Imperfections in a solar emitter, a critical layer that collects the current-producing charge carriers in a solar cell, causes significant efficiency loss in most of the commercial solar cells. Picasolar’s Hydrogen Super Emitter (HSE) perfects emitters after cells are already made, helping to use less silver, avoid multiple processing steps and disruptions, and improve efficiency gains. The HSE is a one-step, low-temperature process that electrically deactivates 99.5% of the dopants at the surface of the solar cell. This significantly lowers surface recombination, or the charge carrier losses experienced in the surface layer of a solar cell, thus helping to make the solar cells more efficient. In addition, Picasolar will create a tool that uses this new process and will integrate it into a high volume manufacturing line.
The HSE approach uses significantly less silver, which is the second most expensive component in solar cell processing, and is a technology that can also be used for creating high efficiency solar cells. This project will determine all necessary process changes needed to take full advantage of the HSE technology while demonstrating compatibility with current industry standard n-type cell technologies. Mini-modules will be fabricated to show that HSE requires no changes to standard encapsulation and interconnection techniques. These mini-modules will be used to demonstrate that HSE enhanced panels pass all relevant industry reliability testing. A pilot tool will also be built, certified, installed and tested in a high volume manufacturing line.
One main factor limiting solar cell performance is the quality of the front surface. The front surface quality is dependent on the dopant concentration, with increasing dopant density meaning decreased performance. While traditional selective emitters have light doping at the surface for increasing efficiency, they also require more silver because the conductivity of the emitter is low. The HSE technique avoids this trade-off with high overall emitter conductivity while achieving surface doping that’s much lower than traditional approaches. In addition, the atomic hydrogen can mitigate defects at the surface and in the bulk of the cell, helping to create solar cells with higher efficiency and with lower costs.