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Phosphorus treatment to promote crystallinity of the microcrystalline silicon front contact layers for highly efficient heterojunction solar cells
摘要： The current loss is mainly due to the reflection and the parasitic absorption in the indium tin oxide (ITO) and amorphous silicon (a-Si:H) in the front side of silicon heterojunction (SHJ) solar cells. In this paper, we implemented n-type hydrogenated microcrystalline silicon oxide (n-μc-SiOx:H) as the front surface field (FSF) to improve the short-circuit current density (JSC) of SHJ solar cells. The advantage of employing n-μc-SiOx:H layer is due to its low optical absorption coefficient and tunable refractive index. However, the introduction of carbon dioxide increases light transmission but reduces the crystallinity of n-μc-SiOx:H layer. Meanwhile, inhibiting the incubation layer and increasing microcrystalline/amorphous mixture phase during the growth are critical to the solar cell performance. Therefore, we implemented a high phosphorus-doping seed layer to form a nucleation layer to improve the crystallinity of n-μc-SiOx:H layer. In addition, the plasma enhanced chemical vapor deposition (PECVD) process parameters of each layer were optimized to obtain good optical and electrical properties of n-μc-SiOx:H layer. Finally, a 242.5 cm2 solar cell had been fabricated with conversion efficiency of 23.87%, open-circuit voltage (VOC) of 739.8 mV, fill factor (FF) of 82.33% and JSC of 39.19 mA/cm2, which was 0.31 mA/cm2 higher than that of the conventional n type a-Si:H SHJ solar cells.
关键词： Phosphorus treatment,SHJ solar cells,Crystalline volume fraction,Microcrystalline silicon oxide
更新于2025-09-23 15:19:57
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The effects of air, oxygen and water exposure on the sub-bandgap absorption, the electronic conductivity and the ambipolar diffusion length in highly crystalline microcrystalline silicon films for photovoltaic applications
摘要： Reversible and irreversible changes due to long term air and short term de-ionized water (DIW) or pure oxygen exposure were investigated in about 1 μm thick hydrogenated microcrystalline silicon (μc-Si:H) films deposited on rough glass substrates, thereby comparing highly crystalline with compact material. Time and temperature dependent dark conductivity, steady-state photoconductivity, the steady-state photocarrier grating and dual-beam photoconductivity methods have been used to study the effects. Standard measurement procedures defined previously have been carefully applied to record the changes after different treatments using the steady-state methods under light. After long term air exposure of highly crystalline μc-Si:H films, a thermal annealing step leads to an increase in dark conductivity (σD) and steady-state photoconductivity (σph) as well as to a significant increase in the sub-bandgap absorption. These effects are likely due to a reversible recovery from surface adsorbents in a porous microstructure after air exposure resulting in surface charge and Fermi level shifts in agreement with earlier results. Compact μc-Si:H films showed only marginal effects upon an annealing after long term air exposure suggesting much reduced susceptibility to surface adsorbent induced by Fermi level shifts. Five hours exposure to de-ionized water at 80 °C caused more than an order of magnitude increase in σD and σph and a substantial decrease in the sub-bandgap absorption spectrum in highly crystalline as well as in compact μc-Si:H films. In addition, minority carrier diffusion lengths measured by the steady-state photocarrier grating method improved significantly. The changes after exposure to water were not reversible upon our standard annealing procedure. Exposure to high purity oxygen gas at 150 °C resulted in similar effects like the exposure to DIW. Also here the changes in material properties were not reversible upon annealing. Results are discussed in terms of adsorption and chemical reactions on surfaces in the porous highly crystalline material versus the materials with more compact structures. Results are compared to earlier observations and consequences for device application will be indicated.
关键词： microcrystalline silicon,electronic conductivity,sub-bandgap absorption,photovoltaic applications,ambipolar diffusion length
更新于2025-09-19 17:13:59
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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Zone melting recrystallization of microcrystalline silicon ribbons obtained by chemical vapor deposition
摘要： We present the results achieved with an optical zone melting recrystallization (ZMR) system, which concentrates the radiation of two halogen lamps on the surface of a microcrystalline silicon (μc-Si) ribbon sample, creating a long, 2 mm width molten region (~1414o C). μc-Si ribbon samples measuring up to 25×100 mm2 were previously obtained using an inline optical chemical vapor deposition (CVD) system, that grows silicon layers on top of a silicon dust substrate. Inside the ZMR system, the μc-Si ribbon sample is recrystallized in an argon atmosphere and using a step motor to pull the ribbon at a constant speed between 1 to 6 mm/min, the molten zone travels along the ribbon, recrystallizing the whole sample into a multi-crystalline silicon (mc-Si) ribbon, with an average crystal size in the [1; 10] mm range. It was observed that the physical characteristics of the μc-Si ribbon, like powder substrate incorporation, porosity, thickness, powder grain size used as substrate in the CVD step, have a crucial influence on the recrystallization process and on the electrical properties of the mc-Si ribbon obtained after the ZMR process. Lifetime measurements performed on the recrystallized samples suggest that improvements regarding crystalline quality and possible presence of impurities need to be addressed.
关键词： microcrystalline silicon,solar cells,Zone melting recrystallization,multi-crystalline silicon,chemical vapor deposition
更新于2025-09-12 10:27:22
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P-1.9: Characterization of Self-Aligned Top-Gate Microcrystalline Silicon Thin Film Transistors
摘要： Self-aligned top-gate microcrystalline silicon (μc-Si) thin film transistors (TFTs) are fabricated and characterized. By replacing high-temperature SiO2 with low-temperature SiO2, the performance of self-aligned top-gate μc-Si TFTs can be greatly improved due to the prevention of hydrogen diffusion into the air. The bridged grain (BG) structure is successfully applied to self-aligned top-gate μc-Si TFTs for the first time. By employing the BG doping inside the channel, all device characteristics are improved in self-aligned top-gate μc-Si TFTs.
关键词： Microcrystalline silicon,bridged grain,thin film transistors,self-aligned
更新于2025-09-10 09:29:36
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Effect of deposition rate on the growth mechanism of microcrystalline silicon thin films using very high frequency PECVD
摘要： The intrinsic microcrystalline silicon thin films were deposited by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD). Two series of films with different deposition rate 0.30 nm/s and 1.94 nm/s were prepared. The film surface and gas phase reaction growth processes were monitored with real-time spectroscopic ellipsometry and optical emission spectroscopy. The effect of deposition rate on the microcrystalline silicon thin film growth mechanism has been studied. The microcrystalline silicon surface growth was analyzed with KPZ model. The results show that the growth exponent of β is 0.448 for the films with low deposition rate, and the growth exponent of β is 0.302 for the films with high deposition rate. The growth exponent does not increase with deposition rate, but declines. And the reasons for this phenomenon were explained.
关键词： Real time spectroscopic ellipsometry,Microcrystalline silicon,High rate deposition,Optical emission spectrum,Growth mechanism
更新于2025-09-09 09:28:46
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[IEEE 2018 Iranian Conference on Electrical Engineering (ICEE) - Mashhad (2018.5.8-2018.5.10)] Electrical Engineering (ICEE), Iranian Conference on - Fabrication of P-Type Microcrystalline Silicon Thin Film by Magnetron Sputtering and Copper Induced Crystallization
摘要： P-type micro-crystalline Silicon thin film was realized by magnetron sputtering and copper-induced crystallization for photovoltaic applications. Firstly, amorphous Silicon film was deposited by direct current magnetron sputtering from highly-doped single crystalline Si target. Then it was crystallized by copper-induced crystallization in nitrogen atmosphere with the annealing temperatures ranges from 450 to 950 °C. The micro-crystalline Silicon thin film was characterized by X-ray diffraction and Ramon spectrometry. Its grain size and crystallization ratio were approximately 20 nm and 93%, respectively. Finally, a PN junction solar cell was fabricated by creating the P-type microcrystalline Si thin film (as the P region) on a highly-doped N-type Silicon wafer (as N region). The fabricated device showed the good rectification characteristics of a typical diode where under dark condition it represented the rectification ratio of 150 and reverse saturation current density of 9 μA.cm-2. The fabricated solar cell showed a significant photovoltaic effect under AM 1.5G illumination conditions. The highest photovoltaic conversion efficiency of 2.1%, with the open-circuit voltage of 416 mV and short-circuit current density of 13.3 mA/cm2, was measured from the sample fabricated by the optimal process.
关键词： magnetron sputtering,microcrystalline silicon thin film,copper induced crystallization,characterization
更新于2025-09-09 09:28:46