Sulfur-Doped ZnO as Cathode Interlayer for Efficient Inverted Organic Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Device Physics

Background:

• Bulk heterojunction (BHJ) organic solar cells (OSCs) offer cost-effective, lightweight, and flexible energy solutions.
• Optimizing interfacial layers is critical for enhancing power conversion efficiency (PCE) and stability in OSCs.
• Zinc oxide (ZnO) is a common electron extraction layer (EEL) in inverted OSCs, but surface defects limit its performance.

Purpose of the Study:

• To investigate sulfur doping of ZnO as a method to improve conductivity and optoelectronic properties.
• To enhance interfacial electron transfer, exciton dissociation, and reduce non-radiative recombination in OSCs.
• To optimize the annealing temperature for sulfur treatment of ZnO films.

Main Methods:

• Sulfur treatment of ZnO films under various annealing temperatures.
• Fabrication and characterization of inverted OSCs using pristine and sulfur-doped ZnO (S-ZnO) EELs.
• Analysis of device performance (PCE, Jsc, FF) and material properties (conductivity, crystallite size, electron transport).

Main Results:

• Optimal sulfur treatment achieved at 250 °C annealing temperature.
• S-ZnO based OSCs showed a significant PCE increase from 2.11% to 3.14%.
• Improved short-circuit current density (Jsc) and fill factor (FF) were observed, attributed to enhanced electron extraction and exciton dissociation.

Conclusions:

• Sulfur doping is a facile and effective method to enhance ZnO conductivity and performance as an EEL.
• Optimized S-ZnO improves interfacial charge dynamics, leading to higher PCE in inverted OSCs.
• This approach offers a straightforward strategy for boosting the performance of organic solar cell technology.