PhD & Postdoc

Hiroshi Tanaka

Organic Electronics · Osaka University

Hiroshi Tanaka investigates how the molecular weight distribution of non-fullerene acceptor molecules controls the nanoscale morphology of the bulk heterojunction blend layer in organic photovoltaic cells, working under Prof. Kazuo Mori at Osaka University's Institute for Advanced Co-Creation Studies. Commercial NFA synthesis inevitably produces polydisperse batches whose broad Mw distribution broadens the crystalline domain size distribution and suppresses charge-carrier mobility — but the relationship has never been quantified with morphological resolution. Hiroshi has established a preparative GPC fractionation protocol that isolates narrow NFA fractions at Mw spacings of 200 Da, then maps the resulting morphology evolution using in situ GIWAXS at the SPring-8 synchrotron during thermal annealing. He has discovered that a narrow Mw window centred 15% above the number-average produces the optimal combination of crystallite size (7 nm) and face-on orientation index (0.82) in PM6:IT-4F blends, yielding a certified power conversion efficiency of 17.3% — the highest yet reported for this particular system. His collaboration with Panasonic's advanced research department and a NEDO innovation grant co-PI position are translating this understanding into production-relevant coating process control specifications.

Thesis Topic

Non-Fullerene Acceptor Morphology Control in Organic Photovoltaic Blends via Precise Molecular Weight Fractionation and In Situ GIWAXS Characterisation

Transition Signals