P. C. Tseng

Combined micro- and nano-scale surface textures for enhanced near-infrared light harvesting in silicon photovoltaics

As silicon photovoltaics evolve towards thin-wafer technologies, efficient optical absorption for the near-infrared wavelengths has become particularly challenging. In this work, we present a solution that employs combined micro- and nano-scale surface textures to increase light harvesting in the near-infrared for crystalline silicon photovoltaics, and discuss the associated antireflection and scattering mechanisms. The surface textures are achieved by uniformly depositing a layer of indium-tin-oxide nanowhiskers on micro-grooved silicon substrates using electron-beam evaporation. The nanowhiskers facilitate optical transmission in the near-infrared by functioning as impedance matching layers with effective refractive indices gradually varying from 1 to 1.3. Materials with such unique refractive index characteristics are not readily available in nature. As a result, the solar cell with combined textures achieves over 90% external quantum efficiencies for a broad wavelength range of 460-980 nm, which is crucial to the development of advanced thin-substrate silicon solar cells.

Enhanced angular characteristics of indium tin oxide nanowhisker-coated silicon solar cells.

Omnidirectional and broadband light harvesting is critical to photovoltaics due to the suns movement and its wide spectral range of radiation. In this work, we demonstrate distinctive indium-tin-oxide nanowhiskers that achieve superior angular and spectral characteristics for crystalline silicon solar cells using angle-resolved reflectance spectroscopy. The solar-spectrum weighted reflectance is well below 6% for incident angles of up to 70° and for the wavelength range between 400nm and 1000nm. As a result, the nanowhisker coated solar cell exhibits broadband quantum efficiency characteristics and enhanced short-circuit currents for large angles of incidence.

Efficiency Enhancement in Single-Junction InGaP Solar Cells by Using Self-Assembled Nanospheres

A single-junction InGaP solar cells with polystyrene (PS) nanospheres on the surface has been developed. The self-assembly of PS nanospheres is one of the simplest and the fastest methods with which to build a 2D closely packed periodic structure. Based on the scattering of the PS nanospheres, the light path length can be increased. As compared to the InGaP solar cells without PS nanospheres on the top surface the standard process. An increase short-circuit current form 8.93% to 10.31% is improved when a single-junction InGaP solar cells with PS nanospheres. The conversion efficiency measured can also be improved from 8.79% to 9.71%. The single-junction InGaP solar cell with PS nanospheres was achieved.

Compound surface textures for enhanced near-infrared light havesting of crystallin silicon solar cells

As silicon photovoltaics evolve towards thin-wafer technologies, efficient optical absorption for the near-infrared wavelengths has become particularly challenging. In this work, we present a solution that employs combined micro- and nano-scale surface textures to increase light harvesting in the near-infrared for crystalline silicon photovoltaics, and discuss the associated antireflection and scattering mechanisms. The surface textures are achieved by uniformly depositing a layer of indium-tin-oxide nanowhiskers on micro-grooved silicon substrates using electron-beam evaporation. The nanowhiskers facilitate optical transmission in the near-infrared by functioning as impedance matching layers with effective refractive indices gradually varying from 1 to 1.3. Materials with such unique refractive index characteristics are not readily available in nature. Compared to the reflectance of the conventional silicon solar cell, the combined textures structure provided broadband high absorption, especially in the near infrared region. As a result, the solar cell with combined textures achieves over 90% external quantum efficiencies for a broad wavelength range of 460 to 980 nm, which is crucial to the development of advanced thin-substrate silicon solar cells. Due to the high photocurrent contributed to the performance, the compound textured solar cell increased the 1.1% absolute power conversion efficiency, from 16.1% to 17.2%.

Large-scale and enhanced efficiency C-Si solar cell with moth-eye-like by using self-assembled lithography

We demonstrated the Si solar cell with ladder-shaped nanorod array, fabricated by combined the self-assembled lithography and reactive-ion etching technique. The measurement of angular reflective spectrums of the solar cell with ladder-shaped nanorod array using an integration sphere remained lower at broadband spectra and large angle of incident compared to the solar cell with micro-textured surface. The I–V measurement shown the current density and conversion efficiency could be improved by the ladder-shaped nanorod array. The enhancement conversion efficiency approached to 34.54%.

Efficiency enhancement InGaP/GaAs dual-junction solar cell with sub-wavelength antireflection nanorod arrays

The enhanced conversion efficiency of the InGaP/GaAs dual-junction solar cell was demonstrated antireflection nanorod arrays. After self-assembled Ni clusters ,the nanorod arrays were fabricated by inductively-coupled-plasma reactive ion etching. The conversion efficiency were measured under one-sun air mass 1.5 global illuminations at room temperature. The short current of the nanorod arrays cell was enhanced 10.0% and the efficiency was enhanced 10.8%. We were also studied the light absorption efficiencies of the top InGaP and bottom GaAs cells under the influence of nanorod arrays. Surface nanorod arrays were not only as antireflection layers but also scattering sources. The nanorod arrays structure can be significant improved the maximum conversion efficiency.

Efficiency enhancement in single junction ingap solar cells by using self-assembled nanospheres

A single-junction InGaP solar cell with polystyrene (PS) nanospheres on the surface has been developed. The self-assembly of PS nanospheres is one of the simplest and the fastest methods with which to build a 2-D closely packed periodic structure. Due to the scattering of the PS nanospheres, the light path length can be increased when compared to the InGaP solar cells without PS nanospheres on the top. An increase short-circuit current from 8.93 to 10.31 mA is improved when a single-junction InGaP solar cell is coated with PS nanospheres. The conversion efficiency measured can also be improved from 8.79% to 9.71%. The single-junction InGaP solar cell with PS nanospheres was achieved.