LED作为量子效率仪中单色光的可行性研究

随着LED技术的不断进步，已发展出多种波长的大功率LED，不用昂贵的单色仪，而采用各种波长的LED作为单色光来制造量子效率仪；也不需要旋转滤色片轮切换滤色片来避免光栅单色仪中高级次光谱的影响。LED作为单色光，可实现无机械运动、测量速度快、故障率低的优点。多只LED焊接在PCB上形成离散型光源，无法采用常规的椭球面反射镜、透镜或凹面反射镜进行汇聚。采用高反射率反射镜片制备成锥形光导管，将离散型光源发出的光汇聚为一个小光斑，可以很好地解决离散型光源汇聚难的问题，同时实现了高的光利用率。通过测量LED的波峰值、半峰宽和稳定性，并与传统的卤素灯和氙灯为光源的传统量子效率仪进行比较，发现单色光的波峰值与量子效率的测量准确性是正相关的，波峰值越高，测量的准确性越高；半峰宽在5.1~9.5 nm范围内，半峰宽对测量的准确性没有影响。采用LED、卤素灯和氙灯量子效率仪分别测试同一块太阳电池的量子效率，计算相同波段的积分电流，与世界先进的氙灯量子效率仪相比，相对偏差为0.34%，与卤素灯量子效率仪的相当，说明半峰宽在5.1~55.7 nm范围内，测量准确性与半峰宽无明显的相关性；LED的不稳定度为0.4%，介于氙灯和卤素灯之间。从这几个方面来看，LED是可以作为单色光用于量子效率的测试。

Feasibility Study on LED as Monochromatic Light Source in Quantum Efficiency Instrument

With the continuous development of light emitting diode (LED) technology, high-power LEDs with various wavelengths have been developed, therefore we can design a LED-based QE instrument using LED with various wavelengths as monochromatic light source instead of expensive monochrometers. Compared with the traditional QE instrument, there is no filter required in the LED-based QE instrument, so it is not necessary to rotate the filter wheel for a grating monochrometer to avoid the influence of high-order spectrum. Without mechanical movements, which reduces the failure rate and speeds up the measurement. Several LEDs are welded on a printed circuit board (PCB) as the discrete light source. However, it is impossible to converge light as the traditional QE instrument using ellipsoidal mirror, lens or concave mirror. Therefore, the discrete light from the LED board is collected and homogenized into a small spot by a light pipe formed with highly reflective reflectors, which can solve the difficulty in converging discrete light sources and the high utilization ratio of light is achieved. By measuring the peak intensity, full width at half maxima (FWHM) and stability of LED, and further comparing it with the traditional QE instrument using halogen lamp and xenon lamp as light source, it is found that the measurement accuracy of QE is positively correlated with the peak intensity of monochromatic light. The higher the peak intensity is, the higher the measurement accuracy is. Furthermore, it is also observed that the measurement accuracy has no obvious correlation with FWHM in the range of 2.5~9.5 nm. The QE of the same solar cell is measured by LED-based, halogen lamp-based and xenon lamp-based QE instrument, respectively. The integrated current is further calculated based on QE in the same wave range, and compared with that obtained from the advanced xenon lamp-based QE instrument, it is found that the relative error of the LED-based QE instrument is only 0.34%, which is equivalent to the accuracy of the halogen lamp-based QE instrument. Based on integrated current conditions, the measurement accuracy has no obvious correlation with the FWHM of LED varies from 8.3~55.7 nm. Moreover, the instability of LED is 0.4%, which is between xenon lamp and halogen lamp. Based on these three aspects, it can be concluded that LED can be used as the monochromatic light source for QE measurement.