Nongeminate Radiative Recombination and V _oc in Organic Solar Cells Enhanced by a Charge Transporter/Absorber...

Area of Science:

• Materials Science
• Photovoltaics
• Organic Electronics

Background:

• The fluorescence quantum yield (FQY) is a critical factor limiting open-circuit voltage (Voc) and efficiency in single-junction solar cells.
• Nonradiative recombination often dominates over radiative recombination, hindering efficiency gains through fluorescence enhancement.

Purpose of the Study:

• To investigate methods for enhancing FQY in completed organic solar cells (OSCs).
• To explore the impact of interfacial engineering on FQY and quasi-Fermi level splitting (QFLS).

Main Methods:

• Fabrication of PM6:Y6 organic solar cells with and without an ultrathin LiF layer.
• Measurement of FQY and characterization of interfacial properties.
• Analysis using the two-diode model to assess QFLS and Voc.

Main Results:

• Completed PM6:Y6 OSCs exhibited an FQY one order of magnitude higher than the blend alone.
• Incorporation of a LiF layer enhanced FQY by 18% by reducing interfacial oxygen acting as electron traps.
• This FQY enhancement led to a significant increase in QFLS and a measured Voc gain of 12 mV.

Conclusions:

• Interfacial modification with LiF is an effective strategy to boost FQY and Voc in OSCs.
• The observed enhancement in QFLS through FQY improvement is a promising pathway for other single-junction solar cells with interfacial radiative recombination.