The simulations of quasi one-dimensional (1D) and quasi three-dimensional (3D) device process and optoelectronic performance were conducted on silicon APD array pixels using Silvaco, realizing micro region analysis of the electric field distribution, avalanche gain, and photoelectric response characteristics of the APD photosensitive region. The multiplication coefficients corresponding to different positions of APD pixel were obtained and compared with the ideal 1D device structure. The results show that the multiplication factor of the center region of APD pixel is significantly higher than that of the edge of the photosensitive region. The simulation of microlens to converge the incident light to the center of the photosensitive region confirmed the increasement of APD avalanche multiplication current, i.e. the quasi 3D structural APD response is increased from 13.6 A/W to 54.8 A/W, and the effective fill factor is increased from 20.9% to 84.2%. Thus, the utilization rate of incident light is effectively improved.
Using the frequency domain analysis method, the thermocouple time constant in the dynamic measurement of laser power is analyzed, and the pole of the thermocouple is compensated by the frequency domain analysis method, thus expanding the frequency domain range of the measurement system. On this basis, by measuring the response curve of the power detector, its time constant is determined, and its transfer function is obtained by designing a predictive circuit. The designed prediction circuit is simulated, and the optimal design parameters are obtained, which doubles the frequency response and reduces the response time constant to the step function from T to T/2. Through the test of the actual circuit, the results are basically consistent with the theoretical calculation results, which can meet the rapid detection needs of high-power detectors.
KEYWORDS: Silicon, Nanostructures, Absorption, Reflectivity, Solar cells, Silicon films, Thin film solar cells, Silicon solar cells, Diffraction gratings, Nanolithography
Enhancing the light absorption in ultrathin-film silicon solar cells is important for improving efficiency and reducing cost. In this paper, we report a highly effecient cosine periodic nanostructure as light trapping texture. The design and fabrication as well as measurement of cosine nanotextures were presented. The optimized structure yields an average reflectance of 7.07% at an equivalent silicon thickness of 10μm, much better than planar and random pyramid structures. The measurements demonstrate that the absorptions in ultrathin film solar cells are very close to the Yablonovitch limit for the entire solar spectrum and insensitive to the angle of the light. This approach is applicable to various thicknesses and promising in future glass-based thin film solar cells.
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