversion efficiencies of hybrid organic-inorganic perovskite solar cells during the last five years have opened new doors to low-cost solar energy. The record power conversion efficiency has climbed to 19.3% in August 2014 and then jumped to 20.1% in November. In this review, the main achievements for perovskite solar cells categorized from a viewpoint of device structure are overviewed. The challenges and prospects for future development of this field are also briefly presented.

scholarly journals Optical Properties of Spin-Coated TiO2Antireflection Films on Textured Single-Crystalline Silicon Substrates

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Ryosuke Watanabe ◽  
Yohei Eguchi ◽  
Takuya Yamada ◽  
Yoji Saito
Keyword(s):  
Optical Properties ◽  
Crystalline Silicon ◽  
Low Cost ◽  
Incident Light ◽  
Antireflection Coating ◽  
Silicon Wafers ◽  
Reflectance Spectra ◽  
Visible Range ◽  
Single Crystalline Silicon ◽  
Single Crystalline

Antireflection coating (ARC) prepared by a wet process is beneficial for low cost fabrication of photovoltaic cells. In this study, we investigated optical properties and morphologies of spin-coated TiO2ARCs on alkaline textured single-crystalline silicon wafers. Reflectance spectra of the spin-coated ARCs on alkaline textured silicon wafers exhibit no interferences and low reflectance values in the entire visible range. We modeled the structures of the spin-coated films for ray tracing numerical calculation and compared numerically calculated reflectance spectra with the experimental results. This is the first report to clarify the novel optical properties experimentally and theoretically. Optical properties of the spin-coated ARCs without interference are due to the fractional nonuniformity of the thickness of the spin-coated ARCs that cancels out the interference of the incident light.

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