π-π stacking induced high current density and improved efficiency in ternary organic solar cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Ternary blend systems are crucial for enhancing organic solar cell (OSC) performance, specifically short-circuit current density (JSC) and fill factor (FF).
• Identifying suitable third components with complementary light absorption and energy level alignment remains a significant challenge in OSC development.

Purpose of the Study:

• To design and synthesize a novel small organic molecule, DFNPy, for use as a third component in ternary blend OSCs.
• To investigate the impact of DFNPy on the optical, morphological, and photovoltaic properties of OSCs.

Main Methods:

• Synthesis of the small organic molecule DFNPy, featuring a triphenylamine core and pyrene rings.
• Fabrication and characterization of ternary blend OSCs using PTB7-Th:DFNPy:PC71BM.
• Analysis of absorption spectra, film morphology, charge transfer, and photovoltaic performance.

Main Results:

• DFNPy exhibits complementary absorption in the 350-450 nm range, a region less explored in ternary OSCs.
• The pyrene rings in DFNPy promote charge transfer through π-π stacking.
• Ternary OSCs incorporating DFNPy achieved a high power conversion efficiency (PCE) of 10.59% and an enhanced JSC of 19.72 mA cm-2.
• DFNPy improved film morphology, leading to better phase separation, crystallinity, charge generation, and reduced recombination, ultimately enhancing charge mobility.

Conclusions:

• DFNPy is an effective third component for ternary blend OSCs, significantly improving photovoltaic performance.
• The molecular design of DFNPy, with its complementary absorption and π-π stacking capabilities, offers a promising strategy for advancing OSC technology.
• Optimizing film morphology through the addition of DFNPy is key to enhancing charge dynamics and overall device efficiency.