Investigation Of Preparationand Properties For CIGS Quaternaryceramic Targets

Cu（In₁-x Gax）Se₂（CIGS） thin film solar cells have been regarded as one of the most promising photovoltaic cells with the prospectfor mass industrial production because of their excellent performances. Large area and uniform CIGS absorbers and solar cells with stable performances can be obtained easily by a combined process of sputtering a CIGS quaternary target followed by an annealing treatment. Therefore, this approach is suitable for the industrial requirements, and the obtaining of high quality CIGS targets is the key to this approach. In order to get high quality CIGS targets for sputtering use, the influences of the variables of hot pressure sintering on the properties of the CIGS targets have been systematically investigated and the mechanism of sintering defects has been analyzed. Based on the acquirement of high quality CIGS targets, a novel idea for fabricating Na doped CIGS targets have been proposed and realized based on large quantity of exploring research. Further an innovative method for fabricating CIGS absorbers and solar cells has also been propounded. The CIGS absorbers could be directly obtained by sputtering a Se-rich CIGS target followed by an annealing process in a common atmosphere without toxical and corrosive Se-containing gas or vapor. And the approach for preparing Se-rich CIGS targets has been studied. The main research works and results are as follows:CIGS quaternary targets were fabricated by sintering processwith mixed powders of Cu₂Se, In₂Se₃ and Ga₂Se₃. The influences of powder size, sintering temperature, sintering pressure and sintering duration on the density, compositions, structures and morphologies of the CIGS targets were studied systematically. The flawless CIGS target with a highest density of 96.4% was achieved under the optimized sintering conditions.Since the delamination, fracture, and surface flaking of the CIGS targets occurred during sintering process, the mechanisms of generation of these defects were closely investigated and the mechanism model was proposed. Some liquid intermediate phases with low melting pointbrought out during the sintering process, and these liquid phases, which weaken grain boundary, extended along the grain boundaries of CIGS drove by sintering pressure. The defects would appear when the liquid phases extends and connects.Na doped CIGS targets were fabricated by hot pressure sintering with Cu2 Se, In₂Se₃, Ga₂Se₃ and Na F mixed powders. The results show that the additional Na can promote the crystallization of the CIGS targets, and Na doped CIGS targets with a high density were obtained in the Na F content range of 0.1? 0.5 mol% which should cover the optimized amount of Na in CIGS absorbers. A Na doped CIGS target with a highest density of 96.4% was achieved by the sintering process. The excessive Na F resulted in delamination of the CIGS target. The reason for this is the excess Na would segregate on the grain boundaries of CIGS in the form of Na2 Sex which weaken the CIGS grains boundary. Due to the existence of Na2 Sex on the grain boundaries the liquid phases would easily extend along the grain boundaries of CIGS and causes the delamination.Se-rich CIGS targets were fabricated by hot pressure sintering with CIGSand Se mixed powders. The results show that the additive Se can promote the crystallization of CIGS and increase the density of CIGS targets. A Se-rich CIGS target with a highest density of 98.3% was achieved by the sintering process.The Se-rich CIGS absorbers with appropriate electronic properties for the fabrication of solar cells were achieved by sputtering a Se-rich CIGS target followed by an annealing process in a N2 atmosphere. CIGS cell devices were fabricated by this approach and a highest conversion efficiency of 8.95% was finally obtained.