Shi-e Yang

The simulation of physical mechanism for HTM-free perovskite organic lead iodide planar heterojunction solar cells

Recently, organo-metal halide perovskites have attracted much attention from the scientific community because of their successful application in the absorber layer of low-cost solar cells. For the further improvement of the performance of such cells, a thorough understanding of the influence of the material properties on the working mechanism of a device is very necessary and important. In this study, two-dimensional modeling of hole transport material free planar heterojunction solar cells was performed, in which electromagnetic simulation was directly linked to carrier transport calculations. An optimum absorber thickness of 200 nm was reproduced in the simulation at carrier diffusion length of 100 nm, in good agreement with previous experiments. This optimum thickness increased with the increase of diffusion length, and an efficiency of about 11% was obtained at 300 nm with a diffusion length of 300 nm. Finally, it was demonstrated that the relatively low efficiency of such solar cells was directly related to the low short-circuit photocurrent density (J SC) and the low open-circuit voltage (V OC) due to the insufficient absorption of the long-wavelength region and the nearly intrinsic doping concentration, respectively.

Broadband Absorption Enhancement in μc-Si:H Thin-Film Solar Cells Based on Silver Nanoparticle Arrays

The thin-film solar cell structure with a broadband absorption enhancement is reported. We designed spherical silver (Ag) nanoparticle arrays on or embedded partially into indium tin oxide (ITO) layer of the hydrogenated microcrystalline silicon (μc-Si:H) thin-film solar cells. The geometrical parameters, such as nanoparticle radius (R), array period (P) and ITO layer thickness (d) are optimized by using the finite element method (FEM). The numerical results show that the key parameter that influences the integrated absorption is period/radius ratio (P/R) for Ag nanoparticle arrays. Embedding nanoparticle arrays partially into ITO layer with the appropriate thickness can improve broadband light-trapping. The optimized structure shows 50.1% enhancement in the integrated absorption compared to the reference cell when P=500nm, R=100nm and d=70nm. Furthermore, physical mechanisms of absorption enhancement in different wavelength range are discussed according to the electrical field amplitude distributions in ...

The effect of deposition pressure on the surface roughness scaling of microcrystalline silicon films by very high frequency plasma-enhanced chemical vapor deposition

The scaling behaviour of surface roughness evolution of μc-Si:H prepared by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) has been investigated using spectroscopic ellipsometry (SE). The growth exponent β was compared for the film deposited under the different pressure Pg. For films deposited at Pg = 70 Pa, the growth exponent β is about.0.22, which corresponds to the definite diffusion growth. However, films deposited at Pg = 300 Pa show abnormal scaling behavior with the exponent β of about.0.81, which is much larger than 0.5 of zero diffusion limit in the scaling theory. This implies that some roughening increasing mechanism such as shadowing effect contributes to the growing surface.