Overcoming Carrier Concentration Limits in Polycrystalline CdTe Thin Films with In Situ Doping

Area of Science:

• Materials Science
• Solid State Physics
• Photovoltaics

Background:

• Thin film photovoltaic materials like cadmium telluride (CdTe) promise lower costs than silicon.
• Controlling charge carrier concentration in these materials has been a long-standing challenge.
• Intrinsic defects limit the performance of polycrystalline thin films.

Purpose of the Study:

• To improve the performance of cadmium telluride (CdTe) solar cells.
• To overcome limitations in controlling hole and electron concentration in CdTe films.
• To achieve higher solar cell efficiencies through enhanced doping.

Main Methods:

• In-situ doping with antimony (Sb), arsenic (As), and phosphorus (P).
• Post-growth annealing treatments.
• Characterization of carrier concentration and lifetime in thin polycrystalline CdTe films.

Main Results:

• Successfully increased hole density in CdTe films from 10^14 cm^-3 to 10^16-10^17 cm^-3.
• Maintained carrier lifetimes in the nanosecond range.
• Demonstrated a viable method for enhancing CdTe thin film properties.

Conclusions:

• In-situ doping and annealing effectively control charge carrier concentration in CdTe.
• This method enables higher solar cell efficiencies, potentially reaching 25%.
• Advances in CdTe photovoltaics can lead to costs competitive with conventional energy sources.