All screen-printed 18% homogeneous emitter solar cells using high volume manufacturing equipment

The Innovalight Cougar^™ Platform is a portfolio of simple to implement technologies that, when combined with Innovalight Silicon Ink, enables the manufacture of a selective emitter solar cell with a non-masking single-step diffusion. Cell efficiencies of up to 19% have been achieved. Innovalight Silicon Ink is a highly engineered silicon nanoparticle colloidal dispersion, implemented for both high volume ink-jet and screen deposition, and further optimized to be produced and delivered in commercial volumes. To compare the advancement of the Innovalight Cougar Platform against a standard process, a screen-printed solar cell structure with a homogeneous 50-60Ω/sq emitter, has been developed. It uses standard production equipment and closely mirrors the process typically used by photovoltaic manufactures today. In an effort to emulate the best cells currently in production, we have advanced the reference cell through surface texture, both acidic (ISO) and random pyramids, and diffusion optimization using in-line and tube diffusion. The tube diffusion has an advantage, over in-line processing, in open-circuit voltage (V_OC) of 9mV and fill factor of 0.9% resulting in an increase in efficiency by 0.4% absolute for the ISO texture process. Comparing tube diffused ISO to random pyramid textured substrates, a difference in V_OC of +4mV and short-circuit current (J_SC) of +2.3mA/cm² was found without a loss in fill factor for the random pyramid textured substrates. This results in an efficiency gain of 1.1% absolute to a 17.8% median. Additionally, we successfully demonstrated scaling the substrate size from 125mm to 156mm for this process flow without affecting the cell performance and achieving equivalent efficiency of 18%.