Solution-Processable Organic Molecule for High-Performance Organic Solar Cells with Low Acceptor Content.

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) offer a promising alternative to traditional silicon-based photovoltaics due to their flexibility and low manufacturing costs.
• Developing efficient and stable donor materials is crucial for advancing OSC performance.
• Planar D-A-D-A-D structured molecules are of interest for their potential to enhance charge transport and light absorption.

Purpose of the Study:

• To design and synthesize a novel planar D2-A-D1-A-D2 organic molecule, BDT-BTF, for use as a donor material in OSCs.
• To investigate the photovoltaic properties and performance of OSCs incorporating the synthesized BDT-BTF.
• To understand the relationship between molecular structure, film morphology, and device performance.

Main Methods:

• Synthesis of the BDT-BTF organic molecule.
• Fabrication of organic solar cells using BDT-BTF as the donor material and PC71BM as the acceptor.
• Characterization of the BDT-BTF material, including absorption spectra, energy levels, and charge carrier mobility.
• Device performance testing (Voc, Jsc, FF, PCE).
• Morphological analysis using transmission electron microscopy (TEM).

Main Results:

• The synthesized BDT-BTF molecule exhibits broad visible light absorption, a suitable highest occupied molecular orbital (HOMO) energy level (-5.20 eV), and high hole mobility (1.07 × 10⁻² cm²/V s).
• OSCs fabricated with BDT-BTF and PC71BM achieved a power conversion efficiency (PCE) of 5.88%, with an open-circuit voltage (Voc) of 0.85 V, short-circuit current density (Jsc) of 10.48 mA/cm², and fill factor (FF) of 0.66.
• TEM analysis revealed an optimal interpenetrating network in the BDT-BTF:PC71BM blend, facilitating exciton dissociation and charge transport.
• The optimized D/A weight ratio of 3:1 represents the lowest acceptor content reported for high-performance OSCs.

Conclusions:

• The planar D2-A-D1-A-D2 structured BDT-BTF is a promising high-performance donor material for solution-processable organic solar cells.
• The molecular design, characterized by high coplanarity and strong crystallinity, significantly contributes to the material's favorable electronic and charge transport properties.
• The achieved performance highlights the potential of BDT-BTF in developing efficient and cost-effective organic photovoltaic devices with reduced acceptor material usage.