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

Download

index.pdf

Date

2013

Author

Pehlivan, Özlem

Metadata

Show full item record

Item Usage Stats

243
views

153
downloads

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.

Subject Keywords

Silicon., Crystals., Thin films., Solar cells., Amorphous silicon.

URI

http://etd.lib.metu.edu.tr/upload/12615488/index.pdf
https://hdl.handle.net/11511/22269

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Contact resistivity analysis of different passivation layers via transmission line method measurements Kökbudak, Gamze; Turan, Raşit; Yerci, Selçuk; Department of Micro and Nanotechnology (2017) Crystalline silicon (c-Si) homojunction solar cells constitute over 90% of the current photovoltaic market. Although the standard solar cells are cost effective and easy to process, their efficiency potential is unfortunately limited. Currently, more innovative cell concepts appeared with their high efficiency potential coupled with low costs. Since the recombination at surfaces and under metal contacts is one of the major obstacles against high conversion efficiencies, surface passivation has primary impor...
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...
Development of hole transport transparent conductive electrodes for n-type crystalline silicon solar cells Akdemir, Ozan; Bek, Alpan; İmer, Muhsine Bilge; Department of Micro and Nanotechnology (2018) Conventional transparent conductive electrodes (TCEs) used in crystal silicon (c-Si) solar cells are commonly made of indium tin oxide (ITO) which provides low sheet resistance and high transparency. However, due to indium scarcity, ITO layers increase the fabrication cost; thus, alternative TCEs, such as fluorine-doped tin oxide (FTO), zinc oxide (ZnO), metal nanowires and Oxide/Metal/Oxide (OMO) multilayers, are being investigated. Conventional solar cells also make use of doped layers, to create the junc...
Surface modification of multi-crystalline silicon in photovoltaic cell by laser texturing Radfar, Behrad; Turan, Raşit; Yerci, Selçuk; Department of Micro and Nanotechnology (2019) Surface of crystalline silicon solar cell plays an important role in its performance. It affects the optical properties which can be determined by surface’ reflectance. To minimize the reflection from the flat surface, thus, improve light trapping, the crystalline silicon wafers must be textured. Through the texturing process, roughness is introduced at the surface, so the incident light has a larger probability of being absorbed into the solar cell. Monocrystalline silicon solar cells can typically be text...
Fabrication of thin crystalline silicon solar cells with advanced light trapping Hadibrata, Wisnu; Yerci, Selçuk; Turan, Raşit; Department of Micro and Nanotechnology (2017) Thin crystalline silicon (c-Si) solar cells with thickness in the order of few tens of microns offer many attractive applications, such as, electronic wearables, space probes and satellites thanks to their flexibility and light-weight character. However, reducing the thickness of active layer of silicon solar cells leads to poor light absorption within the silicon layer, especially in the near infrared region of the solar spectrum. The poor absorption becomes problematic for thin c-Si solar cells as it caus...

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.