Understanding and implementation of rapid thermal technologies for high-efficiency silicon solar cells
Rapid and potentially low-cost process techniques are analyzed and successfully applied toward the fabrication of high-efficiency monocrystalline Si solar cells. First, a methodology for achieving high-quality screen-printed (SP) contacts is developed to achieve fill factors (FF's) of 0.785--0.795 on monocrystalline Si. Second, rapid emitter formation if accomplished by diffusion under tungsten halogen lamps in both beltline and rapid thermal processing (RTP) systems (instead of in a conventional infrared furnace). Third, a combination of SP aluminum and RTP is used to form an excellent back surface field (BSF) in 2 min to achieve an effective back surface recombination velocity (S{sub eff}) of 200 cm/s on 2.3 {Omega}-cm Si. Next, a novel dielectric passivation scheme (formed by stacking a plasma silicon nitride film on top of a rapid thermal oxide layer) is developed that reduces the surface recombination velocity (S) to approximately 10 cm/s on the 1.3 {Omega}-cm p-Si surface. The essential feature of the stack passivation scheme is its ability to withstand short 700--850 C anneal treatments (like the ones used to ire SP contacts) without degradation in S. The stack also lowers the emitter saturation current density (J{sub oe}) of 40 and 90 {Omega}/sq emitters by a factor of three and ten, respectively, compared to no passivation. Finally, the above individual processes are integrated to achieve (1) {gt}19% efficient solar cells with emitter and Al-BSF formed by RTP and contacts formed by vacuum evaporation and lift-off, (2) 17% efficient manufacturable cells with emitter and Al-BSF formed in a beltline furnace and contacts formed by SP, and (3) 17% efficient gridded-back contact (bifacial) cells with surface passivation accomplished by the stack and gridded front and back contacts formed by SP and cofiring.
- Research Organization:
- Georgia Inst. of Tech., Atlanta, GA (US)
- OSTI ID:
- 20006066
- Journal Information:
- IEEE Transactions on Electron Devices (Institute of Electrical and Electronics Engineers), Vol. 46, Issue 10; Other Information: PBD: Oct 1999; ISSN 0018-9383
- Country of Publication:
- United States
- Language:
- English
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