A novel processing technology for high-efficiency silicon solar cells
- Georgia Inst. of Tech., Atlanta, GA (United States). Dept. of Electrical and Computer Engineering
- Filmtronics, Inc., Butler, PA (United States)
A novel simultaneous boron and phosphorus diffusion technique is presented to produce simple, high-efficiency n{sup +}pp{sup +} silicon solar cells in one thermal cycle. This technique uses boron and phosphorus spin-on dopant films to fabricate limited solid doping sources out of dummy silicon wafers. This approach results in the delivery of a fixed dose of P{sub 2}O{sub 5} or B{sub 2}O{sub 3} to the diffused sample. The resulting diffusion glass is extremely thin ({approximately}60 {angstrom}), which allows for the in situ growth of a passivating thermal oxide without increasing the solar cell reflectance. Reverse saturation current density (J{sub o}) measurements show that the in situ oxide passivation for a light boron and phosphorus diffusion provides excellent passivation properties, resulting in J{sub o} values in the 100 FA/cm{sup 2} range. Measurements of the bulk minority carrier lifetime show that by fabricating separate boron solid sources, trace impurities in the spin-on dopant film are not transported to the diffused sample. This filtering action is shown to result in bulk lifetimes in excess of 1 ms for silicon doped indirectly from the source wafers but gives much lower lifetimes ({approximately}6 {micro}s) for the wafers on which the boron spin-on film was directly applied. This process was validated by fabricating in situ oxide passivated, n{sup +}pp{sup +} solar cells in one high-temperature cycle incorporating several high-efficiency features including surface texturing and a back side reflector, resulting in confirmed efficiencies in the 19--20% range.
- Sponsoring Organization:
- Sandia National Labs., Albuquerque, NM (United States)
- OSTI ID:
- 345395
- Journal Information:
- Journal of the Electrochemical Society, Journal Name: Journal of the Electrochemical Society Journal Issue: 3 Vol. 146; ISSN 0013-4651; ISSN JESOAN
- Country of Publication:
- United States
- Language:
- English
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