Colloidal solution-processed CuInSe2 solar cells with significantly improved efficiency up to 9% by morphological...

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Copper Indium Selenide (CuInSe2 or CISe) is a promising material for low-band-gap solar cells.
• Colloidal solution deposition offers a cost-effective method for fabricating CISe precursor films.
• Achieving high photovoltaic performance in CISe solar cells requires optimizing precursor film density and microstructure.

Purpose of the Study:

• To investigate the impact of precursor film green density on the photovoltaic performance of CISe solar cells.
• To explore the use of cold-isostatic pressing (CIP) to enhance green density and microstructural properties.
• To correlate microstructural improvements with enhanced device performance metrics.

Main Methods:

• Fabrication of Cu-In nanoparticle precursor films using colloidal solution deposition.
• Application of cold-isostatic pressing (CIP) to increase precursor film green density by approximately 20%.
• Sintering of precursor films to form CISe absorber layers and subsequent device fabrication and characterization.

Main Results:

• CIP treatment significantly improved microstructural features: lower porosity, uniform surface morphology, and a thinner MoSe2 layer.
• CISe solar cells fabricated with CIP-treated films showed enhanced open-circuit voltage (V(OC)) from 0.265 to 0.413 V and fill factor (FF) from 0.34 to 0.55.
• The average power conversion efficiency increased nearly threefold, from 3.0% to 8.2%, with a highest recorded efficiency of 9.02%.

Conclusions:

• Enhanced green density via CIP is a critical factor for improving CISe solar cell performance.
• Microstructural improvements, including reduced porosity and defects, lead to suppressed recombination and better device metrics.
• CIP treatment effectively reduces interface recombination, contributing to higher V(OC) and FF in CISe solar cells.