Current computer simulations of organic thin films are getting the arrangement of molecules wrong even when they get the average correct.
April 23, 2026
Original Paper
Revealing full molecular orientation distributions in organic thin films by nonlinear polarimetry
arXiv · 2604.16692
The Takeaway
Organic thin films are the building blocks of flexible electronics and phone screens. Nonlinear polarimetry can now reconstruct the full distribution of how these molecules are tilted and turned. Standard models usually only report an average orientation, which hides the messy reality of the material. This new method proves that molecules are often distributed in ways that completely contradict existing molecular dynamics simulations. Accurately mapping these distributions is the only way to build more efficient solar cells and light-emitting diodes.
From the abstract
The performance of organic optoelectronic devices is critically dependent on how molecules orient within organic thin films. Yet, standard characterization techniques only reveal the first and second moments of the molecular orientation distribution. This limitation obscures the true molecular arrangement, as diverse distributions can yield identical low-order averages while exhibiting distinct functional properties. Here, we bridge this gap by combining multi-harmonic nonlinear polarimetry (sec