Solution-processable n-doped graphene-containing cathode interfacial materials for high performance organic solar cells
Interface engineering is a very critical factor in achieving high photovoltaic performance for large area, printable, flexible and low cost organic solar cells (OSCs). Here, we developed a solution-processable n-doped graphene cathode interfacial material (CIM) PDINO-G for the OSCs by adding graphenes to a classical material PDINO ((N, N-dimethyl-ammonium N-oxide) propyl perylene diimide). The dispersed graphene in PDINO-G was n-doped by the nitroxide radical of N-oxide in PDINO, which was certified by the results of ESR, Raman and XPS. The n-doped PDINO-G CIM possesses the increased conductivity, lower work function, reduced charge recombination and increased charge extraction rate. Before that, the n-doped graphene has been prepared only on the graphene surface of chemical vapor deposited (CVD) graphenes film without solution processability. The effect of the CIM on the photovoltaic performance of the OSCs was studied by selecting the photovoltaic model system of PTQ10 as donor and IDIC-2F as acceptor. The OSCs based on PTQ10: IDIC-2F with PDINO-G CIM demonstrated the best power conversion efficiency (PCE) of 13.01%, which is significantly improved in comparison with the devices without graphene modification on the PDINO CIM (12.23%). The universality of the high performance PDINO-G CIM was verified on the two other photovoltaic systems based on PTQ10: IDIC and PM6:Y6. Especially, the single junction bulk heterojunction OSCs based on PM6:Y6 with PDINO-G CIM displayed high PCE of 16.52% (average PCE of (16.3±0.2)%). The results indicate that the n-doped PDINO-G is an excellent CIM for OSCs. This PDINO-doped graphene could be applied in other optoelectronic devices such as tandem OSCs, organic light emitting diodes, and high-performance perovskite solar cells as the cathode interfacial materials in considering its advantages of solution-processing, lower work-function and higher conductivity.