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半导体材料对于激光的吸收机制主要为本征吸收,电子吸收光子能量产生跃迁,形成光生载流子,载流子也会吸收一部分激光能量,并通过弛豫碰撞进行能量交换,最终将能量传导到晶格,晶格温度升高,这种载流子系统与晶格的能量弛豫时间在皮秒量级,所以激光脉冲宽度在皮秒量级及以下时需要考虑载流子通过弛豫碰撞的能量交换时间。皮秒激光作用下,半导体材料晶格的温度升高在载流子温度升高之后,即到皮秒脉冲激光结束辐照后,激光能量还大部分处于载流子系统中。
实验中皮秒激光的脉冲宽度仅为15 ps,脉冲激光辐照结束后,激光辐照的大部分能量仍然在载流子系统中,通过弛豫碰撞将能量以热传导的形式传导到晶格,从而导致电池温度的升高。实验中所用激光器单脉冲能量较低,激光辐照结束后电池温度上升幅度较小,但是在高重频作用下,短时间内成千上万个脉冲的能量沉积使电池局部温度过高,发生熔融烧蚀损伤。
表1和2分别为不同功率皮秒激光辐照三结GaInP2/GaAs/Ge电池栅线与非栅线部位后,电池的最大功率下降情况。根据表中的数据对比发现,相比激光辐照非栅线部位,当激光辐照三结GaInP2/GaAs/Ge电池栅线时,仅0.15 mW的激光功率便导致三结GaInP2/GaAs/Ge电池产生损伤,而辐照非栅线部位时激光功率需要达到1.5 mW才能产生类似的损伤;当激光功率为150 mW时,辐照栅线电极后太阳能电池最大功率下降幅度达到94.8%,而辐照非栅线部位的下降幅度仅为27.6%。
辐照非栅线部位的表面形貌测量显示,随着激光功率的增加,激光光束中心辐照区域形成一个逐渐增大的烧蚀坑,由于激光脉宽为皮秒量级,因此形成的烧蚀坑轮廓清晰,烧蚀坑周围区域由于温度低于光电材料熔点而发生氧化还原反应,形成环状致密氧化层。电池电致发光图像显示,尽管激光光斑较小,但电池内部损伤面积随着激光功率的增加而增大。辐照栅线部位时,由于栅线电极受到激光辐照导致熔断,表面形貌测量显示,损伤面积随着激光功率的增加而变大,主要是因为栅线部位受热熔断会影响太阳能电池对载流子的吸收,降低电池的光电转换能力。因此在真空环境下,皮秒激光辐照三结GaInP2/GaAs/Ge电池栅线具有更好的损伤效果。
表 1 皮秒激光辐照三结GaInP2/GaAs/Ge电池非栅线部位最大功率下降幅度
Table 1. Maximum power reduction of three-junction GaInP2/GaAs/Ge cell irradiated by picosecond laser at the non-grid line area
Laser power/mW 1.5 15 150 1500 3750 15000 Reduction of battery power 3.4% 17.2% 27.6% 27.6% 37.9% 48.3% 表 2 皮秒激光辐照三结GaInP2/GaAs/Ge电池栅线部位最大功率下降幅度
Table 2. Maximum power reduction of three-junction GaInP2/GaAs/Ge cell irradiated by picosecond laser at the grid line area
Laser power/mW 0.15 0.75 1.5 15 150 Reduction of battery power 3.4% 65.5% 75.9% 94.1% 94.8%
Damage characteristics of solar cells irradiated by picosecond pulsed lasers (invited)
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摘要: 以皮秒脉宽激光多脉冲损伤太阳能电池为背景,通过激光烧蚀电池前后表面形貌、电池伏安特性、电致发光特性获得损伤特性。采用脉宽15 ps、波长1 064 nm皮秒脉冲激光辐照三结GaAs太阳能电池进行实验。通过重频调节改变激光辐照功率,对太阳能电池栅线与非栅线部位在激光辐照下的损伤特性进行分析。实验发现辐照非栅线部位时,尽管激光光斑较小,但电池内部材料已经发生损伤,主要是由于电池内部材料有序结构的破坏逐渐增大,尤其是激光功率越高时,内部损伤面积越大。当激光辐照栅线部位时,栅线部位受热熔断会极大影响太阳能电池对载流子的吸收,从而降低电池的光电转换能力,进而影响太阳能电池的电性能,使得激光辐照栅线部位损伤效果强于辐照非栅线部位。Abstract: Based on the background that picosecond pulse width laser with multi-pulses damaging the solar cells, we use three methods that are the surface morphology, voltammetry characteristics and electrolumi-nescence of solar cells to obtain the damage characteristics of solar cells with the laser before and after laser ablation. A three-junction GaAs solar cell with pulse width of 15 ps and wavelength of 1 064 nm is irradiated by picosecond pulsed laser. By changing the laser irradiation power through repetition frequency regulation, the damage characteristics of grid line and non-grid line of solar cell under laser irradiation are analyzed. The experimental results show that, although the laser spot is small, the material inside the battery has been damaged. It's mainly because the damage of the ordered structure of the material inside the battery is gradually increased. When the laser power is higher, the internal damage area is larger. When the gate line is irradiated by laser, the fusion of the gate line will greatly affect the absorption of the carriers by the solar cell, thus reducing the photoelectric conversion ability of the solar cell, and then affecting the electrical performance of the solar cell, so that the damage effect of the gate line is stronger than that of the non-gate line.
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表 1 皮秒激光辐照三结GaInP2/GaAs/Ge电池非栅线部位最大功率下降幅度
Table 1. Maximum power reduction of three-junction GaInP2/GaAs/Ge cell irradiated by picosecond laser at the non-grid line area
Laser power/mW 1.5 15 150 1500 3750 15000 Reduction of battery power 3.4% 17.2% 27.6% 27.6% 37.9% 48.3% 表 2 皮秒激光辐照三结GaInP2/GaAs/Ge电池栅线部位最大功率下降幅度
Table 2. Maximum power reduction of three-junction GaInP2/GaAs/Ge cell irradiated by picosecond laser at the grid line area
Laser power/mW 0.15 0.75 1.5 15 150 Reduction of battery power 3.4% 65.5% 75.9% 94.1% 94.8% -
[1] Fatemi N S, Pollard H E, Hou HQ, et al. Solar array trades between very high-efficiency multi-junction and Si space solar cells[C]//IEEE Photovoltaic Specialists Conference. IEEE, 2000. [2] Xiang X B, Du W H, Chang X L, et al. The study on high efficient AlxGa1−xAs/GaAs solar cells [J]. Solar Energy Materials and Solar Cells, 2001, 68(1): 97-103. doi: 10.1016/S0927-0248(00)00348-2 [3] Zou Yonggang, Li Lin, Liu Guojun, et al. Research progress of GaAs solar cell [J]. Journal of Changchun University of Science and Technology (Natural Science Edition), 2010, 33(1): 44-47. (in Chinese) [4] Knechtli R C, Loo R Y, Kamath G S. High-efficiency GaAs solar cells [J]. IEEE Transactions on Electron Devices, 1984, 31(5): 577-588. doi: 10.1109/T-ED.1984.21572 [5] Mukind R P. Spacecraft Power Systems[M]. New York: CRC Press, 2005: 1023-1028. [6] Iwata H, Asakawa K. Accumulative damage of GaAs and InP surfaces induced by Multiple-Laser-Pulse irradiation [J]. Japanese Journal of Applied Physics, 2008, 47(4): 2161-2167. doi: 10.1143/JJAP.47.2161 [7] Li G, Zhang H, Zhou G, et al. Research on influence of parasitic resistance of InGaAs solar cells under continuous wave laser irradiation [J]. Journal of Physics: Conference Series, 2017, 84(4): 12-14. doi: 10.1088/1742-6596/844/1/012014 [8] Wang X, Shen Z H, Lu J, et al. Laser-induced damage threshold of silicon in millisecond, nanosecond, and picosecond regimes [J]. Journal of Applied Physics, 2010, 108(3): 33103. doi: 10.1063/1.3466996 [9] Tang Daoyuan, Xu Jianming, Li Yunpeng, et al. Damage effects of tri-junction GaAs solar cells irradiated by continuous-wave laser in vacuum [J]. Aerospace Shanghai, 2020, 37(2): 54-60. (in Chinese) doi: 10.19328/j.cnki.1006-1630.2020.02.007 [10] 李永富. 强激光对砷化镓材料损伤机理的研究 [D]. 山东大学, 2007. Li Yongfu. Study on damage mechanism of GaAs material by intense laser [D]. Jinan: Shandong University, 2007. (in Chinese) [11] 祁海峰. 连续及纳秒激光对砷化镓材料的损伤研究 [D]. 山东大学, 2008. Qi Haifeng. Research on surface damage of GaAs induced by continuous and nanosecond pulse laser [D]. Jinan: Shandong University, 2008. (in Chinese) [12] 邱冬冬. 激光对硅太阳能电池和硅CCD的损伤效应研究 [D]. 国防科学技术大学, 2010. Qiu Dongdong. Damage effects research of silicon solar cells and silicon ccd induced by laser [D]. Changsha: National University of Defense Technology, 2010. (in Chinese) [13] Qiu Dongdong, Wang Rui, Cheng Xiang′ai, et al. Damage effect of monocrystalline silicon solar cells under ultrashort pulse laser irradiations [J]. Infrared and Laser Engineering, 2012, 41(1): 112-115. (in Chinese) doi: 10.3969/j.issn.1007-2276.2012.01.022 [14] 田秀芹. 飞秒激光照射下硅/砷化镓太阳能电池的光电特性研究 [D]. 中南大学, 2014. Tian Xiuqin. Performance research of silicon/gallium arsenide solar cells under femtosecond high power laser illumination [D]. Changsha: Central South University, 2014. (in Chinese) [15] Tian Xiuqin, Xiao Si, Tao Shaohua, et al. Damage threshold research of monocrystalline silicon solar cellsunder femtosecond laser illumination [J]. Infrared and Laser Engineering, 2014, 43(3): 676-680. (in Chinese) doi: 10.3969/j.issn.1007-2276.2014.03.002 [16] Lu Weiming, Li Xing, Zhang Fute, et al. Defect detection of solar cell based on electroluminescence and thermography imaging with different bias voltage [J]. Chinese Journal of Luminescence, 2014, 35(12): 1511-1519. (in Chinese) doi: 10.3788/fgxb20143512.1511 [17] Li Y H, Pan M, Pang A S, et al, et al. The application of electroluminescence imaging to detection the hidden defects in silicon solar cells [J]. Chinese Journal of Luminescence, 2011, 32(4): 378-382. (in Chinese) doi: 10.3788/fgxb20113204.0378 [18] Chang Hao, Chen Yifu, Zhou Weijing, et al. Damage characteristics of the solar cells irradiated by nanosecond pulsed lasers and the effects on photoelectric conversion [J]. Infrared and Laser Engineering, 2021, 50(S2): 20210296. (in Chinese) doi: 10.3788/IRLA20210296