Naphthodithiophene-2,l,3-benzothiadiazole copolymers for bulk heterojunction solar cells

摘要

Two newly synthesized naphthodithiophene-based copolymers, PNB, exhibit a low optical bandgap of ~ 1.64 eV with which the solar cells fabricated from the blend of PNB and PC_(70)BM afforded a power conversion efficiency of 5.3% with external quantum efficiency over 60% in a broad spectral range. Organic/polymeric photovoltaic (PV) cells have received considerable attention from both academia and industry due to the demand for inexpensive and renewable energy sources.1 Some examples of organic PV applications have recently been demonstrated.2 The fast growing development of bulk heterojunction (BHJ) PV cells based on solution-processable p-type-conjugated polymers and n-type fullerene derivatives has recently made tremendous progress with power conversion efficiencies (PCE) reaching greater than 7%.3 Such great advancement is mainly due to the development of new low bandgap p-type materials with strong and broad absorption, the effective fabrication processes such as solvent annealing, thermal annealing and the use of solvent additives for proper control of the interpenetrating network morphology of a donor and acceptor blend as well as the optimized device structure.