Ping Yang

Radial n-i-p structure SiNW-based microcrystalline silicon thin-film solar cells on flexible stainless steel

Radial n-i-p structure silicon nanowire (SiNW)-based microcrystalline silicon thin-film solar cells on stainless steel foil was fabricated by plasma-enhanced chemical vapor deposition. The SiNW solar cell displays very low optical reflectance (approximately 15% on average) over a broad range of wavelengths (400 to 1,100 nm). The initial SiNW-based microcrystalline (μc-Si:H) thin-film solar cell has an open-circuit voltage of 0.37 V, short-circuit current density of 13.36 mA/cm2, fill factor of 0.3, and conversion efficiency of 1.48%. After acid treatment, the performance of the modified SiNW-based μc-Si:H thin-film solar cell has been improved remarkably with an open-circuit voltage of 0.48 V, short-circuit current density of 13.42 mA/cm2, fill factor of 0.35, and conversion efficiency of 2.25%. The external quantum efficiency measurements show that the external quantum efficiency response of SiNW solar cells is improved greatly in the wavelength range of 630 to 900 nm compared to the corresponding planar film solar cells.

Improved open-circuit voltage of silicon nanowires solar cells by surface passivation

The surface recombination at the surface of silicon nanowires (SiNWs) deteriorates the performance of SiNWs solar cells and thus the reduction of the SiNWs surface recombination becomes a crucial issue. In this paper, we observe an improved SiNW surface passivation by hydrogenated amorphous silicon (a-Si:H). The results show that a thicker i-layer results in a higher open-circuit voltage Voc. That can be ascribed to the better passivation by thicker intrinsic a-Si:H. The dark current–voltage data reveal that the reverse leakage current and the diode ideality factor at high forward bias decrease monotonically with increasing the thickness of i-layer. Moreover, for the first time, we observe that the lower Voc is associated with the capacitance–voltage (C–V) curve shifting toward higher positive voltage. We propose that the shift of the curve is related to the capacitance affected by the surface states. Finally we prove that the improvement in the NW solar cell performance, especially the Voc, can be attributed to the reduction of the surface states on SiNWs.

The Amorphous/Crystalline Silicon Interface Research of HIT Solar Cells by Simulation

In this paper, we have focused on the influence of interface state density and band offsets on the performance of HIT solar cells by simulation. The interface state density Dit have negative influence on the open-circuit voltage VOC, fill factor FF and the short circuit current JSC, beyond different Dit respectively. VOC decreases monotonically with increasing Dit only when Dit is greater than 1010 cm-2, and for FF and JSC Dit is 1012 cm-2, 1013 cm-2, respectively. Observed reduction in VOC (Dit is from 1×1010 cm-2 to 5×1013 cm-2) may be due to the enhanced recombination possibility, which diminishes the difference in quasi Fermi energies from 0.8 eV to 0.46 eV. Reduction of JSC (Dit is from 1×1013 cm-2 to 5×1013 cm-2) is connected with the carrier recombination rate that is heightened from 2.43×1024cm-3/s to 3.1×1026cm-3/s, which is markedly by two orders of magnitude. In addition, our research results demonstrate that by increasing the conduction band offset EC (from 0.09eV to 0.15 eV), the VOC could be increased by 15.9 mV, while the performance of HIT solar cells is not affected by the valence band offset EV. The increase of EC results in the rising of Vbi and thus improves VOC. It is worth mention that, the recombination potential VRe could be decreased from 232 meV to 208 meV by the increase of EC (from 0.09eV to 0.15eV) and thus is favorable to VOC. Consequently, when the interface state density is less than 1010 cm-2 and the conduction band offset reaches 0.15eV, we can optimize the performance of HIT solar cells to achieve 24.95% efficiency.

Improvement of Silicon Nanowires Solar Cells by Removing Residual Catalytic Indium

We demonstrate the improvement of silicon nanowires (SiNWs) solar cells by acid treatments of SiNWs. This leads to open-circuit voltage (Voc) increase, which is related to reduced dark current.

Effect of Assets of Silicon Film Passivation Layer on the Performance of Silicon Nanowire Solar Cells

Silicon film as a surface passivation layer is reported to reduce surface recombination on silicon nanowires (SiNWs) and thus enable to improve SiNW solar cell (SC) performance. A question yet to be answered regards the link between the silicon film assets and the solar cell performances. We investigated the effect of the properties of silicon films on the SiNWs SC performances by adjusting hydrogen dilution. Our results showed that the open-circuit voltage (Voc) and short-circuit current density (Jsc) of SiNWs SC increase until hydrogen dilution 10 and then decrease. An open-circuit voltage of 0.397 V and short-circuit current density of 18.42 mA/cm2 are achieved at optimized hydrogen dilution. Based on the analysis of silicon film properties we proposed that the increase of defect density with hydrogen dilution was the main cause for the deterioration of SiNWs SC performance.

Improvement of n/i interface layer properties in microcrystalline silicon solar cell

Properties of n-i interface are critical for hydrogenated microcrystalline silicon (μc-Si:H )substrate-type (n–i–p) solar cell as it affects carrier collection, which is visible in the red response . Here, we report a remarkable improvement in visible-infrared responses upon hydrogen plasma treatment （HPT）of n/i interface. We demonstrate that hydrogen plasma treatment in the initial stage of a μc-Si:H i layer growth affects the red response of μc-Si:H solar cell. At the optimal deposition condition, 18% higher short-circuit current density was obtained than its count part without using HPT

Determination of the Interface States in Amorphous/Crystalline Silicon Using Surface Photovoltage Spectroscopy

The interface state level at amorphous/crystalline silicon (a-Si:H/c-Si) heterojunctions is identified with surface photovoltage spectroscopy (SPS). A positive slope alteration of SPS in 1.2 eV indicates there is a primarily empty state at Ev(c-Si)+0.75 eV. Using hydrogen plasma treatment (HPT) on c-Si surface, we observed a systematic variation in the SPS signal upon HPT time, which was associated to the change of interface state density. Our results show that the SPS can be used to optimize the heterojunction with intrinsic thin-layer solar cell preparation process.

Improvement of microcrystalline silicon N-I-P solar cell by hydrogen plasma treatment for n/i interface

The performance of a nip microcrystalline silicon (μc-Si) solar cell was improved by “alternately deposition and hydrogen plasma treatment method (ADHT)” at n/i interface. The defect densities measured by static capacitance-voltage (C-V) was decreased from 2.37×10¹⁶ cm⁻³ to 1.25 ×10¹⁶ cm⁻³. The short-circuit current Jsc was improved from 14.5 mA/cm² to 17.2 mA/cm² on bared stainless steel substrate and Obtained 24.7 mA/cm² on a.BR substrates.