Growth and morphological characterization of intrinsic hydrogenated amorphous silicon thin film for a-Si:H/c-Si heterojunction solar cells

Download
2013
Pehlivan, Özlem
Passivation of the crystalline silicon (c-Si) wafer surface and decreasing the number of interface defects are basic requirements for development of high efficiency a-Si:H/c-Si heterojunction solar cells. Surface passivation is generally achieved by development of detailed silicon wafer cleaning processes and the optimization of PECVD parameters for the deposition of intrinsic hydrogenated amorphous silicon layer. a-Si:H layers are grown in UHV-PECVD system. Solar cells were deposited on the p type Cz-silicon substrates in the structure of Al front contact/a-Si:H(n)/a-Si:H(i)/c-Si(p)/Al back contact. Solar cell parameters were determined under standard test conditions namely, using 1000 W/m2, AM 1.5G illumination at 25 oC. Growth of (i) a-Si:H, films on the clean wafer surface was investigated as a function of substrate temperature, RF power density, gas flow rate, hydrogen dilution ratio and deposition time and was characterized using SEM, HRTEM, AFM, SE, ATR-FTIR and I/V measurements. Structural properties of the films deposited on silicon wafer surface are directly effective on the solar cell efficiency. Morphological characterization of the grown films on the crystalline surface was found to be very complex depending on the deposition parameters and may even change during the deposition time. At 225 oC substrate temperature, at the beginning of the deposition, (i) a-Si:H films was found grown in epitaxial structure, followed by a simultaneous growth of crystalline and amorphous structure, and finally transforming to complete amorphous structure. Despite this complex structure, an efficiency of 9.2% for solar cells with total area of 72 cm2 was achieved. In this cell structure, TCO and back surface passivation do not exist. In the 200 oC temperature region, we realized an existence of process window for the deposition temperature of intrinsic and n-doped layers in our PECVD system. From the post annealing studies, we have observed that solar cell parameters improve when the barrier energy reaches 1.2eV, which is in close agreement with the minimum photon energy for the observation of light induced defects (SWE) in a-Si:H. A model based on breaking of weak Si-Si bonds, bond switching and hydrogen passivation from interface is suggested to explain our results.

Suggestions

Effect of Laser Parameters and Post-Texturing Treatments on the Optical and Electrical Properties of Laser Textured c-Si Wafers
RADFAR, Behrad; ES, FIRAT; NASSER, Hisham; AKDEMİR, Ozan; Bek, Alpan; Turan, Raşit (2018-03-21)
Surface plays a crucial role in the performance of crystalline silicon (cSi) based solar cells as it affects both electrical and optical properties. To minimize reflection from the flat surface and thus improve light trapping, the cSi wafers must be textured. For mono-cSi cells, anisotropic alkaline etchants are commonly utilized to create pyramids on the surface. However, this method is not viable for multi-crystalline silicon (mc-Si) wafers due to the presence of different and random crystallographic orie...
Growth and characterization of branched gold nanoparticles on surfaces
Evcimen, Nimet İlkem; Nalbant Esentürk, Emren; Ünalan, Hüsnü Emrah; Department of Chemistry (2014)
Branched gold nanoparticles, having sharp edges and tips, provide very high sensitivity to local changes in the dielectric environment, as well as large enhancements of the electric field around the nanoparticles. This makes them very attractive for the applications where special optical properties are needed such as sensing, therapeutic treatments and photovoltaic devices. Nanostructures are needed to be stabilized on some type of support for most of these applications.. This can be achieved either by disp...
Efficient Light Trapping in Inverted Nanopyramid Thin Crystalline Silicon Membranes for Solar Cell Applications
MAVROKEFALOS, Anastassios; HAN, Sang Eon; Yerci, Selçuk; Branham, Matthew S.; CHEN, Gang (2012-06-01)
Thin-film crystalline silicon (c-Si) solar cells with light-trapping structures can enhance light absorption within the semiconductor absorber layer and reduce material usage. Here we demonstrate that an inverted nanopyramid light-trapping scheme for c-Si thin films, fabricated at wafer scale via a low-cost wet etching process, significantly enhances absorption within the c-Si layer. A broadband enhancement in absorptance that approaches the Yablo-novitch limit (Yablo-novitch, E. J. Opt. Soc. Am. 1987, 72, ...
Fabrication and doping of thin crystalline Si films prepared by e-beam evaporation on glass substrate
Sedani, Salar Habibpur; Turan, Raşit; Ünalan, Hüsnü Emrah; Department of Micro and Nanotechnology (2013)
In this thesis study, fabrication and doping of silicon thin films prepared by electron beam evaporation equipped with effusion cells for solar cell applications have been investigated. Thin film amorphous Si (a-Si) layers have been fabricated by the electron beam evaporator and simultaneously doped with boron (B) and phosphorous (P) using effusion cells. Samples were prepared on glass substrates for the future solar cell operations. Following the deposition of a-Si thin film, crystallization of the films h...
GROWTH, CHARACTERIZATION AND DEVICE APPLICATIONS OF CADMIUM ZINC TELLURIDE THIN FILMS
Doğru Balbaşı, Çiğdem; Parlak, Mehmet; Department of Physics (2022-5-25)
CdZnTe is an II-VI group semiconductor material with significant properties used in many critical industrial applications, such as photovoltaic devices, photodiodes, photoconductors, room temperature gamma-ray spectroscopy, X-ray imaging, and infrared detectors. In Particular, CdZnTe is a promising material for solar cell application as an absorber layer due to its direct tunable bandgap property, high atomic number with strong absorption, excellent optoelectronic properties, and long-term stability. Howeve...
Citation Formats
Ö. Pehlivan, “Growth and morphological characterization of intrinsic hydrogenated amorphous silicon thin film for a-Si:H/c-Si heterojunction solar cells,” Ph.D. - Doctoral Program, Middle East Technical University, 2013.