Reconsideration of the gallium nitride: Dual functionality as an electron transporter and transparent conductor for recyclable polymer solar cell substrate applications

Abstract Herein, we report the dual functionality of a single n-type gallium nitride (n-GaN) layer as an electron transporter and transparent conductor, which has applications in reusable organic solar cells. After silicon doping with an optimized electron concentration, thin-film layer of GaN showed exceptional electrical properties including charge carrier mobility of 161 cm2 V−1s−1, electrical conductivity of 1.4ⅹ106 S cm−1, and sheet resistance of 11.1 Ω cm−2. Organic solar cells based on n-GaN exhibited power conversion efficiency comparable to those based on a conventional ITO/ZnO bilayered cathode. Furthermore, the n-GaN substrates exhibited reusability; due to excellent chemical stability of n-GaN, the reconstructed organic solar cells maintained their initial performance after the substrates were recycled. We suggest a new type of reusable n-GaN cathode layer featuring an integrated electron transporting layer and transparent electrode.