Solution-processed pH-neutral conjugated polyelectrolyte improves interfacial contact in organic solar cells.

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• The acidic poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole-transporting layer (HTL) causes interfacial protonation in organic solar cells.
• This protonation limits device performance, particularly in cells utilizing basic pyridylthiadiazole units.

Purpose of the Study:

• To investigate a pH-neutral conjugated polyelectrolyte (CPE-K) as an alternative HTL.
• To enhance the performance of organic solar cells by eliminating interfacial protonation and energy barriers.

Main Methods:

• Fabrication of p-DTS(PTTh2)2:PC71BM organic solar cells using CPE-K as the HTL.
• Comparison of device performance metrics (PCE, V(bi), R(s), charge extraction) with those using PEDOT:PSS HTL.

Main Results:

• A 60% enhancement in power conversion efficiency (PCE) was achieved with the CPE-K HTL.
• The CPE-K HTL led to increased open-circuit voltage (V(bi)) and reduced series resistance (R(s)).
• Improved charge extraction and elimination of interfacial protonation were observed compared to PEDOT:PSS.

Conclusions:

• pH-neutral CPE-K is a superior HTL for organic solar cells compared to acidic PEDOT:PSS.
• Eliminating interfacial protonation is crucial for enhancing organic solar cell efficiency.
• CPE-K offers a promising pathway for developing high-performance organic photovoltaic devices.