solar cell application-2





Design guidelines of periodic Si nanowire arrays for solar cell application

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optimum periodic Si nanowire SiNW arrays are designed via simulation for solar cell application, in terms of the structural parameters, e.g., the array periodicity P and SiNW diameter D. It is found that the more efficient light absorption compared to that of the Si thin film with the same thickness could be realized when P is between 250 and 1200 nm. Further, the ratio of D to P should be 0.5 or more specifically 0.8 for the optimized solar energy harvesting. The underlying physics is also discussed in this work.

Thanks to their uniquely combined optical and electrical characteristics, Si nanowire SiNW arrays have received considerable attention for solar cell application.Especially low grade Si raw materials can be utilized when integrating the SiNW arrays, as the light absorption and photogenerated carrier extraction processes can be decoupled,which is beneficial to lower the manufacturing cost. The enhanced light absorption by SiNW arrays has been demonstrated empirically due to the efficient antireflection to the incident light, especially in the high energy regime of the solar spectrum.It is also observed that periodic SiNW arrays are desirable for such a purpose.11 Recently, the impact of the SiNW length and diameter on the optical characteristics of the SiNW arrays is reported based on a fixed array periodicity The simulation results show that the excellent light absorption close to 100% is achievable in the high energy region of the solar spectrum in agreement with the experimental results.9,10 It further indicates that the total solar energy harvesting of the SiNW arrays in the energy region of 1–4 eV, covering the major energy range of the solar spectrum, is lower than that of the Si thin film with the same thickness due to the poor light absorption in the low energy region of the solar spectrum 2 eV, though it is observed that the light trapping capability can be improved with the SiNW diameter. As will be seen in the following analysis, the overall-inferior light absorption of the above-mentioned SiNW arrays can be attributed to their relatively small feature, i.e., the short periodicity of 100 nm.



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