I am a Principal Scientist at the Energy Research Institute @ Nanyang Technological University, ERI@N.
My research interests range from hybrid halide perovskite materials' optical and electrical proprieties to their implementation in a variety of optoelectronic devices. Recently I mostly focused on the development of highly efficient single junctions solar cells and minimodules by thermal evaporation.
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.
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.
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)
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)