29 research outputs found
Advanced surface texturing for silicon solar cells
The multi-crystalline silicon (me-Si) solar cell is considered to be one of the most
promising cells capable of achieving high efficiency at low cost and high reliability.
Improving solar cells efficiency using low cost materials requires careful design
considerations aiming to minimise the optical and electrical losses. In this work plasma
texturing was employed to reduce optical reflections from silicon surfaces well below
1%.
Plasma texturing is used to form light trapping structures suitable for silicon solar cells.
Several plasma texturing methods are investigated and associated defects are analysed.
Masked as well as mask-less texturing techniques are investigated. Conventional parallel
plate Reactive Ion Elching (RIE), Inductively Coupled Plasma (ICP) and Electron
Cyclotron Resonance (ECR) plasma system are used to compare the plasma induced
defects in silicon. The influence of various plasma etch parameters on plasma induced
defect is investigated. A correlation between the minority carriers lifetime and surface
area increased by texturing is established.
Effective lifetime measurements using Quasi Steady State Photo Conductive (QSSPC)
technique is mainly used to estimate the plasma induced defect in textured silicon
substrates. Sinton lifetime tester is used to measure the effective lifetime of the substrates.
The implied open circuit voltage is calculated from the lifetime data for textured
substrates.
In this work low temperature photoluminescence spectroscopy is also used to analyse the
defect caused by plasma on me-Si substrates. Photoluminescence (PL) data is obtained
using the 514.5 nm line of an Ar⁺ laser as an excitation source. The luminescence is
dispersed with SPEX 1700 spectrometer with a liquid nitrogen cooled Germanium
detector.
Reflectance measurements are performed on textured surfaces usmg a purpose built
integrating sphere attachment of a high accuracy spectrophotometer. Modelling is also
performed using PV-optics software to compare the experimental and theoretical results.
Finally, silicon solar cells are fabricated with measured efficiency around 18% . The
efficiency is estimated from the I-V characteristics data obtained using a calibrated
halogen lamp and a HP semiconductor parameter analyser. Spin-on-dopant source as
well as solid diffusion source is used to form the ewitter junction of the solar cells
fabricated on p-type silicon wafers. Multicrystalline silicon, CZ- silicon and FZ silicon
wafers are used to fabricate solar cells in this thesis. The effect of single and double
layer antireflection coatings on diffused reflections is also investigated
Single crystal diamond cantilevers for mechanical control of quantum systems
We demonstrate a simple technique to fabricate cantilevers from bulk CVD sinle crystal diamond as well as from single crystal diamond membrane windows fabricated in a novel technique. Mechanical quality factors of cantilevers were measured. A mechanical Q-factor of as high as 500 was achieved.2 page(s
A 3D lateral electrode structure for diamond based microdosimetry
A diamond based microdosimeter prototype featuring a 3D lateral electrode structure was created using laser ablation and active brazing alloys and characterised by means of ion beam induced charge collection measurements and finite element analysis, using Synopsys TCAD simulation package