Organic solar cells are promising for technological applications, as they are lightweight and mechanically robust. This study presents flexible organic solar cells that are less than 2 μm thick, have very low specific weight and maintain their photovoltaic performance under repeated mechanical deformation.

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Ultrathin and lightweight organic solar cells with high flexibility

Flexible CIGS, CdTe and a-Si:H based thin film solar cells: A review

An amorphous silicon solar cell on a periodic nanocone back reflector with a high 9.7% initial conversion efficiency is presented. The optimized back-reflector morphology provides powerful light trapping and enables excellent electrical cell performance. Up-scaling to industrial production of large-area modules should be possible using nanoimprint lithography.

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High‐Efficiency Amorphous Silicon Solar Cell on a Periodic Nanocone Back Reflector

We investigate amorphous silicon (a-Si:H) thin film solar cells in the n-i-p or substrate configuration that allows the use of nontransparent and flexible substrates such as metal or plastic foils such as polyethylene- naphtalate (PEN). A substrate texture is used to scatter the light at each interface, which increases the light trapping in the active layer. In the first part, we investigate the relationship between the substrate morphology and the short circuit current, which can be increased by 20% compared to the case of flat substrate. In the second part, we investigate cell designs that avoid open-circuit voltage (Voc) and fill factor (FF) losses that are often observed on textured substrates. We introduce an amorphous silicon carbide n -layer (n-SiC), a buffer layer at the n/i interface, and show that the new cell design yields high Voc and FF on both flat and textured substrates. Furthermore, we investigate the relation between voids or nanocrack formations in the intrinsic layer and the textured substrate. It reveals that the initial growth of the amorphous layer is affected by the doped layer which itself is influenced by the textured substrate. Finally, the beneficial effect of our optical and electrical findings is used to fabricate a-Si:H solar cell on PEN substrate with an initial efficiency of 8.8% for an i -layer thickness of 270 nm. © 2008 American Institute of Physics.

/pdf/optimization-of-amorphous-silicon-thin-film-solar-cells-for-ek4btdqzjh.pdf

Optimization of amorphous silicon thin film solar cells for flexible photovoltaics

SUMMARY
It is well known that current fossil fuel usage is unsustainable and associated with greenhouse gas production. The amount of the world's primary energy supply provided by renewable energy technologies is urgently required. Therefore, the relevant technologies such as hydrogen fuel, solar cell, biotechnology based on nanotechnology, and the relevant patents for exploiting the future energy for the friendly environment are reviewed. At the same time, it is pointed out that the significantly feasible world's eco-energy for the foreseeable future should not only be realized, but also methods for using the current energy and their by-products more efficiently should be found correspondingly, alongside technologies that will ensure minimal environmental impact. Copyright © 2011 John Wiley & Sons, Ltd.

Green nanotechnology of trends in future energy: a review

Recent advances in very high frequency plasma enhanced CVD process for the fabrication of thin film silicon solar cells

Micromorph silicon (a-Si:H/pc-Si:H) tandem solar cells on Asahi U-type substrates have been fabricated by very high frequency (VHF) PECVD in a high vacuum multichamber system called ASTER. The microcrystalline silicon (μc-Si) intrinsic layer (i-layer) was deposited using a shower head cathode at high pressures and under silane depletion conditions, at a high deposition rate of about 0.5 nm/s. The best optoelectronic quality μc-Si i-layer was found at the transition phase from amorphous to crystalline. An initial efficiency of 9.9% for a single junction μc-Si cell in a p-i-n configuration on texture-etched ZnO:Al was achieved. We measured a stabilized efficiency of 10% (Voc = 0.52V, FF = 0.74) after light soaking. The best tandem efficiency based on this single cell was achieved with 12% initial and 11.4% stabilized values. To fully exploit the benefit of the high stability of the μc-Si single junction cell, we made micromorph cells with a bottom cell limited structure. These tandem cells delivered an initial efficiency of 10.3% (Voc = 1.32V, FF = 0.69). To further study the independent influences of light illumination and thermal heating, annealing treatment was carried out for such μc-Si:H single junction cells and tandem cells. It was found that light soaking does not increase recombination in the μc-Si:H i-layer, and annealing treatment can improve the cell contact.

Development of highly stabilized efficiency micromorph tandem solar cells

Pressure (p) and inter-electrode distance (d) are important parameters in the process of depositing hydrogenated nanocrystalline silicon (nc-Si:H) by very high frequency plasma enhanced chemical vapour deposition (VHF PECVD). High quality nc-Si:H materials are normally deposited at high pressure (1 mbar <p <7 mbar). However, systematic research on the combined effects of p and d is rare. In order to optimize nc-Si:H for solar cells, such effects are investigated for a silane-hydrogen discharge at high pressure conditions. All nc-Si:H layers were deposited at fixed hydrogen dilution ratio (H2/SiH4), power and frequency. With optical emission spectroscopy, direct images taken by a photo camera and by 1D SiH4/H2 plasma simulation, three different series were analyzed to study the combined effects of p and d at high pressure. The effects on the crystalline ratio and the porosity of the deposited silicon layers were also investigated. When the p ·d product is constant, the plasma sheath becomes relatively thinner when d increases. When p or d increases independently, the electron density decreases. All the above modifications can increase the deposition rate, but by different mechanisms. When nc-Si:H is deposited at a p ·d product of 30 mbar·mm, compact material with high crystalline ratio is obtained

Y. Liu

Papers

Recent advances in very high frequency plasma enhanced CVD process for the fabrication of thin film silicon solar cells

Development of highly stabilized efficiency micromorph tandem solar cells

Effects of pressure and inter-electrode distance on deposition of nanocrystalline silicon under high pressure conditions