Perovskite solar cells (PSCs) have achieved remarkable progress in power conversion efficiency, while further advances in device stability, scalable fabrication, and material sustainability are required for their practical implementation. In this invited presentation, we report our recent efforts to develop carbon-based electrode and electron-transport materials for next-generation PSCs, with particular emphasis on single-walled carbon nanotube (SWCNT) transparent electrodes and vacuum-depositable fullerene derivatives.

SWCNT thin films are attractive alternatives to conventional transparent conductive oxides because of their high optical transparency, mechanical flexibility, chemical stability, and compatibility with solution processing. We have investigated SWCNT films as transparent top electrodes for PSCs and demonstrated devices with a power conversion efficiency exceeding 18%. Importantly, the SWCNT electrodes also provide opportunities for improving long-term device durability and for developing lightweight and flexible photovoltaic architectures.

In parallel, we have developed a series of thermally evaporable fullerene derivatives as electron-transport materials for inverted PSCs. Molecular modification of C60 enables systematic control of electronic properties, interfacial interactions, and device stability while retaining sufficient thermal stability for vacuum deposition. Indano[60]fullerene-based derivatives, including ketone- and trifluoromethyl-containing structures, have afforded photovoltaic performance exceeding that of conventional C60 electron-transport layers, with power conversion efficiencies above 25%. Further molecular engineering, including position of substituents and improvement of thermal stability during evaporation, provides a route toward robust fullerene derivative-based electron-transport layers compatible with dry processing.

These two approaches illustrate complementary strategies for controlling both sides of the perovskite device architecture: carbon nanotubes networks as transparent charge-collecting electrodes and molecularly engineered fullerenes derivatives as vacuum-processable electron-transport layers. Their combination may provide new opportunities for reducing reliance on conventional transparent conductive oxides, improving device durability, and establishing scalable and versatile fabrication processes for future perovskite photovoltaics.