Ultra-low-cost coal-based carbon electrodes with seamless interfacial contact for effective sandwich-structured perovskite solar cells

The high cost of hole transporting materials (HTMs) and noble metallic electrodes limits the applications of perovskite solar cells (PSCs). Carbon materials, including carbon nanotube, graphene, and carbon paste, have been utilized for HTMs and noble-metal-free PSCs. Unlike other carbon materials, coal has extensive sources and lower price. A simple preparation process and an effective sandwich structure for the use of this material in PSCs were obtained by hot-pressing method. After the key parameters were adjusted, the power conversion efficiencies are 10.87% (0.3 cm 2 ) and 8.72% (1 cm 2 ). Therefore, devices with coal-based carbon electrodes have better stability than conventional devices. Our work proposes a promising future for the commercialization of low-cost and highly stable PSCs.