Suchergebnisse

Antimonene, a novel group 15 two-dimensional material, is functionalized with a tailormade perylene bisimide through strong van der Waals interactions. The functionalization process leads to a significant quenching of the perylene fluorescence, and surpasses that observed for either graphene or black phosphorus, thus allowing straightforward characterization of the flakes by scanning Raman microscopy. Furthermore, scanning photoelectron microscopy studies and theoretical calculations reveal a remarkable charge-transfer behavior, being twice that of black phosphorus. Moreover, the excellent stability under environmental conditions of pristine antimonene has been tackled, thus pointing towards the spontaneous formation of a sub-nanometric oxide passivation layer. DFT calculations revealed that the noncovalent functionalization of antimonene results in a charge-transfer band gap of 1.1 eV ; We thank the ESCA microscopy beamline team at Elettra for technical assistance with the scanning X‐ray photoelectron microscopy measurements. The research leading to these results has received partial funding from the European Union Seventh Framework Programme under grant agreement no. 604391 Graphene Flagship. We thank the Deutsche Forschungsgemeinschaft (DFG‐SFB 953 "Synthetic Carbon Allotropes", Projects A1 and C2), the Interdisciplinary Center for Molecular Materials (ICMM), and the Graduate School Molecular Science (GSMS) for financial support. We thank the MINECO (Spain) for financial support through the "María de Maeztu" Programme for Units of Excellence in R&D (MDM‐2014‐0377) and the projects: MAT2016‐77608‐C3‐1P and 3P, as well as MAT2014‐52477‐C5‐5 and MAT2015‐66888‐C3‐3‐R. Co‐funding from UE is also acknowledged. G.A. thanks the EU for a Marie Curie Fellowship (FP7/2013‐IEF‐627386), and the FAU for the Emerging Talents Initiative (ETI) grant #WS16‐17_Nat_04

AbstractA critical bottleneck for improving the performance of organic solar cells (OSC) is minimising non-radiative losses in the interfacial charge-transfer (CT) state via the formation of hybrid energetic states. This requires small energetic offsets often detrimental for high external quantum efficiency (EQE). Here, we obtain OSC with both non-radiative voltage losses (0.24 V) and photocurrent losses (EQE > 80%) simultaneously minimised. The interfacial CT states separate into free carriers with ≈40-ps time constant. We combine device and spectroscopic data to model the thermodynamics of charge separation and extraction, revealing that the relatively high performance of the devices arises from an optimal adjustment of the CT state energy, which determines how the available overall driving force is efficiently used to maximize both exciton splitting and charge separation. The model proposed is universal for donor:acceptor (D:A) with low driving forces and predicts which D:A will benefit from a morphology optimization for highly efficient OSC. ; N.G. acknowledges the Imperial College Research Fellowship scheme. C.J.B. gratefully acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), Project no. 182849149-SFB 953. C.J.B. gratefully acknowledges financial support through the "Aufbruch Bayern" initiative of the state of Bavaria (EnCN and SFF) and the Bavarian Initiative "Solar Technologies go Hybrid" (SolTech) and funding from DFG project DFG INST 90/917. C.C.L. thanks the European Union for the financial support. G.C. acknowledges the support from the PRIN 2017 Project 201795SBA3—HARVEST.