TiO2 Nanoparticle/SiO2 Composite Back Reflector for Solar Cells

We have investigated a scattering back reflector(BR) using a TiO2 nanoparticles(NPs)/SiO2 composite film. The binder SiO2 is made from Perhydropolysilazane(PHPS), which is a an organosilicate polymer consisting of cyclic (SiH2-NH)n units. The PHPS changes into pure SiO2 by heat treatment less than 450 °C, which can be easily coated on a substrate by spin coat. Compare to the conventional organic binders, SiO2 is quite stable and has a good transparency. The composite BR showed more than 90% of absolute reflectance at near infrared region. To improve a passivation property of BR, we inserted a thin liquid source SiO2 layer between the silicon surface and the composite BR. The composite BR using Al coated TiO2 NPs showed high effective lifetime with a combination of thin SiO2 passivation layer. This paper describes the light reflection property of TiO2 NPs/SiO2 composite film and the effect of inserting thin liquid source SiO2 passivation layer between the silicon surface and the composite BR layer on effective lifetime.