Predicting Efficiency of Organic Optoelectronic Devices: a multiscale protocol from Charge-Transfer Mechanisms to Device-Level Performances

Organic semiconductors hold great promise for low-cost, flexible and wearable optoelectronics, yet their performance remains limited by incompletely understood charge- and energy-transfer processes occurring at donor-acceptor interfaces and within disordered molecular packings. In this talk we present a unified multiscale computational protocol - combining classical molecular dynamics with quantum-mechanically derived force fields (QMD-FF), density functional theory (DFT/TDDFT), Fermi's Golden Rule (FGR) rate theory, and kinetic Monte Carlo (KMC) or Pauli master-equation simulations - developed and applied across a series of studies to rationalize and predict the optoelectronic performance of organic materials. We will show how this framework explains the superior efficiency of Y6-based non-fullerene acceptors over IDIC derivatives, by resolving multiple photoinduced charge-separation pathways and identifying fast non-radiative charge recombination as the dominant loss channel correlating with power conversion efficiency across a family of donor–acceptor blends. We then extend the approach to ternary solar cells, demonstrating that Förster resonance energy transfer between two donor molecules can funnel absorbed energy toward the kinetically more efficient donor-acceptor pair, and that even subtle structural differences between donors can produce dramatically different charge-transfer kinetics - challenging purely qualitative design strategies. Building on these mechanistic insights, we present a first-principles framework for predicting open-circuit voltage and short-circuit current density directly from redox potentials and absorption spectra, using the Franck-Condon weighted density of states as a genuinely predictive quantity that also captures temperature-dependent behavior, validated against eight experimental devices spanning fullerene and non-fullerene chemistries. Finally, we demonstrate the generality of this methodology beyond solar cells by investigating thermal disorder effects on hole polaron formation and charge mobility in acene crystals, showing that site-energy fluctuations (rather than electronic coupling fluctuations) govern mobility suppression relative to ordered crystals. Together, these studies illustrate how a consistent, physically grounded computational protocol can move from mechanistic rationalization to quantitative, predictive design of organic optoelectronic materials, offering a practical route toward accelerated screening of donor–acceptor combinations for next-generation photovoltaic and semiconductor devices.