Realistic Efficiency Limits for Singlet-Fission Silicon Solar Cells.

Area of Science:

• Photovoltaics
• Materials Science
• Physical Chemistry

Background:

• Singlet fission is a promising mechanism for enhancing solar cell efficiency.
• It involves the conversion of a high-energy singlet exciton into two lower-energy triplet excitons.
• This process offers a pathway to overcome the Shockley-Queisser limit in silicon solar cells.

Purpose of the Study:

• To calculate the theoretical efficiency potential of silicon solar cells utilizing singlet fission.
• To investigate the impact of singlet energy and entropic gain on device performance.
• To compare different triplet exciton transfer mechanisms within singlet fission solar cells.

Main Methods:

• Computational modeling of singlet fission processes in silicon solar cells.
• Analysis of three distinct triplet exciton transfer pathways: charge transfer, Dexter transfer, and Förster resonance energy transfer (FRET).
• Parametric studies exploring the influence of singlet energy levels and entropic factors on maximum achievable efficiency.

Main Results:

• Maximum theoretical efficiencies were calculated for three singlet-fission silicon solar cell implementations.
• Charge transfer mechanism yielded a maximum efficiency of 34.6% at a singlet energy of 1.85 eV.
• Dexter transfer and FRET mechanisms showed maximum efficiencies of 32.9% (at 2.15 eV) and 28.0% (at 2.33 eV), respectively.
• Efficiency gains from singlet fission are amplified in more efficient base silicon cells.

Conclusions:

• Singlet fission holds significant potential for dramatically increasing silicon solar cell efficiency.
• The choice of triplet exciton transfer mechanism and the singlet energy level are critical for optimizing performance.
• The synergistic effect of singlet fission with high-efficiency silicon bases presents a compelling avenue for next-generation photovoltaics.