Global Research in 2021 Enabled by Fluxim
/The year is nearly at an end and we’d like to share some of the impressive work that our customers around the globe have published throughout 2021.
With 97 papers published so far (and a few more to come before the year-end) it has been another record year for papers enabled with Fluxim’s software and measurement instruments.
Congratulations to all the researchers involved, we thank you for your continued trust in our tools.
Below you’ll find the papers that really stood out for us this year. PLUS a sneak preview of our latest video on PHELOS.
Organic Solar Cells
Have you tried to scale up your solar cells to large areas, just to discover that the efficiency was lower than the lab-scale device?
For both organic and perovksite solar cells, the scaling-up process is a challenge, also because of the high sheet resistance of the transparent conductive oxide (TCO). The use of a metallic grid in combination with the TCO is gaining interest as a solution to support the device upscaling.
Gregory Burwell and colleagues at Swansea University used Laoss to define the design parameters for an optimal large-area OPV. They carried on FEM simulation to estimate also the figures of merit for realistic large-area OPVs.
By combining simulation and experimental work they demonstrated that the scalability of devices with metallic grids improves significantly when grids are implemented at the micrometer scale. Their results show that metallic grids can be designed to develop large-area solution-processed solar cells with currently available fabrication techniques.
📜Parameterization of Metallic Grids on Transparent Conductive Electrodes for the Scaling of Organic Solar Cells
G. Burwell, N. Burridge, E. Bond, W. Li, P. Meredith, and A. Armin
Adv. Electron. Mater. (2021), 2100192,
Perovskite Solar Cells
The PCE of your lead-free Perovskite Solar Cell can increase by suppressing nonradiative recombination with post-processing of the formed perovskite film in vacuum.
📜Suppression of Nonradiative Recombination by Vacuum‐Assisted Process for Efficient Lead‐Free Tin Perovskite Solar Cells
Zhenxi Wan, Dewei Zhao et al.
Adv. Mat. Int. Volume 8, Issue 9 May 7, 2021, 2100135
doi.org/10.1002/admi.202100135
Prof. Dewei Zhao and collaborators at Sichuan University discovered that, by annealing a FA0.75MA0.25SnI3 perovskite film under high vacuum, is possible to reduce the trap density and non-radiative recombination in the layer, with a significant total improvement of the charge transport in the solar cell. With this simple experimental trick, the team almost doubled the PCE of the solar cell compared to the non-annealed device.
Paios helped them characterizing the solar cells. This all-in-one testing platform can be used to perform several opto-electrical characterizations, such as Transient Photocurrent (TPC), Capacitance-Voltage (CV), Charge Extraction (CE), and Light-Intensity-Dependent Measurements.
In this paper you can learn a technique for obtaining solution-processed perovskite solar cells with a PCE of 21%. The described method is suitable for the fabrication of large-area photovoltaics.
📜Potassium Thiocyanate‐Assisted Enhancement of Slot‐Die‐Coated Perovskite Films for High‐Performance Solar Cells
Fuzong Xu, Stefaan De Wolf, et al.
Small Sci. 2021, 2000044
Generally, only spin-coating can give high-efficiency perovskite solar cells when the active layer is deposited via solution. However, this technique is not suitable for large-area manufacturing.
The group of Prof. Stefaan De Wolf at the KAUST Solar Center (KSC) demonstrated that by assisting Slot-Die Coating with potassium thiocyanate (KSCN), it is possible to obtain a perovskite film with carrier mobility, lifetime, and diffusion length comparable to single crystals. Slot-die coating is now suitable for the fabrication of large-area solar cells thanks to the proposed protocol, which brings the quality of the deposited perovskites to the level of the other deposition methods.
The devices have been characterized, thoroughly using Paios. Several of the reported analyses, such as Transient Photovoltage (TPV), Transient Photocurrent (TPC), and Impedance Spectroscopy, have been performed with the all-in-one instrument PAIOS
Tandem Solar Cells
Organic−perovskite tandem solar cells can be processed from solution with a power conversion efficiency (PCE) of 25%. However, the volatility of the organic cations makes them unstable under solar irradiation.
📜Tuning of the Interconnecting Layer for Monolithic Perovskite/ Organic Tandem Solar Cells with Record Efficiency Exceeding 21%
Pang Wang, Ardalan Armin, and Tao Wang et al.
Nano Lett. 2021, 21, 18, 7845–7854
https://doi.org/10.1021/acs.nanolett.1c02897
Recently, researchers at the Wuhan University of Technology made a tandem PSC with a PCE of 21% and stable efficiency for 160 days. The key to good performance is the choice of the hole-transporting material (HTM) between the perovskite and organic layer. They discovered that the polymer polyTPD is an ideal HTM. This connects the wide-bandgap inorganic perovskite CsPbI2Br and the narrow-bandgap organic semiconductor PM6:Y6-BO. PolyTPD shows no parasitic photon absorption for wavelengths between 300 and 1000 nm and had ideal hole mobility with quasi-ohmic behavior, allowing a voltage loss of only 0.06 V.
The simulation software Setfos helped them predict why this material was the best choice for their solar cells.
This is a great opening for a paper: “perovskite/silicon tandem photovoltaics (PVs) promise to accelerate the decarbonization of our energy systems.”
Monolithic pero/Si tandem solar cells have already reached a power conversion efficiency (PCEs) of over 29%, which surpassed the world record of silicon single-junction solar cells.
Researchers at the Helmholtz-Zentrum Berlin and the University of Potsdam developed a diagnosis method that can help increase the PCE even further. They demonstrated that performance losses in tandem solar cells should be studied on complete tandem devices with both photoluminescence (PL) and electroluminescence (EL).
📜Revealing Fundamental Efficiency Limits of Monolithic Perovskite/Silicon Tandem Photovoltaics through Subcell Characterization
Felix Lang, Steve Albrecht, Martin Stolterfoht et al.
ACS Energy Letters 0, 6
DOI: 10.1021/acsenergylett.1c01783
Tandem solar cells are much more than the combination of multiple junctions. Interfaces, contact layers, and inhomogeneities among the subcells all influence the tandem performance. Generally, the ideal solar cell is the device in which the quasi-fermi level splitting (QFLS) in the sub-cell extracted by PL or EL is identical. If not, the solar cell has energy losses.
The simulation software Setfos helped them demonstrate that even an energy offset of 0.3 eV between the perovskite and the ETL leads to a significant difference in the QFLS extracted via PL or EL. Such a solar cell would have reduced performance due to interface recombination.
OLEDs
A bright future for blue OLEDs.
Congratulations to Nicola Gasparini and colleagues who developed the blue TADF OLEDs with the highest reported EQE to date (EQE = 41.2%).
📜High efficiency blue organic light-emitting diodes with below-bandgap electroluminescence
Vasilopoulou, M., Mohd Yusoff, A.R.b., Daboczi, M. et al.
Nat Commun 12, 4868 (2021). doi.org/10.1038/s41467-021-25135-z
The team designed blue OLEDs with a new Hole Transport Material (HTM). By engineering the formation of exciplex excitons at the EML/ETL interface and subsequent FRET they managed to fabricate OLEDs with high efficiencies and turn-on voltage below band-gap.
The device lifetime is longer than previously reported blue OLEDs, even if degradation due to the instability of the excited host molecule (typical in TADF OLEDs) is still an issue.
The simulation software Setfos from FLUXiM AG helped them extracting the dipole orientation of the TADF emitter from the analysis of angle-dependent PL spectra.
Quantum Dot LECs
Perovskite Quantum Dot (QD) Light-Emitting Electrochemical Cells (LECs) are easy to fabricate and could be a low-cost alternative to QD-LEDs.
📜 Highly Soluble CsPbBr 3 Perovskite Quantum Dots for Solution-Processed Light-Emission Devices
Y. Liu, J. Wang, et al.
ACS Applied Nano Materials Article ASAP
DOI: 10.1021/acsanm.0c02797
Profs. Ludvig Edman and JIA WANG at Umeå University fabricated several types of light-emitting devices with a solution deposited perovskite QDs emissive layer. They successfully demonstrated that ions are liberated from the PeQD structure during device operation.
These ions are mobile and perform electrochemical doping, which makes the device functioning as a LEC even without an external electrolyte.
The best-performing PeQD-LEC delivered a peak luminance of 1090 cd/m2 at 6.8V.
These researchers simulated their LECs with Setfos. Their results demonstrate how a well-thought optical simulation can predict the behavior of the device before the actual fabrication. The simulation anticipated that by introducing a PVK spacer of a given thickness, the luminance would have increased by 28% with respect to the reference device. The actual experiment showed an improvement of 26%.
Have you ever wished for a spectrometer that can perform angle resolved EL and PL?
If you haven’t you might do after watching this 👇
