Photo Stabilization of p-i-n Perovskite Solar Cells with Bathocuproine: MXene.

Interface engineering is one of the promising strategies for the long-term stabilization of perovskite solar cells (PSCs), preventing chemical decomposition induced by external agents and promoting fast charge transfer. Recently, MXenes-2D structured transition metal carbides and nitrides with various functionalization (O, -F, -OH) have demonstrated high potential for mastering the work function in halide perovskite absorbers and have significantly improved the n-type charge collection in solar cells. This work demonstrates that MXenes allow for efficient stabilization of PSCs besides improving their performances. A mixed composite bathocuproine:MXene, that is, (BCP:MXene) interlayer, is introduced at the interface between an electron-transport layer (ETL) and a metal cathode in the p-i-n device structure. The investigation demonstrates that the use of BCP:MXene interlayer slightly increases the power conversation efficiency (PCE) for PSCs (from 16.5 for reference to 17.5%) but dramatically improves the out of Glove-Box stability. Under ISOS-L-2 light soaking stress at 63 ± 1.5 °C, the T80 (time needed to reduce efficiency down to 80% of the initial one) period increases from 460 to > 2300 hours (h).

Copper Iodide Interlayer for Improved Charge Extraction and Stability of Inverted Perovskite Solar Cells.

Nickel oxide (NiO) is one of the most promising and high-performing Hole Transporting Layer (HTL) in inverted perovskite solar cells due to ideal band alignment with perovskite absorber, wide band gap, and high mobility of charges. At the same time, however, NiO does not provide good contact and trap-free junction for hole collection. In this paper, we examine this problem by developing a double hole transport configuration with a copper iodide (CuI) interlayer for efficient surface passivation. Transient photo-current (TPC) measurements showed that Perovskite/HTL interface with CuI interlayer has an improved hole injection; CuI passivation reduces the concentration of traps and the parasitic charge accumulation that limits the flow of charges. Moreover, we found that CuI protect the HTL/perovskite interface from degradation and consequently improve the stability of the cell. The presence of CuI interlayer induces an improvement of open-circuit voltage VOC (from 1.02 V to 1.07 V), an increase of the shunt resistance RSH (100%), a reduction of the series resistance RS (-30%), and finally a +10% improvement of the solar cell efficiency.