Papers by Keyword: Local Defect

Abstract: The effect of local molecular structural cavity defect on the atom frequencies of bonded atoms is investigated in this study. The molecular dynamic (MD) simulation method is used to simulate the variation of atom frequency near by the cavity defect in a carbon diamond structure. The potential energy model, i.e. the second-generation reactive empirical bond order (REBO) potential function, is employed to derive the dynamic interaction between bonded atoms. The effect of local defect on the vibration amplitude and the density of state (DOS) is studied. The simulated results indicate that the local defect may affect the dynamic behavior of atoms near the local cavity defect significantly.

Abstract: If there are local defects in the solar cell module, the output efficiency of the module will decrease. This article introduces the detection of local defect of solar cell module based on the infrared image technology. It finally establishes an image library which contains some infrared images of seven kinds of defects and a basic standard which can judge the quality of the module. The reasons of some defects are listed in the article. The unqualified rate will greatly decrease for the technique. The research is helpful to eliminate the module that contains recessive defects. The life of the modules also will be extended.

Abstract: PN junction is one of the most important parts of solar cells. Its quality affects lifetime and efficiency of solar cells. Local defects which appear in PN junctions during the manufacture process are very important from this point of view. These are caused by localized areas with high donor or acceptor doping agents, impurities, dislocations or other mechanisms which effect in lower breakdown voltage of PN junction in reverse bias. Several base methods can be used for solar cells nondestructive diagnostics. Measuring methods of low-band noise current effective value with reverse bias junction were used in this paper. This method allows detection of local defects and volume degradation in PN junctions of solar cells and it can be used for detection of microplasma noise. This noise is an impulse noise and it is caused by local avalanche breakdowns in small area of the junction. It can be recognized by two or more level random square current pulses with constant height, random appearance time and random pulse length. Information about these effects can be used in noise diagnostics of structural defects of PN junctions and then it can be used for quality and lifetime estimation of samples with these parameters.

Abstract: This article discusses the issue of noise measurements application for the quality assessment of the solar cells themselves and production technology alike. The main focus of our research is the random n-level (in most case just two-level) impulse noise, usually referred to as microplasma noise. This noise was found to be in a direct consequence of local breakdowns in micro-sized regions and brings about a reduction of lifetime or a destruction of the pn junction. Non-destructive measurement methodology as presented here is suitable for testing of a large number of various semiconductor devices not only for solar cells. In this paper experimental measurement of noise signals in the frequency and time domain is presented. Furthermore the microplasma noise behaviour and defect geometry is discussed.