Sustainable Energy Materials and Device Group

Prof. Annalisa Bruno, Principal Investigator

Prof Annalisa Bruno

Principal Investigator

We are a research group exploring novel and precisely engineered optoelectronic materials based on hybrid snd sustainable soft semiconductors.

Research Highlights

Ultrathin Fully Vacuum-Processed Perovskite Solar Cells with Absorbers Down to 10 nm

Luke R. W. White et al., ACS Energy Letters (2026)

This study demonstrates that fully vacuum-processed perovskite solar cells can retain high optoelectronic quality even when the MAPbI₃ absorber thickness is reduced to only 10 nm. By precisely controlling thermal co-evaporation, the authors obtain continuous and uniform ultrathin films across a broad thickness range using the same deposition conditions, with thickness adjusted only through deposition time. The ultrathin devices preserve open-circuit voltage and fill factor values comparable to bulk absorbers, indicating low trap density, limited interfacial recombination, and high film uniformity, while the principal efficiency loss arises from reduced light absorption. Record efficiencies of 6.9%, 10.9%, and 11.8% are achieved for 10, 30, and 60 nm absorbers, respectively. Semitransparent devices further reach an average visible transparency of up to 65%, with a practical light-utilization efficiency of 3.13% for the 60 nm device and a potential value of 5.15% for the 30 nm absorber, establishing thermally evaporated ultrathin perovskites as a scalable platform for transparent and building-integrated photovoltaics.

Overcoming the Voltage Deficit in Hybrid-Processed Wide-Bandgap Perovskite Solar Cell

Li Ling et al., Advanced Energy Materials (2026)

This study demonstrates that the large open-circuit-voltage deficit commonly observed in hybrid-processed wide-bandgap perovskite solar cells is not intrinsic to the deposition method, but originates from incomplete diffusion-limited conversion and severe non-radiative recombination at the charge-transport interfaces. By introducing methylammonium chloride to regulate crystallization kinetics and improve vertical halide homogeneity, together with bifacial interfacial engineering using PDAI₂/4F-PEAI and NiOₓ/Ph-4PACz, the work simultaneously enhances bulk film quality, suppresses interfacial trap-assisted recombination, and optimizes energy-level alignment. The optimized 1.7 eV devices achieve a record open-circuit voltage of 1.269 V, approaching 90% of the radiative limit, together with a power conversion efficiency of 21%. The strategy also maintains strong performance under indoor illumination and in 1 cm² devices, establishing hybrid deposition as a scalable route toward high-efficiency wide-bandgap top cells for perovskite/silicon tandem photovoltaics.

Low-threshold superfluorescence in quasi-2D metal halide perovskite thin films

Yue Tang et al., Advanced Materials (2025)

This study reveals cooperative quantum emission in quasi-2D perovskite thin films with one of the lowest superfluorescence thresholds reported in perovskites. By mapping the transition between spontaneous emission, amplified spontaneous emission, and superfluorescence across temperature and excitation fluence, the work clarifies how phase dynamics govern light emission in these materials. The findings strengthen the case for metal halide perovskites as a versatile platform for quantum photonics and coherent light sources operating at elevated temperatures.

Stable infrared Yb-doped perovskite quantum cutters engineered by machine learning

Yao Jing et al., Advanced Materials (2024)

This work combines ligand engineering, phosphine-oxide-assisted synthesis, and machine learning to create highly stable Yb-doped perovskite quantum cutters with near-infrared photoluminescence quantum yield above 190%. The optimized nanocrystals retain their high performance under prolonged storage, continuous UV illumination, and thermal stress, addressing one of the major bottlenecks in this class of materials. Beyond the impressive quantum-cutting efficiency, the study showcases how data-driven materials optimization can accelerate the discovery of robust perovskite emitters for photonics and spectral-conversion applications.

Accelerated MAPbI3 co-evaporation for scalable perovskite manufacturing

Herlina Arianita Dewi et al., ACS Energy Letters (2024)

Vacuum deposition is a promising industrial route for perovskite photovoltaics, but long deposition times remain a practical bottleneck. In this work, the MAPbI3 co-evaporation process was accelerated six-fold, reducing the deposition time from 150 minutes to just 25 minutes without compromising film quality or device performance. The results highlight a major productivity gain for vapor-deposited perovskites and reinforce thermal co-evaporation as a serious pathway toward scalable, high-throughput device fabrication.

Co-evaporated p-i-n perovskite solar cells with sputtered NiOx hole transport layer

Enkhtur Erdenebileg et al., Materials Today Chemistry (2023)

This study reports the first co-evaporated p-i-n perovskite solar cells using sputtered NiOx as the hole transport layer, bringing together two scalable and solvent-free processes in a single device architecture. By tuning the sputtering conditions and interface properties, the work achieved efficient MAPbI3 solar cells while also demonstrating compatibility with low-temperature processing. The paper establishes an important platform for robust, industry-compatible perovskite photovoltaics and underlines the potential of evaporated perovskites for large-area manufacturing.

10/21

Recent progress of vapor-deposited perovskite solar cells (PSCs) has proved the feasibility of this deposition method in achieving promising photovoltaic devices. For the first time, it is probed the versatility of the co-evaporation process in creating perovskite layers customizable for different device architectures. A gradient of composition is created within the perovskite films by tuning the background chamber pressure during the growth process. This method leads to co-evaporated MAPbI3 film with graded Fermi levels across the thickness. Here it is proved that this growth process is beneficial for p-i-n PSCs as it guarantee a favorable energy alignment at the charge selective interfaces. Co-evaporated p-i-n PSCs, with different hole transporting layers, consistently achieve power conversion efficiency (PCE) over 20% with a champion value of 20.6%, one of the highest reported to date. The scaled-up p-i-n PSCs, with active areas of 1 and 1.96 cm2, achieved the record PCEs of 19.1% and 17.2%, respectively, while the flexible PSCs reached a PCE of 19.3%. Unencapsulated PSCs demonstrate remarkable long-term stability, retaining ≈90% of their initial PCE when stored in ambient for 1000 h.

04/21

Thermal stability is a critical criterion for assessing the long-term stability of perovskite solar cells (PSCs). We have shown that un-encapsulated co-evaporated MAPbI3 PSCs have remarkable thermal stability even in an n-i-p structure that employs Spiro-OMeTAD. The PSCs maintain over ≈80% of their initial power conversion efficiency (PCE) after 3600 h at 85 °C.

This excellent thermal stability is related to the perovskite growth process leading to a compact and almost strain-stress-free film. Un-encapsulated PSCs with the same architecture, but incorporating solution-processed perovskite, show a complete PCE degradation after 500 h under the same thermal aging condition.

These results highlight that the control of the perovskite growth process can substantially enhance the PSCs thermal stability, besides the chemical composition. The TE_MAPbI3 impressive long-term thermal stability features the potential for field-operating conditions.

04/20

Although small-area perovskite solar cells (PSCs) have reached remarkable power conversion efficiencies (PCEs), their scalability still represents one of the major limits toward their industrialization. For the first time, we prove that PSCs fabricated by thermal co-evaporation show excellent scalability.

Indeed, our strategy based on material and device engineering allowed us to achieve the PCEs as high as 20.28% and 19.0% for 0.1 and 1 cm2 PSCs and the record PCE value of 18.13% for a 21 cm2 mini-module.

J Li, H.Wang, XY Chin, HA Dewi, K Vergeer, T W Goh, J H Lew, K P Loh, C Soci, T C Sum, H Bolink, N Mathews*, S. Mhaisalkar*, A Bruno* Highly Efficient Thermally Co-evaporated Perovskite Solar Cells and Mini-modules, 1. 4 (5), 1035, (2020)

01/20 Semitransparent perovskite solar cells (SCs) and their potential integration with silicon SCs in tandem configurations attract significantly increasing interest in the photovoltaics community. In addition to being highly spectrally complementary, these perovskite and silicon SCs have very different optimal‐performing sizes and consequently ideal measurement schemes for their integration in four‐terminal (4T) tandem configurations need to be investigated in detail. Herein, the effect of different active areas on both perovskite and silicon SCs on their photovoltaic performances is investigated. Furthermore, the commonly used filtering 4T tandem measurement scheme (named as filtered) is systematically compared with the size‐matching scheme (named as masked) demonstrating that when using the same top semitransparent perovskite and bottom silicon SCs in different measurements schemes, the total 4T tandem power conversion efficiency (PCE) can differ by more than 1%. The concepts presented here highlight the importance of optimal measurement schemes to assess 4T tandem PCE and rationalize the effect of compromise between the subcells size matching and the identification of the maximum PCE potential.

HA Dewi, H Wang, J Li, M Thway, R Sridharan, F Lin, AG Aberle N. Mathews, S Mhaisalkar, A Bruno*, Four‐Terminal Perovskite on Silicon Tandem SolarCells Optimal Measurements Schemes, Energy Technology (2020)

12/2019

Tandem solar cells (SCs) based on perovskite and silicon represent an exciting possibility for a breakthrough in photovoltaics, enhancing solar cell power conversion efficiency (PCE) beyond the single junction limit while keeping the production cost low. A critical aspect to push the tandem PCE close to their theoretical limit is the development of high-performing semi-transparent perovskite top-cells which also allow suitable near-infrared transmission. Here, we have developed highly efficient semi-transparent perovskite solar cells (PSCs) based on both mesoporous and planar architectures, employing Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3 and FA0.87Cs0.13PbI2Br perovskites with bandgap of 1.58 eV and 1.72 eV respectively which achieved PCEs well above 17% and 14% by detailed control of the deposition methods, thickness and optical transparency of the interlayers and the semi-transparent electrode. By combining our champion 1.58 eV PSCs (PCE of 17.7%) with an industrial-relevant low cost n-type Si SCs, a 4 terminals (4T) tandem efficiency of 25.5% has been achieved. Moreover for the first time, 4T tandem SCs performances have been measured in the low light intensity regime achieving a PCE of 26.6%, corresponding to a revealing a relative improvement above 9% compared to standard 1 sun illumination condition. These results are very promising for their implementations under field-operating conditions.

1. HA Dewi, H Wang, J Li, M Thway, R Sridharan, R Stangl, F Lin, AG Aberle N. Mathews, A Bruno*, S Mhaisalkar. HighlyEfficient Semi-Transparent Perovskite Solar Cells for Four TerminalPerovskite-Silicon Tandems, ACS applied materials & interfaces (2019)

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