Amorphous Indium Selenide Thin Films Prepared by RF Sputtering: Thickness-Induced Characteristics

Area of Science:

• Materials Science
• Thin Film Technology
• Renewable Energy

Background:

• Cadmium (Cd)-based buffer layers in CIGS solar cells pose environmental concerns.
• Development of Cd-free buffer layers is crucial for sustainable solar energy.
• Indium selenide (InSe) thin films are explored as potential alternatives.

Purpose of the Study:

• To investigate the effect of indium composition on optical and electrical properties of amorphous InSe thin films.
• To evaluate the suitability of these films as Cd-free buffer layers for CIGS solar cells.
• To establish a method for tuning InSe properties through controlled composition.

Main Methods:

• Amorphous indium selenide thin films were fabricated using RF magnetron sputtering.
• Film thickness was varied from 30 to 70 nm to control indium composition (94.56 to 49.72 at%).
• Optical transmittance, energy band gap (Eg), carrier concentration, and resistivity were measured.

Main Results:

• Optical transmittance increased from 87.63% to 96.03% with decreasing film thickness.
• Energy band gap (Eg) decreased from 3.048 to 2.875 eV.
• Excellent electrical properties were achieved: carrier concentration ≥10^15 cm⁻³ and resistivity ≤10^4 Ω·cm.
• Conductivity type was controllable by film-thickness-induced indium content.

Conclusions:

• Indium composition significantly influences the optical and electrical properties of amorphous InSe thin films.
• Tunable properties make these films viable Cd-free buffer layer candidates for CIGS solar cells.
• Film thickness offers a simple method to control composition and tailor properties for specific applications.