CIGS Solar Cell Research
Why is solar cell important?
The limited world of oil stocks makes us turn to seek new and renewable energy sources. One of the abundant energies and easy to obtain is solar energy. Solar cells are the perfect solution for harvesting solar energy for electricity. However, high efficiency and low production costs are a challenge. Thin film solar cell is one of the solutions to produce solar cells at low cost.
What is CIGS?
CIGS(Copper Indium Gallium Selenide) is p-type material belonging to I-III-V family which has tetragonal chalcopyrite structure. This solar cell in form of thin film gives benefit on its light weight and low material consumption. Copper indium gallium selenide (Cu(InxGa1-x)Se2, CIGS) materials have a higher light absorption coefficient. It can achieve the same absorbance, which is more advantageous in cost. CIGS solar cells can be fabricated with different methods, namely one stage sputtering using quaternary CIGS target, two stages process involving co-sputtering of precursor followed by selenization and sulfurization, and lastly three stages process using element precursors followed by selenization.
To improve device performances our lab focus on improving absorber and buffer condition by doping CIGS with metal and alkali, band gap engineer by adjusting Ga grading at rear or front side grading, replacing CdS buffer with free Cd buffer such as ZnOS and double buffer ZnOS-MgO by atomic layer deposition. The effect of alkali metal diffusion, band gap grading, absorber microstructure, crystallinity and buffer layer are carefully studied to evaluated their effect on the device performance such as Voc, Jsc, Fill factor, carrier concentration and recombination. Efficiency beyond 15% has been achieved for single step CIGS and over than 16 % for two steps CIGS. In addition our lab not only fabricated CIGS on rigid substrate but also on flexible substrate.
