Abstract
We describe recent progress in developing epitaxial film crystal silicon (c-Si) solar cells that can be grown at low temperature (<760 °C) on seed-on-glass substrates. This low-cost approach is enabled by rapid epitaxy (up to 300 nm/min) of Si films with low dislocation density (< 1×10 5 cm-2) at glass-compatible temperatures by hot-wire chemical vapor deposition (HWCVD). Epitaxial test cells on heavily-doped 'dead' Si wafers provide insight into the quality of the Si absorber and the physics that limit device performance. Our best 2-3 μm thick, film silicon heterojunction (c-Si/a-Si) solar cells have reached ∼6.7% efficiency (V oc ∼ 570 mV, Jsc ∼18 mA/cm-2) without rapid thermal anneal, defect passivation or light trapping. Unpassivated dislocations are strong recombination centers and limit effective minority carrier diffusion lengths to less than 15-20 μm (roughly half the distance between dislocations). We also report devices without light-trapping on layer-transfer Si seed layers bonded to display-glass; these seed layers template growth of high-quality HWCVD cSi. Our initial devices have V oc = 460 mV, Jsc = 16.2 mA/cm2, Eff. = 4.8 %, but will benefit from post-growth anneals, hydrogenation and new surface treatments before epitaxy. We discuss junction transport physics in the devices and explore the role of post-growth H-passivation and rapid thermal annealing treatments on device performance.
Original language | American English |
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Pages | 626-630 |
Number of pages | 5 |
DOIs | |
State | Published - 2010 |
Event | 35th IEEE Photovoltaic Specialists Conference, PVSC 2010 - Honolulu, HI, United States Duration: 20 Jun 2010 → 25 Jun 2010 |
Conference
Conference | 35th IEEE Photovoltaic Specialists Conference, PVSC 2010 |
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Country/Territory | United States |
City | Honolulu, HI |
Period | 20/06/10 → 25/06/10 |
NREL Publication Number
- NREL/CP-520-47740
Keywords
- epitaxial growth models
- film silicon solar cells
- glass-compatible temperatures