High figure of merit p-type transparent conducting thin film based on solution processed CuS-ZnS nanocomposite

Until now only n-type transparent conducting films (TCFs) have accomplished sufficient maturity while p-type TCFs are still in infancy which limits the success of all-transparent electronics. Considerable endeavors are made till date for development of new p-type TCFs with limited success. Here, we report a highly transparent and conducting p-type thin films (∼60 nm) based on CuS-ZnS nanocomposite deposited by simple chemical bath deposition method at ∼80 °C on glass substrates using different x values (0.1, 0.35, 0.6, 0.8) where x = Cu (mol %)/(Cu+Zn) (mol%). Grazing incidence X-ray diffractometry, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and atomic force microscopy are used to evaluate the structural and microstructural characteristics of the films. The existence of ZnS phase is seen only for x ≤ 0.6 due to a preferential deposition of CuS which helps to retain a significant visible light transparency for x = 0.6 with a small drop in the conductivity value as compared to CuS. Thus the film with x = 0.6 is found to have the optimum electrical properties with resistivity, hole concentration, and mobility values of 1.03×10⁻³ Ω-cm, 4.16 × 10²² cm⁻³, and 0.15 cm²/Vs respectively as well as an optical transmission value of 83% at 550 nm. An unprecedented figure of merit value of 9.2 × 10⁻⁴ Ω⁻¹ is obtained for the optimized film which is not reported till date to our knowledge. A p-n heterojunction is fabricated using the optimized film on n-GaN which shows a rectification ratio of 3.06 × 10⁴ at 2 V indicating a great potential as p-type TCF for flexible transparent electronics.