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We discuss approaches to approaches to synthesis of high efficiency low cost photovoltaics that employ single crystal GaAs and Si in thin film and wire array formats. A common theme is the use of lift-off processes that enable cell fabrication without consumption of a thick crystalline wafer per cell. Use of single crystal materials enables the achievement of high open circuit voltages relative to...
Alta Devices, Inc. has fabricated a thin-film GaAs device on a flexible substrate with an independently-confirmed solar energy conversion efficiency of 27.6%, under AM1.5G solar illumination at 1 sun intensity. This represents a new record for single-junction devices under non-concentrated sunlight. This surpasses the previous record, for conversion efficiency of a single-junction device under non-concentrated...
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...
Low aspect-ratio Si nano-hemisphere array surface texturing compatible to thin film based solar cells is studied systematically for performance improvement. The light reflection can be significantly suppressed through varying the nano-hemisphere dimensions due to the spatial effective refractive index modulation. Owing to the excellent light trapping and also the nature of low aspect ratio (critical...
The efficiency of thin film silicon solar cells critically depends on the optical absorption. In this work, we numerically investigate the light trapping effect in the weak absorption regime for 1.5 μm thick crystalline silicon at normal incidence. Using electromagnetic simulations, we study the impact of different textures on the light absorption enhancement in two-dimensional (2D) device configuration...
In this work we present 17.1%-efficient p-type single crystal Si solar cells with a multi-scale-textured surface and no dielectric antireflection coating. Multi-scale texturing is achieved by a gold-nanoparticle-assisted nanoporous etch after conventional micron scale KOH-based pyramid texturing (pyramid black etching). By incorporating geometric enhancement of antireflection, this multi-scale texturing...
Thin film chalcogenide kesterites Cu2ZnSnS4 and Cu2ZnSnSe4 (CZTSSe) are promising candidates for the next generation thin film solar cells. They exhibit a high natural abundance of all constituents, a high absorption coefficient and a tunable direct bandgap between 1.0–1.5 eV. A prerequisite for the use of CZTSSe as absorber layers in photovoltaic applications on large scales is a detailed knowledge...
This report outlines improvements to the energy conversion efficiency in wide bandgap (Eg>1.2 eV) solar cells based on CuIn1−xGaxSe2. Using (a) alkaline containing high temperature glass substrates, (b) elevated substrate temperatures 600°C-650°C and (c) high vacuum evaporation from elemental sources following NREL's three-stage process, we have been able to improve the performance of wider bandgap...
The goal of this work is to investigate the influence of the Na incorporation method into CuIn1−xGaxSe2 (x=Ga/(In+Ga)) (CIGSe)-based solar cells on polyimide (PI) foil. In particular we want to compare the effect of a NaF precursor layer with that of NaF co- and post-deposition. Secondary ion and neutral mass spectroscopies (SIMS/SNMS) are used to study the distribution of the elements through the...
The variation observed in rf-plasma cracked radical Se (R-Se) source grown Cu(In, Ga)Se2 (CIGS) film properties and conventional evaporative Se (E-Se) source grown CIGS film properties was studied for the development of industrial production techniques of evaporated CIGS films and CIGS texture control techniques, which are important for the optimization of the CIGS/buffer layer interface to yield...
AgCu(InGa)Se2 alloy absorber layers with various Ga/(Ga+In) and Ag/(Ag+Cu) ratios were deposited using multi-source elemental evaporation and analyzed by glancing incidence x-ray diffraction and energy dispersive x-ray spectroscopy. All films exhibit satellite chalcopyrite reflections in the x-ray diffraction pattern and films with 0.5 ≤ Ga < 1 and Ag > 0.5 have additional reflections consistent...
The literature describes various techniques for fabricating thin monocrystalline Si films without the need of sawing. Layer transfer using epitaxy on porous Si (PSI) and subsequent layer separation from the growth substrate is one particular attractive option. A 40 μm thick epitaxial Si cell from this so-called PSI process is capable of saving about 80 % of the Si that is consumed by a 180 μm-thick...
A record independently confirmed production cell efficiency of 19.3% is presented for a large area P-type CZ silicon solar cell, based on the UNSW laser doped selective emitter technology. In this work, the innovative and patented laser doping technology is simply added to a standard Centrotherm turnkey line, operating with a modified process and the addition of the laser doping and light induced...
A back-contact back-junction silicon solar cell is presented that was exclusively structured and metalized by screen-printing technology. On n-type base material the emitter was formed by locally printed and alloyed aluminum structures in a co-firing process. By a varying emitter coverage on the rear the influence on the collection probability and thus the short-circuit current density is analyzed...
Innovalight™ previously described an industrially viable approach to fabricate selective emitter (SE) cells based on screen-printed Silicon Ink. In this report we describe the performance of these cells incorporated into photovoltaic modules fabricated at Hanwha SolarOne (formerly Solar-Fun) in Qidong, Jiangsu Province, China. We demonstrate the conservation of the performance gain of Silicon Ink...
To increase the competitiveness of HIT (Heterojunction with Intrinsic Thin-layer) solar cells, we have been working on the enhancing their conversion efficiency. This time, we improved the heterojunction of the HIT solar cell, which made it possible to enhance the cell conversion efficiency. In addition, we have developed module technologies such as a new tab design and anti-reflection coated glass...
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