Enhanced light trapping in solar cells using snow globe coating

Abstract

A novel method, snow globe coating, is found to show significant enhancement of the short circuit current JSC (35%) when applied as a scattering back reflector for polycrystalline silicon thin-film solar cells. The coating is formed from high refractive index titania particles without containing binder and gives close to 100% reflectance for wavelengths above 400 nm. Snow globe coating is a physicochemical coating method executable in pH neutral media. The mild conditions of this process make this method applicable to many different types of solar cells. Copyright © 2012 John Wiley & Sons, Ltd.

Combined plasmonic and dielectric rear reflectors for enhanced photocurrent in solar cells

“…The titania particles used in this work were found to form a stable dispersion in water at pH 6-7. 18,21,22 The morphology of the titania particles forming Snow Globe Coating is shown in Figure 1(e). The coating process is based on self-assembly by settling particles dispersed in a liquid.…”

“…In Ref. 18, we report that Snow Globe Coating alone (without MNPs) increases the Jsc by around 38% of the Lambertian case. For the combination of paint and plasmonic particles, the enhancement is 51% of the Lambertian value, while for paint only the enhancement is 22%.…”

“…The case of paint only has a relatively narrow angular distribution corresponding to 30% of the scattered light being trapped at long wavelengths, given by n eff ¼ 1.4, and a reflectance, R, of 85%, in agreement with previous results. 18 It has been previously found that Snow Globe Coating also leads to relatively narrow angular distribution (value of n eff ¼ 1.4), but with a much higher reflectance of approximately 100%. 18 We can see from Table II that combining the Snow Globe Coating with metal nanoparticles maintains the very high reflectance of the Snow Globe Coating, but substantially widens the scattering distribution, increasing the n eff to 2.6.…”

“…18 It has been previously found that Snow Globe Coating also leads to relatively narrow angular distribution (value of n eff ¼ 1.4), but with a much higher reflectance of approximately 100%. 18 We can see from Table II that combining the Snow Globe Coating with metal nanoparticles maintains the very high reflectance of the Snow Globe Coating, but substantially widens the scattering distribution, increasing the n eff to 2.6. This increases the fraction of the scattered light that is trapped at long wavelengths to 80%.…”

“…To date, we have demonstrated short circuit current (J SC ) enhancements of 35% for 2 lm thick poly-Si thin film solar cells. 18 This simple and efficient process forms a binder-free coating of dielectric particles (rutile TiO 2 , diameter: 1 lm) that provides very high reflection due to low absorption losses and high index contrast between the particles and the surrounding air.…”