Obaid Alqahtani’s work on structure-property relationships in small molecule organic solar cells (SM-OSCs) has been officially published online at Advanced Energy Materials. SM-OSC devices convert sunlight into power like commercial solar panels, but this new technology could significantly lower the cost of solar power because it can be printed from inks in a roll-to-roll newspaper fashion, is light-weight and flexible, and is made from earth-abundant, non-toxic materials.
Alqahtani’s work explains how the performance of SM-OSCs depends on the details of the nanostructure, which can be tuned via processing solvent and choice of molecular side-chain. In particular, it is demonstrated that high purity nano-domains results in low/delayed charge generation and severe charge trapping, but that small, mixed domains alleviates such problems to enable high performance in these devices. Future work toward commercialization should target such nanostructure for high solar power conversion efficiencies.
The work involved a large round-robin collaboration with groups across the globe including King Abdullah University of Science and Technology (KAUST, Saudi Arabia), Stanford University (USA), University of Potsdam (Germany), and University of Queensland (Australia).
Terry McAfee has joined the Collins Research Group as postdoctoral researcher. He obtained his PhD in physics from North Carolina State University under Professor Harald Ade. His thesis was titled “Characterization and control of morphology in organic photovoltaic devices.” Recently, he completed postdoctoral work at Tulane University under Professor Wayne Reed developing an Automatic Continuous Online Monitoring of Polymerization (ACOMP) system. Terry joins the Collins group to develop a new Environmental Resonant Soft X-ray Scattering instrument which will enable in-situ/in-operando structural measurement of organic materials.
Thomas Ferron’s work on quantitative spectral RSoXS analysis has been published in Physical Review Letters.
Measurement of buried molecular interfaces enabled by resonant X-ray scattering analysis
We demonstrate a new quantitative X-ray scattering analysis that probes 3D molecular nanostructures and even buried interfaces between those structures. These organic nanomaterials are of increasing impact in bottom-up assembly, electronic devices, and biomimetic applications, but their internal structure is difficult to probe due to light elements and no or low crystallinity. For example, only planar interfaces were previously accessible with laborious and disruptive chemical tagging. This new technique eliminates the need for tagging and can investigate nonplanar interfaces more commonly found in nature. The technique is a leap in X-ray science because the analysis requires absolute scattering intensity at an absorption edge where low sample penetration depths preclude the use of calibration standards. Each molecule has a unique fingerprint encoded as a function of photon energy, which the technique uses to chemically separate components of the nanostructure. Through our new spectral analysis, complex molecular structures composed of any number of unique molecular species can now be fully analyzed.
The Collins Group has received the DOE Early Career Award, a 5 year competitive grant that includes tenure track faculty at all US universities and national laboratories. This year out of approximately 700 submissions, only 59 individuals were awarded. (See release by WSU and DOE). The grant entitled “Polarized resonant X-ray scattering to measure molecular orientation and conformation in organic nanostructures” will enable Collins’ continued state-of-the-art research in developing resonant X-ray techniques to reveal order in molecular materials, structures, and devices.
Keith Hillaire has received his Bachelor of Science in Physics from WSU. His thesis “Color-tuning polymer-based organic light emitting diodes through the addition of a cosolvent” involved research on the how processing can affect the nanomorphology and therefore the color of novel polymer OLEDs. He begins his graduate studies in the North Carolina State University Physics PhD program. Congratulations Keith!
Matthew Waldrip has received his Bachelors in Science with Honors from WSU. He worked with the Collins group developing nanosecond pump-probe methods to investigate charge generation in organic solar cells. His thesis is entitled “Disentangling the effect of pure fullerene nanodomains on charge generation and recombination in organic solar cells.” He starts his graduate studies in the Physics PhD program at Wake Forest University. Congratulations Matthew!
Michael Pope has successfully defended his masters project entitled “Using resonant X-ray scattering to determine how structure controls the charge generation process in PCPDTBT:PC70BM solar cells.” Congratulations Michael!
The National Science Foundation has awarded a proposal lead by the Collins Group on the “Development of Environmental Control for Resonant X-ray Scattering on Organic Samples.” Co-PIs include Enrique Gomez of Penn State University and Harald Ade of NC State University. The new instrument will be constructed at the Advanced Light Source of Lawrence Berkeley National Laboratory and will enable in-situ or in-operando studies of nanostructure in liquid and electrochemical environments with the sample fully exchangeable with existing transmission electron microscopes. For more information follow the link.
Michael Pope has given his first public science talk at the Electronic Materials Conference at the University of Delaware. The talk “In Pursuit of Reproducible Structure-Property Relationships in Organic Solar Cells” detailed in his first study of structure-property relationships in all-polymer organic solar cells using our One Sample method which involved in-situ dynamics measurement using time-resolve photoluminescence (TRPL), transient photovoltage (TPV), and time-delayed collection field (TDCF). The nanostructure of the devices themselves were then characterized at the Advanced Photon Source using resonant and traditional X-ray experiments.
Obaid Alqahtani has successfully defended his masters project and obtained his degree from the physics program at WSU. His project involved resonant X-ray reflectivity measurements on small molecule thin films and multilayers deposited via physical vapor deposition. He also lead our collaboration with the Pierre Beaujuge group at King Abdullah University of Science and Technology on X-ray nanostructure investigations of their small-molecule-based organic solar cells. Obaid now returns to Saudi Arabia to teach university physics.