Efficient CdTe Solar Cells with an Al Back Electrode Enabled by a Mo/Cr Interfacial Modification Layer

Although metallic aluminum (Al) is an attractive back electrode material for cadmium telluride (CdTe) solar cells due to its low cost and suitability for large-area deposition, its low work function has hindered widespread application. To overcome this challenge, we designed and implemented a molybdenum-chromium (Mo/Cr) interfacial modification layer. A comprehensive comparative analysis was carried out to evaluate the electrical characteristics, interfacial transport properties, and device performance of the Al, Mo/Cr-modified Al and Au electrodes. The results reveal that the Mo/Cr interfacial modification layer effectively improves Al-electrode interfacial transport properties and conductivity and also blocks the diffusion of Al atoms. The optimized device with a Mo/Cr-modified Al electrode achieved a champion efficiency of 15.68%, closely approaching 15.88% of the expensive, high-work-function gold (Au) reference and significantly surpassing 13.83% of the Al electrode. Furthermore, it exhibited excellent mechanical adhesion and wear resistance, with a critical load of 0.62 mN, substantially higher than the 0.45 and 0.42 mN for the Al and Au electrodes, respectively. This electrode architecture offers a low-cost, highly durable, and high-performance alternative to noble-metal contacts, showing great potential for facilitating the large-scale commercialization of thin-film photovoltaic technology.