Improvement of AgGaTe ₂ Solar Cell Performance by Improving the Quality of AgGaTe ₂ Thin Film

Environmentally friendly solar cells using AgGaTe 2 as the light‐absorbing layer has been prepared using the close‐space sublimation (CSS) method. In Cu(In, Ga)Se 2 solar cells, which has a similar structure to AgGaTe 2 , results exceeding 20% efficiency have been reported by using Ga‐rich CIGS thin films. Therefore, in this study, AgGaTe 2 thin films were adjusted to Ga‐rich layers without deteriorating the quality of the solar cell structure. In previous work, extending the sublimation CSS time from 3 to 45 min enabled the fabrication of Ga‐rich AgGaTe 2 thin films and improved conversion efficiency. However, this also increased the number and size of holes in the films, deteriorating the interface quality. To resolve this issue and fabricate Ga‐rich AgGaTe 2 thin films with improved quality, two approaches were considered. First, the CSS sublimation time was decreased to 15 min to suppress excessive heating. Second, the amount of source material was increased to ensure sufficient Ga sublimation even with a shorter sublimation time. Increasing the source material alone did not result in a Ga‐rich film; instead, the film remained nearly stoichiometric. However, reducing the sublimation time from 45 to 15 min improved the film quality, increasing the conversion efficiency from 1.21% to 2.48%.