In this work, we use rf magnetron sputtering to deposit at room temperature a ZnO thin film on top of a photoactive material based on P3HT:PCBM blend for organic photovoltaic devices. We investigate the influence of the sputtering conditions on the ZnO crystallinity, on the substrate layer nanoscale morphology and on the photovoltaic device performances. We show that, under appropriate sputtering conditions, the modification of the P3HT:PCBM film causes no functional damage of the photoactive layer, and leads to an improved performance of the photovoltaic devices.

In this paper, we report on the photovoltaic properties of conventional organic photovoltaic solar cells integrating a sputtered ZnO interfacial film deposited on the absorber P3HT:PCBM layer. An emphasis has been put on the influence of the annealing temperature and time for restoring and controlling the P3HT:PCBM/ZnO interface morphology, which can be damaged by the sputtering process. We show a significant improvement in the current–voltage (J–V) characteristics upon annealing up to 160 °C. This is evidenced by the reduction of the S-shape of these curves systematically observed for the cells integrating thick (100 nm) sputtered ZnO films. This approach was also highlighted on cells containing thinner (20 nm) ZnO films using a longer annealing process at 140 °C, which led to a significant improvement of the power conversion efficiency compared with the value recorded in as-prepared cells or in cells with no interfacial ZnO layer. These photovoltaic performances have been related to the change of the morphology of the absorber layer and to the vertical phase segregation of P3HT:PCBM at the interface with ZnO. Optical microscopy, scanning electron microscopy and atomic force microscopy have been performed in order to confirm this approach.

Two simple carbazole-based hole-transporting materials (HTMs) substituted with fused aromatic rings (Cz-N and Cz-Pyr) were synthesized in high yield and tested in perovskite solar cells (PSC). Cz-Pyr appears as a very promising HTM owing to its easy synthesis, relatively high T_g and high efficiency, outperforming the reference HTM Spiro-OMeTAD in PSCs.