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Screen printing process control for coating high throughput titanium dioxide films toward printable mesoscopic perovskite solar cells
Zhining WAN, Mi XU, Zhengyang FU, Da LI, Anyi MEI, Yue HU, Yaoguang RONG, Hongwei HAN
Front. Optoelectron.. 2019, 12 (4 ): 344-351.
https://doi.org/10.1007/s12200-019-0904-7
Screen printing technique has been widely applied for the manufacturing of both traditional silicon solar cells and emerging photovoltaics such as dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs). Particularly, we have developed a printable mesoscopic PSC based on a triple layer scaffold of TiO2 /ZrO2 /carbon. The deposition of the scaffold is entirely based on screen printing process, which provides a promising prospect for low-cost photovoltaics. However, the optimal thickness of the TiO2 layer for fabricating efficient printable PSCs is much smaller than the typical thickness of screen printed films. Here, we tune the concentration of the pastes and the printing parameters for coating TiO2 films, and successfully print TiO2 films with the thickness of 500−550 nm. The correlation between the thickness of the films and printing parameters such as the solid content and viscosity of the pastes, the printing speed and pressure, and the temperature has been investigated. Besides, the edge effect that the edge of the TiO2 films possesses a much larger thickness and printing positional accuracy have been studied. This work will significantly benefit the further development of printable mesoscopic PSCs.
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Antimony doped Cs2 SnCl6 with bright and stable emission
Jinghui LI, Zhifang TAN, Manchen HU, Chao CHEN, Jiajun LUO, Shunran LI, Liang GAO, Zewen XIAO, Guangda NIU, Jiang TANG
Front. Optoelectron.. 2019, 12 (4 ): 352-364.
https://doi.org/10.1007/s12200-019-0907-4
Lead halide perovskites, with high photoluminescence efficiency and narrow-band emission, are promising materials for display and lighting. However, the lead toxicity and environmental sensitivity hinder their potential applications. Herein, a new antimony-doped lead-free inorganic perovskites variant Cs2 SnCl6 :x Sb is designed and synthesized. The perovskite variant Cs2 SnCl6 :x Sb exhibits a broadband orange-red emission, with a photoluminescence quantum yield (PLQY) of 37%. The photoluminescence of Cs2 SnCl6 :x Sb is caused by the ionoluminescence of Sb3+ within Cs2 SnCl6 matrix, which is verified by temperature dependent photoluminescence (PL) and PL decay measurements. In addition, the all inorganic structure renders Cs2 SnCl6 :x Sb with excellent thermal and water stability. Finally, a white light-emitting diode (white-LED) is fabricated by assembling Cs2 SnCl6 :0.59%Sb, Cs2 SnCl6 :2.75%Bi and Ba2 Sr2 SiO4 :Eu2+ onto the commercial UV LED chips, and the color rendering index (CRI) reaches 81.
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Chemical sensing through photonic crystal fiber: sulfuric acid detection
Etu PODDER, Md. Bellal HOSSAIN, Rayhan Habib JIBON, Abdullah Al-Mamun BULBUL, Himadri Shekhar MONDAL
Front. Optoelectron.. 2019, 12 (4 ): 372-381.
https://doi.org/10.1007/s12200-019-0903-8
A photonic crystal fiber (PCF) for sensing of sulfuric acid is designed and analyzed using Comsol Multiphysics. To analyze the sensor performance, 0%, 10%, 20%, 30%, 40% H2 SO4 solution is placed into the fiber separately and then relative sensitivity, confinement loss, birefringence, effective area etc. are investigated for each solution over wavelength ranging from 0.8 to 1.8 m m. The sensor structure affords moderately high relative sensitivity and around 63.4% sensitivity is achieved for the highest concentration of H2 SO4 at the wavelength 1.5 m m in x polarization direction. This PCF model also shows zero confinement loss for all solutions of H2 SO4 over wavelength ranging from 1 to 1.35 m m and later on approximately 1.422 × 10− 17 dB/km confinement loss is found for the highest concentration of H2 SO4 at 1.5 m m wavelength. Besides, higher birefringence is attained when the concentration of sulfuric acid is lower and it is achieved 7.5 × 10− 4 at 1.5 m m wavelength. Moreover, higher sensing area is achieved at high concentration of sulfuric acid.
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Ultra-flat broadband microwave frequency comb generation based on optical frequency comb with a multiple-quantum-well electro-absorption modulator in critical state
Cong SHEN, Peili LI, Xinyuan ZHU, Yuanfang ZHANG, Yaqiao HAN
Front. Optoelectron.. 2019, 12 (4 ): 382-391.
https://doi.org/10.1007/s12200-019-0915-4
In this paper, we proposed a novel ultra-flat broadband microwave frequency comb (MFC) generation based on optical frequency comb (OFC) with a multiple-quantum-well electro-absorption modulator (MQW-EAM) in critical state. The scheme is simple and easy to adjust. The performance of the MFC generation scheme is investigated using software Optisystem. The results show that the comb spacing of MFC can be adjusted from 5 to 20 GHz by changing RF signal’s frequency and the MFC is almost independent on the linewidth of the tunable laser diode. The performance of the MFC can be improved by reasonably increasing the voltage of the RF, the small-signal gain of the Erbium-doped fiber amplifier (EDFA) and the responsivity of the photodetector. The MFC generated by this scheme has 300 GHz effective bandwidth with 15 comb lines, whose power variation is 0.02 dB, when the components’ parameters in the Optisystem are set as follows: the power of tunable laser diode (TLD) is 0 dBm, the wavelength is 1552.52 nm, and linewidth is 1 MHz; RF signal’s frequency is 20 GHz and the voltage is 10 V; the reverse bias voltage of MQW-EAM is 6.92 V; the small-signal gain of the EDFA is 40 dB; the responsivity of the photodetector (PD) is 1 A/W.
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Heuristic polling sequence to enhance sleep count of EPON
Bhargav Ram RAYAPATI, Nakkeeran RANGASWAMY
Front. Optoelectron.. 2019, 12 (4 ): 422-432.
https://doi.org/10.1007/s12200-019-0906-5
Next-generation passive optical networks (PONs) demand power conservation to create a green environment. A reduction in power consumption of the traditional Ethernet passive optical network (EPON) can be achieved by increasing the sleep count in optical network units (ONUs). In this paper, this is accomplished by introducing a first-in-last-out (FILO) polling sequence in the place of a fixed polling sequence to increase the number of ONUs entering sleep mode (sleep count). In a fixed polling sequence, the optical line terminal (OLT) allocates idle time to the ONUs based on the overall load of the ONUs. This leads to a situation that whenever the idle time does not meet the wakeup time threshold of sleep mode, the ONUs are put into doze/active mode, which consumes more power. In the FILO polling sequence, the first polled ONU in the current cycle is made to be polled last in the following cycle. Polling continues in this way, and by this rearrangement, the idle time of delayed poll ONUs increases; hence, it helps to reduce the power consumption. Additionally, a modified load adaptive sequence arrangement (MLASA) method is suggested, where the ONUs are categorized into doze ONUs and sleep ONUs. A numerical simulation of the FILO polling sequence with a vertical cavity surface emitting laser (VCSEL) ONU shows a maximum reduction in power consumption of 15.5 W and a 20% improvement in energy savings compared with the traditional fixed polling sequence. The MLASA method results in better power consumption with minimum delay than that of the proposed FILO and existing LASA methods.
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