Micro-photoluminescence spectroscopy on heavily-doped layers of silicon solar cells

We report and explain the photoluminescence spectra emitted from silicon solar cells with heavily-doped layers at the surface. A micro-photoluminescence spectroscopy system is employed to investigate the total spectrum emitted from both the heavily-doped layer and the silicon substrate with micron-scale spatial resolution. The two regions of the device give rise to separate photoluminescence peaks, due to band-gap narrowing effects in the highly-doped layer. Two key parameters – the absorption depth of the excitation wavelength, and the sample temperature – are shown to be critical to reveal the separate signatures from the two regions. Finally, this technique is applied to locally diffused and laser-doped regions on silicon solar cell pre-cursors, demonstrating the potential value of this micron-scale technique in studying and optimizing locally doped regions.