Efficient and Highly Air Stable Planar Inverted Perovskite Solar Cells with Reduced Graphene Oxide Doped PCBM Electron Transporting Layer

Reduced graphene oxide (rGO) is added in the [6,6]-Phenyl-C61-butyric acid methyl ester (PCBM) electron transport layer (ETL) of planar inverted perovskite solar cells (PSCs), resulting in a power conversion efficiency (PCE) improvement of ≈12%, with a hysteresis-free PCE of 14.5%, compared to 12.9% for the pristine PCBM based device. The universality of the method is demonstrated in PSCs based on CH3NH3PbI3−xClx and CH3NH3PbI3 perovskites, deposited through one step and two step spin coating process, respectively. After a comprehensive spectroscopic characterization of both devices, it is clear that the introduction of rGO in PCBM ETL results in an important increase of the ETL conductivity, together with reduced series resistance and surface roughness. As a result, a significant photoluminescence quenching of such perovskite/ETL is observed, confirming the increased measured short circuit current density. Transient absorption measurements reveal that in the rGO-based device, the relaxation process of the excited electrons is significantly faster compared to the reference, which implies that the charge injection rate is significantly faster for the first. Furthermore, the light soaking effect is significantly reduced. Finally, aging measurements reveal that the rGO stabilizes the ELT/perovskite interface, which results in the stabilization of perovskite crystal structure after prolonged illumination

Extending the Continuous Operating Lifetime of Perovskite Solar Cells with a Molybdenum Disulfide Hole Extraction Interlayer

Solution-processed organic–inorganic lead halide perovskite solar cells (PSCs) are considered as one of the most promising photovoltaic technologies thanks to both high performance and low manufacturing cost. However, a key challenge of this technology is the lack of ambient stability over prolonged solar irradiation under continuous operating conditions. In fact, only a few studies (carried out in inert atmosphere) already approach the industrial standards. Here, it is shown how the introduction of MoS2 flakes as a hole transport interlayer in inverted planar PSCs results in a power conversion efficiency (PCE) of ≈17%, overcoming the one of the standard reference devices. Furthermore, this approach allows the realization of ultrastable PSCs, stressed in ambient conditions and working at continuous maximum power point. In particular, the photovoltaic performances of the proposed PSCs represent the current state-of-the-art in terms of lifetime, retaining 80% of their initial performance after 568 h of continuous stress test, thus approaching the industrial stability standards. Moreover, it is further demonstrated the feasibility of this approach by fabricating large-area PSCs (0.5 cm2 active area) with MoS2 as the interlayer. These large-area PSCs show improved performance (i.e., PCE = 13.17%) when compared with the standard devices (PCE = 10.64%)