1. 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

2. 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*10 16 cm -3 – Fill Factor > 60% – Efficiency > 5% – Drop in Efficiency after light soaking of no more than 10%

3. 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

4. Staebler-Wronski Effect

5. 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

6. Questions