A conductive adhesive ink for carbon-laminated perovskite solar cells with enhanced stability and high efficiency

Utilizing carbon-laminated electrodes on perovskite solar cells (PSCs) benefits from simple fabrication process and low-cost material, in addition to enhanced stability. In this method, carbon foils are laminated on the underlying hole transport layer (HTL), so the HTL/carbon electrode interface is of the utmost importance in achieving high-performance devices. Here, we develop a conductive adhesive ink, consisting of poly methyl methacrylate (PMMA), highly conductive carbon black (HCCB), and CuInS2 (CIS) nanoparticles, as the interfacial adhesive layer between the underlying CIS HTL and the top carbon electrode. Utilizing carbon foil, wetted by the proposed optimized adhesive ink layer, allows simply pressing the top carbon electrode on CIS HTL. The prepared optimized carbon-laminated PSCs lead to a maximum power conversion efficiency (PCE) of 17.2 % for the best PSC, as compared with the maximum PCE of 18.2 % for the best sample of conventional Au-based PSC. Furthermore, the average PCE of the fabricated optimized carbon-laminated PSCs has kept almost 92 % of the average maximum PCE value after about 54 days, which is a significant enhancement in device stability in comparison with conventional Au-based PSCs, which have degraded to 75 % of their maximum PCE. The proposed carbon lamination method seems very promising for overcoming the stability challenge of PSCs, and the realization of low-cost, large-area, highly stable, and efficient solar cells.