How Dr. Pisist Kumnorkaew and his collaborators are advancing perovskite photovoltaics through nanomaterial engineering, controlled solar simulation, and industry-focused scale-up
“I group people from academia and private companies together, and we try to set up proposals to the government to build something like a pilot plant, or larger equipment, for perovskite solar-cell scale-up in the near future.”
— Dr. Pisist Kumnorkaew, National Nanotechnology Center, Thailand
Solar-cell performance is often summarized by a single efficiency value. Reaching that value, however, requires control over a much larger system: material composition, thin-film morphology, interfacial charge transfer, device fabrication, environmental stability, and the light source used during characterization.
At the National Nanotechnology Center, or NANOTEC, in Thailand, Dr. Pisist Kumnorkaew works across this full development pathway. His research centres on perovskite solar cells, together with functional nanocoatings, industrial materials, and the scale-up of nanotechnology from laboratory formulations to practical systems.
His group’s work illustrates how perovskite photovoltaics can progress from small experimental cells to large-area minimodules and, eventually, low-power devices operating under real-world conditions.
Table of Contents
- Building a Bridge Between Materials Research and Industry
- The Challenge of Reliable Photovoltaic Characterization
- Passivating the Perovskite Surface with a Metal–Organic Framework
- Developing Stable and Scalable Perovskite Solar Cells
- From Small Cells to Indoor IoT Power
- Expanding into Nanocoatings and Materials Testing
- The Path Toward Pilot-Scale Manufacturing
Building a Bridge Between Materials Research and Industry
Dr. Kumnorkaew received his PhD in chemical engineering from Lehigh University in Pennsylvania, where he studied the flow, self-assembly, and thin-film behaviour of nanoparticles and microparticles. He remained at Lehigh for postdoctoral research focused on dye-sensitized solar cells before returning to Thailand through a government scholarship program.
Since returning, he has spent approximately 15 years conducting research at NANOTEC, part of Thailand’s National Science and Technology Development Agency (NSTDA). His early work continued in dye-sensitized and polymer solar cells. As perovskite photovoltaics emerged, the group redirected its photovoltaic effort to this material system, combining its experience in semiconductor devices, polymers, nanoparticles, and thin-film processing. Perovskite solar cells have been the group’s principal photovoltaic focus since.
Today, Dr. Kumnorkaew is a group director overseeing four research teams. His work sits at the intersection of fundamental materials science and industrial development. In addition to publishing research, he collaborates with universities, private companies, and government organizations to move promising technologies toward pilot-scale production.
His laboratory reflects this multidisciplinary role. It combines a cleanroom, glovebox, thermal evaporator, photovoltaic measurement equipment, nanoparticle synthesis facilities, and polymer formulation capabilities. The team also maintains an outdoor rooftop test site, allowing laboratory measurements to be compared with exposure to Thailand’s hot and humid climate.
The Challenge of Reliable Photovoltaic Characterization
For photovoltaic researchers, improving a material is only part of the challenge. They must also demonstrate that the resulting device performs consistently under known and repeatable illumination.
Earlier in his career, Dr. Kumnorkaew was forced to use xenon-based solar simulators. Although these systems could reproduce solar-like illumination, his team encountered changes in light intensity during use and difficulties associated with lamp alignment. These experiences motivated the group to investigate LED-based systems.
The laboratory acquired a G2V Pico LED solar simulator in approximately 2021. After using the Pico for small-area device measurements, a collaborating group added a Sunbrick to support larger samples. According to Dr. Kumnorkaew, the Sunbrick became the laboratory’s main solar simulator. The team regularly checks its irradiance with a light sensor and reported stable operation over several years of use.
“Once I buy a piece of equipment, set it up, and find that it works well, my colleagues usually follow me.”
The Pico is integrated directly into NANOTEC’s perovskite research environment. The group operates a dedicated cleanroom containing a glovebox, thermal evaporator, and the Pico measurement system. Approximately half of the laboratory’s activity takes place in this cleanroom and is focused on perovskite solar-cell research. The room is maintained at approximately 18 °C, giving the researchers a controlled environment for device fabrication and subsequent photovoltaic characterization.
An important part of the group’s measurement procedure is that light exposure and electrical characterization are treated as two separate steps. Before measuring a perovskite device, the researchers first perform a short light-soaking step. For this purpose, they continue to use xenon lamps already available in the laboratory. The samples are typically exposed for approximately three to five minutes before the electrical measurement begins. The xenon systems are therefore no longer the group’s primary measurement source; instead, they are mainly used for this pre-measurement exposure step.
After light soaking, the sample is moved to the Pico for photovoltaic characterization under LED illumination. This part of the process is considerably faster. A typical substrate is roughly one inch by one inch and contains eight individual solar cells, and Dr. Kumnorkaew reported that the team can measure the complete set in approximately one minute.
For a research program that routinely compares different materials, interfaces, and fabrication conditions, this workflow provides a practical separation between device conditioning and device measurement. The xenon source is used to prepare the perovskite device before measurement, while the Pico provides the controlled illumination used to collect the electrical performance data. This allows the researchers to move rapidly between samples while maintaining consistent test conditions for comparisons between different device formulations.
The laboratory also extends its testing beyond controlled indoor measurements. NANOTEC maintains a rooftop test site where solar cells and other materials can be exposed to natural sunlight and Thailand’s hot and humid climate. Samples can therefore progress from controlled characterization under a solar simulator to outdoor testing under real environmental conditions.
Together, these different stages create a broader testing workflow: fabrication in the cleanroom, short light soaking, controlled LED-based electrical characterization, and finally outdoor validation. For Dr. Kumnorkaew’s team, reliable solar simulation is therefore not an isolated measurement step, but one part of a larger process for determining whether improvements observed at the material level translate into repeatable photovoltaic performance.
Passivating the Perovskite Surface with a Metal–Organic Framework
The perovskite surface is where much of the group’s interface engineering is concentrated. Even in a well-formed film, the top surface carries unreacted lead iodide and unsatisfied bonds that act as non-radiative recombination centres. These cost open-circuit voltage, limit charge extraction, and open the path along which the device later degrades, so treating that surface is as consequential as improving the absorber itself.
In a study with collaborators at Chiang Mai University, King Mongkut’s University of Technology Thonburi and Mahidol University, the team addressed this with cuprous oxide nanoparticles grown inside a MIL-53(Al) metal–organic framework — abbreviated CuM. Cu2O is an excellent hole conductor but difficult to apply to a finished perovskite film, because the solvents that dissolve it attack the layer underneath.
Hosting 8–10 nm Cu2O particles inside an aluminium-terephthalate framework solves that. The composite disperses in 2-butanol and deposits by ordinary spin coating, while the framework’s aromatic linkers interact with lead species at the perovskite surface. The terephthalate linker itself was recovered from waste PET by alkaline hydrolysis, keeping the passivation route low-cost and environmentally benign.
The CuM dispersion was spin-coated onto the finished perovskite film and annealed briefly at 100 °C, then capped with Spiro-OMeTAD in a planar n–i–p stack: ITO / SnO2 / perovskite / CuM / Spiro-OMeTAD / gold. Five loadings were compared, from none up to 0.1 mg/mL, so the effect of the modifier could be separated from the effect of simply adding a layer. Current–voltage characteristics were measured with a Keithley 2450 source meter under simulated AM1.5G illumination at 100 mW/cm² from the G2V Pico LED solar simulator, over an active area of 0.09 cm², with sixteen devices per condition.
The best performance came at 0.075 mg/mL: a power-conversion efficiency of 20.25%, with open-circuit voltage rising from 1.08 to 1.11 V, short-circuit current density from 22.91 to 23.89 mA/cm², and fill factor from 75.53% to 76.51%, against 18.68% for the untreated control. At 0.1 mg/mL efficiency fell back to 19.71% — the same lesson the group meets repeatedly, that there is an optimum loading rather than a monotonic trend. Forward and reverse scans showed negligible hysteresis throughout.
Supporting measurements explained where the gain came from. X-ray diffraction showed a reduced lead-iodide contribution at the surface, and X-ray photoelectron spectroscopy showed a shift in the Pb 4f binding energy consistent with the framework’s terephthalate ligands interacting with surface lead species. Carrier lifetime in the bare film rose from 8.30 to 11.45 ns, while in the full stack with the hole-transport layer it fell from 0.89 to 0.15 ns — slower recombination but faster extraction, exactly the combination a passivation layer should produce.
The durability result mattered as much as the efficiency. Held unencapsulated in the dark at 40–60% ambient relative humidity under the ISOS-D-1 protocol, the treated device kept 96.56% of its initial efficiency after 1,000 hours, against 78.66% for the untreated control; under thermal storage at 65 °C in nitrogen, retention was 93% against 77%. As in the group’s other work, that conclusion rests on comparing many devices under illumination that does not drift between them — which is why the repeatability of the light source, and not only its peak accuracy, is what the measurement depends on.
Developing Stable and Scalable Perovskite Solar Cells
Perovskite solar cells have reached high laboratory efficiencies, but performance alone does not guarantee commercial viability. Long-term stability, resistance to thermal processing, reproducibility, and the ability to fabricate larger modules remain major development challenges.
One critical component is the hole-transport layer, or HTL. The HTL must efficiently extract positive charge carriers from the perovskite while minimizing recombination and maintaining a stable interface over time.
Combining an Organic Polymer with Inorganic Nanoparticles
Dr. Kumnorkaew and an extensive group of collaborators investigated a hybrid hole-transport material formed by incorporating nickel oxide nanoparticles into poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], commonly known as PTAA.
PTAA is attractive because of its processability, favourable energy alignment, and compatibility with perovskite devices. Its charge mobility and thermal durability, however, can limit device stability and scale-up.
Nickel oxide offers higher chemical and thermal robustness. By dispersing NiO nanoparticles within PTAA, the researchers sought to combine the interfacial and processing advantages of the polymer with the electrical and structural stability of an inorganic material.
The hybrid layer was incorporated into planar n–i–p perovskite solar cells. Detailed measurements showed that NiO addition:
- Produced a more favourable valence-band alignment.
- Approximately doubled measured hole mobility.
- Accelerated interfacial hole extraction.
- Suppressed charge-carrier recombination.
- Improved thermal robustness and slightly reduced moisture affinity.
The 10 mg/mL NiO formulation produced the best balance between improved transport and film uniformity. Higher concentrations increased nanoscale heterogeneity, likely because of particle aggregation.
Using the Pico for Small-Area Device Validation
Current–voltage measurements of the small-area perovskite cells were performed using a Keithley 2450 source meter under simulated AM1.5G illumination at 100 mW/cm² from a G2V Pico LED solar simulator. Each device had an active area of 0.09 cm² defined by an aperture mask.
Cells using the optimized PTAA:NiO layer achieved a champion efficiency of 20.76%, compared with 19.50% for cells using pristine PTAA. Short-circuit current density increased from 23.33 to 25.16 mA/cm².
The improvement was not limited to initial performance. Under ISOS-D-1 dark-storage testing, unencapsulated PTAA:NiO devices retained 86.5% of their initial efficiency after 6,000 hours. Devices based on pristine PTAA retained 70.9% over the same period.
The controlled illumination provided by the Pico allowed the researchers to compare the two hole-transport formulations under consistent test conditions. In this type of study, repeatable irradiance is essential because relatively small differences in photocurrent, voltage, or fill factor must be connected to the device design rather than fluctuations in the light source.
From Small Cells to Indoor IoT Power
The research did not stop at small-area cells.
The team extended the PTAA:NiO approach to 10 × 10 cm² perovskite minimodules containing 13 series-connected subcells. The modules were fabricated using vacuum-assisted crystallization and laser scribing to create the electrical interconnections.
The best hybrid-HTL minimodule reached:
- A power-conversion efficiency of 14.18%.
- An open-circuit voltage of 14.33 V.
- A short-circuit current of 66.63 mA.
- A fill factor of 64.14%.
After encapsulation, the PTAA:NiO modules retained 85.1% of their initial efficiency after 5,000 hours of storage testing. For accuracy, the large-area minimodule measurements in this study were conducted with a separate 15 × 15 cm LED solar simulator, while the G2V Pico was used for the small-area cell measurements.
Ten minimodules were then electrically combined to create a functional perovskite panel. The panel was integrated with a PM2.5 air-quality monitoring station to investigate whether perovskite photovoltaics could serve as an auxiliary energy source for low-power Internet-of-Things devices.
Under low-intensity indoor illumination of approximately 0.56 mW/cm², the perovskite panel produced a maximum voltage of 10.56 V. A monitoring station powered only by a 30,000 mAh battery operated for 74 hours. Adding the perovskite panel extended its operating time to 84 hours, with the additional operation occurring primarily during illuminated daytime periods.
This demonstration connects several development stages:
nanoparticle engineering → improved interface → higher-performing cell → stable minimodule → practical low-power system
It also shows why perovskite photovoltaics may be valuable beyond conventional outdoor solar panels. Their spectral response and strong low-light performance make them candidates for powering sensors and connected electronics in indoor environments.
Expanding into Nanocoatings and Materials Testing
Photovoltaics are only one part of Dr. Kumnorkaew’s research portfolio.
His background in nanoparticle self-assembly has also supported the development of transparent functional coatings for solar modules, solar farms, buildings, paints, and other surfaces.
One coating technology combines superhydrophobicity with dust repellency. Many water-repellent surfaces can still attract or retain dust. The team’s objective is to produce a transparent nanostructured coating that repels both water and particulate contamination without significantly reducing optical transmission.
The solar simulators are used in the laboratory to study the light transmission and degradation behaviour of these coatings. The samples are subsequently moved to the rooftop test site for outdoor validation.
The team is also developing solution-processed barrier coatings for packaging. Conventional multilayer packages often contain aluminum barrier films, which complicate recycling. NANOTEC’s work seeks to replace these metallic layers with polymer or nanoparticle-based coatings, including formulations suitable for food-contact paper packaging.
This combination of semiconductor research, chemistry, coatings, and field testing makes the laboratory a bridge between fundamental materials science and industrial implementation.
The Path Toward Pilot-Scale Manufacturing
The next stage of Dr. Kumnorkaew’s work is increasingly focused on scale.
Most current laboratory modules are approximately 10 × 10 cm, a size that can be accommodated by the existing Sunbrick. For pre-commercial demonstrations, however, he sees approximately 30 × 30 cm as a more representative target.
Larger illumination areas will be needed to characterize these devices under uniform conditions without relying on multiple sequential measurements. The team is also interested in long-duration light-soaking and stability experiments, faster changes between spectral and irradiance conditions, indoor low-light testing, and eventually AM0-type illumination for potential space-related research.
Long-term testing is particularly important in Thailand. The country’s high temperature and humidity provide a demanding environment for photovoltaic materials. Although indoor testing enables researchers to isolate individual variables, outdoor exposure reveals degradation mechanisms that may not appear under controlled laboratory conditions.
Dr. Kumnorkaew also identified a need within the photovoltaic community for two different categories of illumination:
- High-accuracy solar simulators for standardized performance measurements.
- More economical light sources for long-term soaking and exposure, where approximate spectral matching may be sufficient.
Separating these functions could allow researchers to reserve calibrated measurement systems for precise device characterization while using dedicated exposure systems for hundreds or thousands of hours of durability testing.
Ultimately, the laboratory’s objective extends beyond producing individual high-efficiency cells. Dr. Kumnorkaew is bringing academic researchers, national laboratories, equipment suppliers, and private companies together to develop the infrastructure required for pilot-scale perovskite manufacturing.
Advancing Perovskite Photovoltaics Through Better Materials and Better Measurements
The work at NANOTEC demonstrates that photovoltaic development is not a single experiment. It is a sequence of connected decisions:
At each stage, researchers need measurement tools that allow them to determine whether the observed improvement comes from the material itself or from variations in the test environment.
For Dr. Kumnorkaew and his collaborators, the Pico and Sunbrick support different parts of that process: rapid characterization of small experimental perovskite devices, routine laboratory measurements, larger-area samples, nanocoating studies, and future exploration of more varied illumination conditions.
At G2V Optics, we are proud to support NANOTEC’s work as the team continues moving perovskite photovoltaics from laboratory research toward scalable technologies and practical energy systems.
References
- Meeklinhom, S.; Towannang, M.; Gamonchuang, J.; Sinthiptharakoon, K.; Lapawae, K.; Sukgorn, N.; Rujisamphan, N.; Imhan, C.; Ratanatawanate, C.; Ruankham, P.; Wongratanaphisan, D.; Kanjanaboos, P.; Kaewprajak, A.; Kumnorkaew, P. “Perovskite Surface Treatment with Cu2O–MIL-53(Al) Metal–Organic Frameworks for Enhanced Efficiency and Stable Perovskite Solar Cells.” ACS Omega 11 (2026), 48972–48982. DOI: 10.1021/acsomega.5c12575.
- Sukgorn, N.; Kaewprajak, A.; Lapawae, K.; et al.; Kumnorkaew, P. “NiO Nanoparticle-Modified PTAA Hole Transport Layers for High-Efficiency and Stable Large-Area Perovskite Solar Cells.” ACS Applied Energy Materials 9 (2026), 7616–7630. DOI: 10.1021/acsaem.6c00778.
- Interview with Dr. Pisist Kumnorkaew, NANOTEC, Thailand.