Interfacial alkali diffusion control in chalcopyrite thin-film solar cells.

Area of Science:

• Materials Science
• Photovoltaics
• Solid-State Chemistry

Background:

• Alkali elements like sodium (Na) are crucial for enhancing energy conversion efficiencies in chalcopyrite thin-film solar cells.
• Potassium (K) also shows beneficial effects on device performance, with unique properties distinct from Na.

Purpose of the Study:

• To demonstrate the controlled, selective diffusion of alkali elements potassium (K) and sodium (Na) into copper gallium selenide (CuGaSe2) thin films.
• To investigate the influence of growth parameters on alkali incorporation and concentration ratios.

Main Methods:

• Utilizing soda-lime glass substrates as a monolithic source of both K and Na.
• Analyzing the diffusion and incorporation of K and Na into CuGaSe2 films during growth.
• Controlling film structure and growth parameters to influence alkali concentration ratios.

Main Results:

• Selective diffusion of K and Na from the substrate into CuGaSe2 films was observed.
• Elemental K was incorporated into the Cu-deficient surface region of the CuGaSe2 film.
• Na was found to be ejected from the surface region, while K was incorporated.
• The [K]/[Na] concentration ratio in the CuGaSe2 surface region was controllable via growth parameters.

Conclusions:

• Selective alkali diffusion, particularly K incorporation, can be controlled in CuGaSe2 thin films.
• The findings provide new insights for developing advanced chalcopyrite-based solar materials.
• Optimizing alkali element incorporation is key for improving thin-film solar cell applications.