Enhanced performance and stability in PBDTTT-C-T : PC₇₀ BM polymer solar cells by optimizing thickness of NiOx buffer layers

We report efficient polymer solar cells (PSCs) based on PBDTTT-C-T : PC 70 BM with a NiO x anode buffer layer (thickness of 3–15 nm) prepared by radio-frequency magnetron sputtering deposition. The PSC with the optimum NiO x buffer layer thickness of 9 nm showed the highest power conversion efficiency of 7.42% with V oc of 0.75 V, J sc of 15.82 mA cm −2 and FF of 62.5%, which was higher than that of the PSCs with a PEDOT : PSS buffer layer. Moreover, compared with the PSCs with a PEDOT : PSS buffer layer, the PSCs with the optimum NiO x buffer layer exhibited a better stability under N 2 atmosphere. The results indicate that the sputtered 9 nm thick NiO x buffer layer is superior to the PEDOT : PSS buffer layer not only for better performance but also for improved long-term stability. The optimized NiO x buffer layer thickness possesses an appropriate energy level matching with PBDTTT-C-T, which results in effective hole collection and improved photovoltaic performance.