Sungkyunkwan University (SKKU) research team, led by Professors Taeyeon Kim and Doo-Hyun Ko, Department of Chemistry, has recently published a comprehensive review titled "Carrier Dynamics in Nonfullerene Acceptor Organic Photovoltaics through Ultrafast Spectroscopy" in the prestigious international journal ACS Nano.
Unlike conventional rigid silicon-based devices, organic optoelectronic devices can be made as light, flexible, and transparent as plastic, and the recent development of new nonfullerene acceptor materials has driven a dramatic rise in the efficiency with which light is converted into electrical energy. Yet the microscopic principles governing what happens inside these materials in the instant that light is absorbed and electricity is produced have remained an open challenge, with different research groups arriving at conflicting interpretations.
In response, the team consolidated the body of research on "ultrafast spectroscopy", which measures light–matter interactions occurring on femtosecond (one quadrillionth of a second) timescales. The review systematically maps three principal techniques (transient absorption (TA), pump–push–probe (PPP), and two-dimensional electronic spectroscopy (2DES)) onto the steps each can resolve and the limitations each carries. It also unifies the terminology for intermediate states that had been used inconsistently across research groups and sets out criteria that must be satisfied before an observed signal can be assigned to a particular stat showing that conflicting reports on the benchmark material PM6:Y6 may arise much from differences in experimental conditions, such as excitation wavelength and film processing protocols as from genuine physical differences.
The review further summarizes recent studies showing that the molecular structure of nonfullerene acceptors, their nanoscale crystallinity, and the quadrupole moments generated by the molecules lower energy barriers at the interface and suppress charge recombination, distilling these findings into design guidelines for materials that can secure both efficiency and stability. It also identifies operando measurements under device operating conditions as a key challenge for the future.
This study provides a vital "roadmap" for engineers and scientists to design better materials, ultimately leading to more efficient, durable, and commercially viable solar energy solutions. This achievement underscores SKKU’s commitment to leading global innovation in green technology and solving the world’s energy challenges through rigorous scientific inquiry.