Dilute Donor Organic Solar Cells Based on Non-fullerene Acceptors

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Small molecule non-fullerene acceptors (NFAs) have advanced organic photovoltaic (OPV) devices.
• Efficient OPVs typically use a bulk heterojunction (BHJ) with near-equal donor/acceptor ratios, posing manufacturing challenges.
• Developing OPVs with reduced donor or acceptor content is advantageous for scalability.

Purpose of the Study:

• To investigate the performance of OPV devices with low donor content using PM6 as the donor and Y6 or ITIC-4F as NFAs.
• To understand the factors limiting efficiency in such low-donor-content BHJ systems.
• To explore the relationship between film morphology, optical properties, and device performance.

Main Methods:

• Fabrication of OPV devices with varying weight ratios of the polymeric donor PM6 and NFAs (Y6 or ITIC-4F), specifically exploring a 1:10 donor:acceptor ratio.
• Characterization of device performance, including photoconversion efficiency.
• Analysis of charge mobility, recombination rates, film absorption coefficient, and interfacial morphology.

Main Results:

• OPV devices with a 1:10 donor:acceptor weight ratio achieved significant photoconversion efficiencies of approximately 6% (with Y6) and 5% (with ITIC-4F).
• Device efficiency was found to be primarily dependent on the film absorption coefficient and the interfacial surface area for exciton dissociation.
• Charge mobility and recombination rates showed minimal impact on the overall device efficiency.

Conclusions:

• Low donor content OPVs utilizing high-performance NFAs can achieve competitive efficiencies.
• Optimizing film absorption and maximizing interfacial area are crucial for efficient exciton dissociation in these systems.
• This work highlights a promising strategy for scalable and efficient organic photovoltaic device fabrication.