B192+Numerical simulation of BaSi2 homojunction solar cells+李飞

Numerical simulation of BaSi2 homojunction solar cells  The n+-BaSi2/p-BaSi2(500 nm)/p+-BaSi2 homojunction thin-film solar cell has obtained 0.28% cell efficiency experimentally, but the cell efficiency is far from the theoretical value of BaSi2 material.  There is no further explanation in theory about the defects of p+-BaSi2/n-BaSi2 homojunction solar cell devices.  We use SCAPS-1D simulation software to simulate the window layer and absorber layer of p+-BaSi2/n-BaSi2 solar cells, respectively, and explain the mechanism of the effect of absorber layer defects and window layer on device performance. Introduction Research background and device design Conclusion: ⚫ The maximum efficiency of P+-BaSi2/n-BaSi2 homojunction solar cells is close to 26%. ⚫ The maximum opening voltage of P+-BaSi2/n-BaSi2 homojunction solar cell is about 0.85 V, and the maximum current is about 34mA/cm2. ⚫ The introduction of the n+-BaSi2 buffer layer in the device structure of p+-BaSi2/n-BaSi2/n+-BaSi2/n+-Si effectively reduces the efficiency loss caused by the energy band mismatch and defects caused by the n+-Si substrate. ➢ As the thickness of the window layer increases, the current of the battery device is significantly reduced, because the increase in the thickness of the window layer leads to more recombination centers. This increases the leakage current of the device. ➢ When the thickness of the window layer is about 20nm, the efficiency of p+-BaSi2/n-BaSi2 is close to 26% . The absorber layer is generally thicker than the window layer. In order to maintain the performance of the device, we need the absorber layer to have a lower carrier concentration, which requires our absorber layer to have a low defect concentration. It can be seen from the figure that when the defect concentration of the absorber layer is close to 1× 1015cm-3, the open circuit voltage, current, FF and efficiency of the P+-BaSi2/n- BaSi2 homojunction solar cell are all decreasing. ➢At a lower carrier concentration in the absorption layer, the carrier concentration in the window layer will not affect the performance of the device. ➢When the carrier concentration in the absorption layer is higher, the carrier concentration in the window layer increases, and the efficiency of the device increases significantly, but the current will decrease to a certain degree at this time. This may be due to the increase in carrier concentration in the absorber layer, which increases the series resistance. The effect of carrier concentration on device performance The influence of window layer thickness on device performance Optimization of the absorption layer Fei Li, Weijie Du, Yiwen Zhang Key Laboratory of Optoelectronic Material and Device, Mathematics and Science College, Shanghai Normal University 200234, China 18275448352@163.com ◆ Suitable forbidden band width ~1.3 eV ◆ absorption coefficient a~ 3 × 104 cm-1 ◆ minority carrier lifetime ~ 10 μs ◆ minority carrier diffusion length 10 mm ➢The addition of n+-Si substrate makes the theoretical efficiency of the device drop directly from 25.47% to 12.16%. In order to avoid the formation of a potential barrier region between the n+-Si substrate and n- BaSi2, the carrier transport is hindered, resulting in unsatisfactory device theoretical efficiency. ➢We designed the device structure of p+-BaSi2/n-BaSi2/n+-BaSi2/n+-Si and simulated it, and found that the introduction of the n+-BaSi2 buffer layer effectively reduced the energy band caused by the n+-Si substrate Mismatches and efficiency losses due to defects. Figure 1 BaSi2 is composed of abundant reserves of Ba and Si. Figure 1 BaSi2 is a common indirect bandgap semiconductor, but its energy state near the bottom of the conduction band changes more slowly. Compared with common indirect bandgap semiconductors, the probability of direct transitions in BaSi2 is greatly increased. BaSi2 has the property of large absorption coefficient of direct band gap semiconductor. n-BaSi2 p-BaSi2 Rear electrode Transparent conductive electrode Transparent conductive electrode n-BaSi2 i-BaSi2 p-BaSi2 Rear electrode Light Light (a) (b) Figure 2 1E16 1E17 1E18 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 E ff (%) N D n-BaSi 2 (cm-3) NA=1E+18 cm -3 NA=5E+18 cm -3 NA=1E+19 cm -3 NA=5E+19 cm -3 1E16 1E17 1E18 68 70 72 74 76 78 80 82 84 86 FF (%) N D n-BaSi 2 ( cm -3 ) NA=1E+18 cm -3 NA=5E+18 cm -3 NA=1E+19 cm -3 NA=5E+19 cm -3 1E16 1E17 1E18 17 18 19 20 21 22 23 24 J sc ( mA/cm 2 ) N D n-BaSi 2 ( cm -3 ) NA=1E+18 cm -3 NA=5E+18 cm -3 NA=1E+19 cm -3 NA=1E+19 cm -3 1E16 1E17 1E18 0.65 0.70 0.75 0.80 0.85 0.90 V oc (V) N D n-BaSi 2 ( cm -3 ) NA=1E+18 cm -3 NA=5E+18 cm -3 NA=1E+19 cm -3 NA=5E+19 cm -3 (a) (c) (d) (b) 50 100 150 200 5 10 15 20 25 E ff (%) p + -BaSi 2 (nm) NA=1E+18cm -3 NA=5E+18cm -3 NA=1E+19cm -3 NA=5E+19cm -3 50 100 150 200 0.73 0.74 0.75 0.76 0.77 0.78 V oc (V) p + -BaSi 2 (nm) NA=1E+18cm -3 NA=5E+18cm -3 NA=1E+19cm -3 NA=5E+19cm -3 50 100 150 200 5 10 15 20 25 30 35 J sc ( mA/cm 2 ) p + -BaSi 2 (nm) NA=1E+18 cm -3 NA=5E+18 cm -3 NA=1E+19 cm -3 NA=5E+19 cm -3 50 100 150 200 82.0 82.5 83.0 83.5 84.0 FF (%) p + -BaSi 2 (nm) NA=1E+18cm -3 NA=5E+18cm -3 NA=1E+19cm -3 NA=5E+19cm -3 （a） （d） （b） （c） 500 1000 1500 2000 2500 3000 3500 4000 19.2 19.3 19.4 19.5 19.6 19.7 19.8 19.9 20.0 Eff(%) n-BaSi 2 Thick ( nm ) 500 1000 1500 2000 2500 3000 3500 4000 26.8 27.0 27.2 27.4 27.6 27.8 28.0 28.2 28.4 28.6 J sc ( mA/cm 2 ) n-BaSi 2 Thick(nm) 500 1000 1500 2000 2500 3000 3500 4000 85.52 85.54 85.56 85.58 85.60 85.62 85.64 FF(%) n-BaSi 2 Thick(nm) 500 1000 1500 2000 2500 3000 3500 4000 0.810 0.815 0.820 0.825 0.830 0.835 0.840 V oc （V） n-BaSi 2 Thick(nm) (c) (b) (d) (a) Figure 3 +-窗口层 吸收层 Sun Light n-BaSi2 P+-BaSi2 n-Sin+-BaSi2 (a) (b) 0.0 0.2 0.4 0.6 0.8 -15 -20 -25 -30 -35 -40 -45 E FF =17.51 % E FF =12.16 % Current density ( mA/cm 2 ) Voltage (V) E FF =25.47 % 窗口层 吸收层 Sun Light n-BaSi2 P-BaSi2