Process optimisation for coloured laser grooved buried contact solar cells

The use of photovoltaic modules in architectural applications is now firmly established and large modules of glass-glass construction produced specifically for the BIPV market are available. However, the range of solar cell colours and shapes currently offered by suppliers is still very limited and this is a barrier to the widespread use of PV modules as constructional components. Initial investigations of the colour and efficiency of Laser Grooved Buried Contact (LGBC) solar cells as a function of the thickness of the LPCVD silicon nitride antireflection coating were reported in the late 1990s, but the subsequent commercialisation of coloured cell products has been limited in part by the difficulty in controlling the uniformity and reproducibility of colour in large scale cell production. The aim of the present work is to understand and control the processes that affect the thickness and hence colour of the silicon nitride ARC. Process conditions were optimised to enable the formation of antireflection coatings with thicknesses in the range 90 nm to 400 nm. LGBC solar cells were fabricated in 5 colours on both non-textured Cz and partially textured multicrystalline wafers. Good uniformity of colour was achieved both across individual cells and throughout whole process runs. Laser scribing was used to produce cells in a range of shapes which, in conjunction with the choice of colours, demonstrates the potential for novel BIPV applications.