Order enables efficient electron-hole separation at an organic heterojunction with a small energy loss

• DOI: 10.1038/s41467-017-02457-5
• Publication Date: 2018-01-12T15:03:31Z
• Authors: S. Matthew Menke; Alexandre Cheminal; Patrick Conaghan; Niva A. Ran; Neil C. Greehnam; Guillermo C. Bazan; Thuc-Quyen Nguyen; Akshay Rao; Richard H. Friend
• Keywords: Photoexcitation; Acceptor; Quantum Efficiency; Charge carrier

Donor-acceptor organic solar cells often show low open-circuit voltages (V OC) relative to their optical energy gap (E g) that limit power conversion efficiencies ~12%. This loss is partly attributed the offset between E g and of intermolecular charge transfer (CT) states at donor-acceptor interface. Here we study generation occurring in PIPCP:PC61BM, a system with very driving for initial separation g-E CT ~ 50 meV) high internal quantum efficiency (η IQE 80%). We track strength electric field generated separating electron-hole pair by following transient electroabsorption response, find while localised are formed rapidly (<100 fs) after photoexcitation, free charges not until 5 ps photogeneration. In electronic disorder (Urbach <27 consider able outcompete trap-assisted non-radiative recombination state.