Innovative Interface Materials for Perovskite Photovoltaics

This is a sponsored article by Nano-C

Authors: H. Richter, D. Bischoff, E. A. Jackson, R. M. Carty, H. Ghiassi, T. A. Lada, M. J. Ricci, M. Kollosche and P. C. Brookes. email: hrichter@nano-c.com

New global energy demand is being driven by vehicle electrification, datacenters, and AI computing. According to IEEE, over 70% of all newly installed energy generation capacity in 2024 came from photovoltaics. Traditional solar cells based on silicon and cadmium telluride were key to this rapid adoption, however, these universal technologies are reaching their practical conversion efficiency. The primary solution to offer a step change in efficiency while promising to reduce the levelized cost of energy (LCOE) comes from the use of perovskite-based solar cells in tandem with traditional technologies. In addition, the implementation of organic thin film PV as well as flexible perovskite PV enables installations and integrations not feasible with traditional glass-based architectures.

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In order to meet increasing global energy demand while also seeking to achieve reductions in global CO₂ emissions, a new generation of organic and perovskite photovoltaics are needed to: a) enhance the performance of existing, e.g., silicon solar PV and b) allow for the energy- and cost-efficient manufacturing of photovoltaic devices on light-weight flexible substrates. While the emerging silicon-tandem perovskite architectures can result in the rapid deployment of PV modules with significantly higher performance by leveraging existing manufacturing and installation infrastructure, single- or multijunction OPV and perovskite photovoltaics have the potential to significantly extend the range of use cases including building integrated applications (BIPV) for indoor, semi-transparent uses (e.g., for windows) as well as roof top where weight limitations are a factor.

The global implementation of organic and perovskite PV requires all key materials to be economically viable at industrial scale. Nano-C’s mission has been to develop and manufacture materials critical for the success of these next generation solar technologies. Spun-off from the Massachusetts Institute of Technology (MIT) in 2001, initially with the focus to scale-up patented technology to manufacture fullerenes, particularly C60 and C70 used in solar applications. A reactor used for the production of fullerenes at Nano-C is shown in Fig. 1.
 

Fig.1 Fullerene reactor at Nano-C.

Realizing the potential of using fullerene-based materials as electron acceptor material in the active layer of organic photovoltaic (OPV) devices, Nano-C  developed a large portfolio of proprietary fullerene derivatives enabling increased performance, particularly in terms of stability. Current performance of light-soaking stability under 1 SUN (at 55 – 65 °C) of a small-scale device fabricated at Nano-C is shown in Fig. 2. Reaching power conversion efficiencies of > 14% based on fully solution-processed active and inter-layers material.  This device was fabricated in an industrially relevant inverted architecture using a proprietary fullerene derivative combined with a commercially available polymer as well as a scalable non-fullerene acceptor (NFA).

Fig.2 Light soaking (at 55 to 65 °C) of OPV device using proprietary fullerene derivative from Nano-C.

In addition to its activities regarding active and inter-layer materials, Nano-C is developing coat-ready formulations based on silver nanowires as well as hybrid systems that also contain single-walled carbon nanotubes targeting transparent top and bottom electrodes.

Leveraging the foundational product development in OPV materials, including NFAs, has been critical to supplying current and future perovskite PV architectures. Industrial-scale supply of standard C60 and sublimed C60 have been optimized for electronic applications, particularly vapor-deposition of electron transport layers.  More importantly, as high volume PV applications start to utilize solution processing of their interface layers, a significant library of products exists to optimize performance based on particular application requirements and production equipment.

Based on market needs, Nano-C’s active development roadmap also includes next generation electron transport (ETM) and hole transport (HTM) materials. Some examples of interface materials available from Nano-C are shown in Fig. 3. These materials are available as mono- and bis-adduct that allows for the improvement of band alignment (and minimizing non-radiative recombination) depending on the bandgap of the perovskite material used. Increased performance, also in terms of thermal, light-soaking and mechanical stability is targeted.

Fig. 3 Examples of interlayer materials available from Nano-C (from left to right): C60-C6-PA, CPPA, C60-malonate-2NH3l, 4-phosphonic acid-triphenylamine.

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 In this context, a range of fullerene derivatives bearing carboxylic and, particularly, phosphonic acid have been synthesized and are available to cell developers. Having the capability to form self-assembled monolayers (SAMs), e.g., on SnO2, particularly bis-versions of such molecules, offers the ability to stabilize the perovskite phase. Ammonium bearing fullerene derivatives, such as C60-malonate-2NH3l, target interface passivation, particularly, in p-i-n architectures. Recently, a tri-phenylamine bearing phosphonic acid has been synthesized and is available for evaluation as HTM.

Further, Nano-C offers coat-ready formulations of carbonaceous nanomaterials, particularly but not only, single-walled carbon nanotubes to be used as opaque top-electrode for single-junction Perovskite devices.

Materials like fullerenes, NFAs, nanocarbons, and silver nanowires all promise to play an important role in the large-scale adoption of next generation solar cells.   The need for materials with unique properties, such as high electron mobility, chemical and thermal stability when accepting electrons, and ability to form thin, defect-free semiconductor films, is essential for high-performance devices.

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Visit our booth at the Perovskite Connect event co-located with the Future of Electronics RESHAPED on 22-23 October 2025 in Berlin. Contact us for your special discount coupon to attend!