Solar Cells Based on PTB7-Fx: PC₇₁BM Active Layer Processed with Two Types of Solvent Additives and Sputtered Ag...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) offer a promising alternative to conventional photovoltaics due to their flexibility and low manufacturing costs.
• The performance of OSCs is highly dependent on the morphology and properties of the active layer, which is typically composed of a donor and an acceptor material.
• Solvent additives are often employed during the fabrication of the active layer to control morphology and improve device efficiency.

Purpose of the Study:

• To investigate the effect of two solvent additives, diiodooctane (DIO) and triethyl phosphate (TEP), on the performance of organic solar cells based on PTB7-Fx:PC71BM.
• To analyze how these additives influence the thin-film morphology, optical properties, and charge transport characteristics of the active layer.
• To compare the performance of devices fabricated with and without solvent additives.

Main Methods:

• Fabrication of organic solar cells with varying PTB7-Fx (x = 0, 20, 100) donor materials and PC71BM acceptor.
• Spin-coating of the active layer from dichlorobenzene solutions with and without 3% DIO and 1% TEP.
• Device characterization including optical properties, thin-film morphology analysis, current density-voltage (J-V) measurements, and impedance spectroscopy.

Main Results:

• PTB7-Fx:PC71BM solar cells processed with DIO and TEP exhibited similar absorption and quantum efficiency spectra compared to devices without additives.
• DIO additive preferentially dissolved the fullerene acceptor, enhancing fill factor, impedance spectra, charge carrier transport, and collection.
• TEP additive preferentially dissolved the copolymer donor, leading to a more refined morphology of the thin-film active layers.

Conclusions:

• Solvent additives DIO and TEP can be used to fine-tune the morphology and performance of PTB7-Fx:PC71BM organic solar cells.
• DIO positively impacts charge transport and collection efficiency, while TEP refines the active layer morphology.
• The study demonstrates that strategic use of solvent additives can lead to comparable or improved performance in organic photovoltaic devices without compromising optical properties.