Improving the Stability of Hydrogenated Amorphous Silicon Solar Cells
Team: Anthony Arrett, Wei Chen, William Elliott, Brian Modtland, and David Rincon
Advisor/Client: Dr. Vikram Dalal
Overview• Goal: to improve the stability and efficiency of a-Si:H solar cells through
annealing and graded Boron doping• Concept: PIN Solar cell deivce topology. Decrease defects (clusters)
through high annealing temps. High clusters = poor efficiency and stability• Functional Specs:
– Photoconductivity > 1*10-5 Ω-1 cm-1
– Dark Conductivity < 1*10-10 Ω-1 cm-1
– Tauc Band Gap < 1.8eV– Defect density after light soaking < 1*1016 cm-3
– Fill Factor > 60%– Efficiency > 5%– Drop in Efficiency after light soaking of no more than 10%
Background of a-Si:H
• What is a-Si:H (hydrogenated amorphous silicon)?
• Advantages of a-Si:H– Cheaper, Easy to Make– Large Area Cells
• Causes of instability in a-Si:H– Dangling Bonds created by Incident Light
• Stradins breakthrough– Less Stability over Time with High –Temp Anneal
Staebler-Wronski Effect
Our approach
• Annealing at high temperatures– Decrease dangling bond clusters
• Boron graded doping– Improve built-in field for carrier collection
• Trial and error using several different “recipes” for the production of a more stable a-Si:H device
Questions