Hole-Transport Material Engineering in Highly Durable Carbon-Based Perovskite Photovoltaic Devices

Despite the fast-developing momentum of perovskite solar cells (PSCs) toward flexible roll-to-roll solar energy harvesting panels, their long-term stability remains to be the challenging obstacle in terms of moisture, light sensitivity, and thermal stress. Compositional engineering including less usage of volatile methylammonium bromide (MABr) and incorporating more formamidinium iodide (FAI) promises more phase stability. In this work, an embedded carbon cloth in carbon paste is utilized as the back contact in PSCs (having optimized perovskite composition), resulting in a high power conversion efficiency (PCE) of 15.4%, and the as-fabricated devices retain 60% of the initial PCE after more than 180 h (at the experiment temperature of 85 degrees C and under 40% relative humidity). These results are from devices without any encapsulation or light soaking pre-treatments, whereas Au-based PSCs retain 45% of the initial PCE at the same conditions with rapid degradation. In addition, the long-term device stability results reveal that poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) is a more stable polymeric hole-transport material (HTM) at the 85 degrees C thermal stress than the copper thiocyanate (CuSCN) inorganic HTM for carbon-based devices. These results pave the way toward modifying additive-free and polymeric HTM for scalable carbon-based PSCs.

Automated summary

This study developed a high-efficiency and more stable perovskite solar cell by embedding carbon cloth in carbon paste as the back contact. Compared to Au-based solar cells, this type of cell showed better stability and maintained a high power conversion efficiency under the same conditions.