Perovskite Solar Cells — CityUHK's Clean-Energy Frontier in Chemistry and Materials

City University of Hong Kong (CityUHK) Integrated Information Database · 04 Research Module · Materials Science Deep-Dive Series For an overview and other landmark breakthroughs, see materials-and-engineering-research.md; for CityUHK's other flagship materials programme (high-entropy alloys), see High-Entropy Alloys and Advanced Metals.

A lab data point tells a commercialisation story: a perovskite solar cell, run continuously for over 1,000 hours at 65°C, still retains more than 90% of its efficiency. This is not an isolated laboratory figure — it is the phased answer delivered by a CityUHK chemistry team after tackling, back-to-back over three years, the twin obstacles of "efficiency" and "stability." It also marks another step closer to the day when this next-generation photovoltaic material genuinely leaves the lab and climbs onto a rooftop.

# 1. Why perovskite cells matter

Conventional silicon-based solar technology is mature, but its room for efficiency gains is narrowing and its manufacturing is fairly energy-intensive. Perovskite solar cells, by contrast, are seen as the "next generation" of photovoltaics because they promise high power conversion efficiency potential and low-cost solution-based fabrication. Yet two dragons stand guard at the gate:

1. Efficiency: how to push the light-to-electricity conversion rate higher;
2. Stability: perovskite materials are prone to degradation under moisture, heat, and light — the crux of commercial viability is "how long will it last."

The CityUHK team's research revolves around precisely these two challenges — and it proceeds layer by layer, in the order of "interface → thin film → fabrication process."

# 2. Representative achievements (all with public sources)

# 2.1 The ferrocene interface strategy: efficiency and stability in one go (2022)

April 2022^※, CityUHK chemists developed a strategy to boost both the efficiency and stability of perovskite solar cells. According to public reports, the team led by a CityUHK professor surnamed Zhu (Dr Zhu Zonglong), collaborating with Professor Long of Imperial College London, used ferrocenes as an interface between the light-absorbing layer and the electron-transport layer, achieving a breakthrough — this interfacial engineering simultaneously improved the device's performance and durability.

# 2.2 A non-volatile additive: inverted cell efficiency raised to roughly 24.8% (2023)

May 2023^※, the CityUHK team developed a multifunctional, non-volatile additive that boosts cell efficiency and stability by modulating the growth of the perovskite thin film. Reports indicated that inverted (p-i-n) perovskite solar cells based on the modified perovskite achieved a power conversion efficiency of approximately 24.8% — a notably high level. The research also drew attention from international photovoltaic media; one report mentioned Hong Kong researchers developing an inverted perovskite cell with 25.6% efficiency^※.

# 2.3 One-step solution coating: clearing the path to commercialisation (2023)

However high the efficiency, if the fabrication process is complex and hard to scale, a cell will struggle to reach the market. April 2023^※, CityUHK collaborated with the U.S. National Renewable Energy Laboratory (NREL) to co-develop a "one-step solution-coating" method that simplifies the manufacturing process and lowers the barrier to commercialisation. This work shifted the research focus from "lab efficiency" towards "how to actually manufacture perovskite cells at scale" — the critical leap from paper to product.

# 2.4 Three strands converge: the October 2023 Science paper

The threads above came together in a culminating synthesis in October 2023^※: the CityUHK Chemistry team led by Professor Zhu Zonglong designed a self-assembled monolayer (SAM), anchored onto the surface of nickel oxide nanoparticles as a hole-extraction layer, for use in inverted (p-i-n) structure perovskite cells. Test results showed that the improved devices retained more than 90% of their efficiency after running continuously for over 1,000 hours at roughly 65°C, with a power conversion efficiency reaching 25.6%. The corresponding paper, "Stabilized hole-selective layer for high-performance inverted p-i-n perovskite solar cells," was published in the top-tier journal Science, with collaborators led by Professor Li Zhong'an of Huazhong University of Science and Technology. In a sense, this paper is the consolidation of the preceding two years' experience in interfacial engineering and thin-film modulation — simultaneously pushing "efficiency" and "thermal stability," two indicators that often trade off against each other, to a level rarely seen before.

# 3. What characterises this research line

Stringing together the achievements above, several features of CityUHK's perovskite research come into view:

1. A full-chain "efficiency + stability + manufacturability" approach. From interfacial engineering (2.1) and thin-film control (2.2) to fabrication processes (2.3), and then the consolidating Science paper (2.4), CityUHK's research covers the complete chain of perovskite cells moving towards application, rather than chasing high efficiency numbers in the lab alone.
2. The intersection of chemistry and materials. This line spans the Department of Chemistry and materials science — perovskite research is essentially an intersection of "chemical synthesis + materials engineering + device physics," which fits squarely with CityUHK's cluster strength in materials science.
3. Intensive international collaboration. Partnerships with institutions such as Imperial College, the U.S. NREL, and Huazhong University of Science and Technology echo CityUHK's collaborative advantage as the "most international university in the world" (see 09-international/most-international-university.md).
4. Aligning with the clean energy megatrend. Perovskite photovoltaics directly serve the "energy transition / net-zero carbon" agenda, forming a complementary loop of "basic research—academic unit—campus practice" with the School of Energy and Environment (see 01-academics/school-of-energy-and-environment.md) and the net-zero carbon campus (see 05-campus/sustainability-and-net-zero.md).

A note on framing: Efficiency records for perovskite solar cells are broken frequently around the globe. Figures like "~24.8% / 25.6%" are reported values from specific studies at specific points in time, and a gap exists between lab efficiency and mass-production efficiency. When citing specific efficiency figures, always refer back to the original sources provided to verify their test conditions and timing.

# 4. Summary

• CityUHK has been making sustained breakthroughs in perovskite solar cells around the twin challenges of efficiency and stability: the ferrocene interface strategy (2022)^※, the non-volatile additive pushing inverted cell efficiency to ~24.8% (2023)^※, and the one-step solution-coating method co-developed with the U.S. NREL (2023)^※, ultimately culminating in the October 2023 Science paper^※ that simultaneously pushed both efficiency and thermal stability to new heights.
• This research line covers the full chain of "efficiency + stability + manufacturability," reflects the intersection of chemistry and materials and intensive international collaboration, and aligns with the broader clean energy megatrend.
• Efficiency figures are reported values from specific studies at specific points in time; citations must verify test conditions.