Achieving Optimal Bulk Heterojunction in All-Polymer Solar Cells by Sequential Processing with Nonorthogonal Solvents

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Developing efficient all-polymer solar cells (all-PSCs) faces challenges with unfavorable morphology from conventional blend casting (BC).
• Optimizing active layer morphology is crucial for enhancing power conversion efficiency in all-PSCs.

Purpose of the Study:

• To introduce sequential processing (SP) using nonorthogonal solvents as a facile method for fabricating high-performance all-PSCs.
• To investigate the impact of SP on the active layer morphology and device efficiency compared to BC.

Main Methods:

• Fabrication of all-PSCs using sequential processing (SP) with a polymer donor (PBDB-T) and a polymer acceptor (FPDI-BT1).
• Tuning solvent composition during the secondary deposition of the acceptor to achieve a bulk heterojunction-like configuration.
• Characterization of device performance, including power conversion efficiency (PCE).

Main Results:

• The SP device achieved a significantly boosted power conversion efficiency of 7.15%.
• The conventional blend casting (BC) analogue showed a PCE of 3.57%, less than half of the SP device.
• SP facilitated the intercalation of the acceptor into the donor film, creating a desirable morphology without post-processing.

Conclusions:

• Sequential processing (SP) is a promising strategy for fabricating high-performance all-PSCs with tunable active layer configurations.
• SP overcomes the morphological limitations of conventional blend casting, leading to substantial efficiency improvements.
• This method offers a facile route to high-efficiency organic solar cells.