Study On The Irradiation Damage Behaviours And The Effects Of ZnO Window Layer Of CIGS Solar Cells

CIGS(Copper Indium Gallium Selenium) solar cells have a potential application in space because of the flexibility and high resistance to radiation. Experiments showed that CIGS degrades little after exposed to 1MeV 1×1016 e/cm2 electrons. High radiation resistance CIGS act as absorb layer. But ZnO, as the top most layer of CIGS solar cells, which should have been the most vulnerable part, have not attract enough attention. In this paper, the effects of ZnO on CIGS were studied in detail by means of radiation modificaton. I-V and QE(Quantum Efficiency) were tested for electrical degradation behavior of CIGS solar cells.D-I-V(Dark I-V)shows the increase of dark current and decrease of shunt resistance. XPS and XRD were used to detect the damage induced by radiation, Reflection test were used to study the mechanism of degradation.1MeV electrons were used to cause ionization damage through the solar cell. Electron radiation causes the decrease of Isc which further result in the decay of Uoc. 1 MeV electrons affact Cd S layer at the same time. CIGS changes little after radiation, which confirm its high radiation resistance. D-I-V indicated addition of series resistance which could happens during irridation.50ke V protons affect ZnO, Cd S and CIGS by SRIM calculation. The Uoc and Isc degradation accelerates as the energy of particles increases. 500 nm damage peak is related to Cd S and 600 nm peak is associated with the interface between Cd S and CIGS. Damage around 390 nm may be attributed to the destruction of ZnO windows layer, which is much serious than 1MeV electrons. By compare of EQE and IQE, the drop of Isc mainly is attributed to degradation of optical properties of ZnO, Cd S and interface between Cd S and CIGS deteriorate simultaneously.50ke V 60° were used to further decrease the inject range and it is found that QE and reflection change much compared with 50 ke V 60°. wx AMPS simulation shows that increase of reflection lead to the drop of Isc and Uoc, causing averaged decay of EQE. Electron or hole traps cause the degradation of Isc and FF, causing the decrease of EQE at shorter wavelength region, while Uoc changes little. Series resistance lead to decrease of Isc and FF, while the Uoc is almost unchanged. Series resistance does not affect the EQE. Simulation results are in good accordance with experiments, which further indicates the significance of ZnO windows layer.