Seminari Gruppo Fisica della Materia

Laser-Induced Doping in Modern Crystalline Silicon Solar Cells

by Dr Kejun Chen (Colorado School of Mines - National Renewable Energy Laboratory)

Europe/Rome
1/2-2 - Aula C (Dipartimento di Fisica e Astronomia - Edificio Marzolo)

1/2-2 - Aula C

Dipartimento di Fisica e Astronomia - Edificio Marzolo

100
Description

Crystalline silicon (c-Si) is the dominant photovoltaic semiconducting material for the production of solar cells and modules, with a current market share of about 95%. During the manufacturing of silicon solar cells, laser processing is widely used for its excellent material selectivity, low cost, and fast speed. Important examples include laser scribing for edge isolation and cutting large cells in half; laser-doping for selective emitters; and rear contact openings by laser ablation for the passivated emitter and rear cells (p-PERC), a current workhorse for the PV industry. To further increase the cell efficiency, solar cells with passivating contacts - consisting of a heavily doped poly-Si and a thin tunneling oxide – are readily gaining PV market share. In this talk, I present the collaboration work between NREL and University of Padova on the novel application of laser-induced doping in the poly-Si layer to achieve non-equilibrium doping above the dopant's solid solubility limit in Si (hyperdoping). The doping diffusion profiles, as well as electrical performance were analyzed through secondary ion mass spectrometry (SIMS), Van der Pauw-Hall measurement, photoconductive lifetime spectroscopy, and contact resistivity studies. Advanced spectroscopy techniques such as scanning spreading resistance microscopy and Kelvin probe force microscopy were employed to explore at a greater depth of the transport properties of the laser-processed samples. Our work provides insights into hyperdoping with laser processing of other semiconductors with atoms that may otherwise have a low solubility. This technology may not only enable the next generation of high-efficiency c-Si photovoltaics technology but could also greatly benefit the c-Si integrated circuit industry.

Organised by

Enrico Napolitani