Defect Analysis of Monolithic GaInP/GaInAs/Ge Triple-Junction Solar Cells by Luminescence Technology

摘要

The luminescence of solar cell gives unique signatures of the bandgap and cell composition. Electroluminescence (EL) and photoluminescence (PL) of the monolithic GaInP/GaInAs/Ge triple-junction solar cells are investigated to probe the quality of each subcell. The band-to-band emissions from GaInP, GaInAs, and Ge junctions are observed at the wavelengths of 0.7, 0.9, and 1.8 μm, respectively. The emission from tunneling junction and defects are also characterized. By adjusting the excitation wavelength, PL spectra can probe individual subcell. EL spectra can measure spectral uniformity and defect level of individual subcell with selected filter. PL and EL mapping with selected filter corresponding to relative emission wavelength range can help to determine the spatial uniformity, defect, and hot spots of individual layer. The PL and EL emission spectra are corresponding to absorption edge and temperature coefficient. PL complementary to EQE measurement can give a quick look of the current matching for cell design.