Titanium-carbide MXenes for work function and interface engineering in perovskite solar cells

Abstract

In order to improve the efficiency of perovskite solar cells (PSCs), careful device design and tailored interface engineering are needed to enhance optoelectronic properties and the charge extraction process at the selective electrodes. Here, we use two-dimensional transition metal carbides (the MXene Ti3C2TX) with various termination groups (TX) to tune the work function (WF) of the perovskite absorber and the TiO2 electron transport layer (ETL), and to engineer the perovskite/ETL interface. Ultraviolet photoemission spectroscopy measurements and Density Functional Theory calculations show that the addition of Ti3C2TX to halide perovskite and TiO2 layers permits to tune the materials' WFs, without affecting other electronic properties. Moreover, the dipole induced by the Ti3C2TX at the perovskite/ETL interface can be used to change the band alignment between these layers. The combined action of WF tuning and interface engineering can lead to substantial performance improvements in MXene-modified PSCs, as shown by the 26% increase of power conversion efficiency and hysteresis reduction with respect to reference cells without Mxene.

Recent Advances in 2D MXenes for Photodetection

“…[ 13,14 ] As schematically illustrated in Figure a, the so‐called MXenes were initially evolved from layered and hexagonal MAX phases through selectively etching away the A element, which is mainly from III‐A and IV‐A groups. [ 15,16 ] The obtained MXenes exhibit a similar configuration of the X layer sandwiched by the double neighbored M layers. Structurally, the derived MXenes inherit hexagonal symmetry from the parent MAX phases, as displayed in Figure 1b.…”

“…Namely, surface functional terminations are able to evidently influence intrinsic physical, chemical, and mechanical properties of MXenes, including work functions, electronic band structures, and hydrogen evolution reactivity. [ 16,37–40 ] Notably, metallic conductivity (> 10 4 S cm −1 for Ti 3 C 2 T x ) and surface hydrophilicity enable various electronic applications of MXenes, including transparent contacts and conductive fillers. [ 41,42 ] Apart from the reported metallic MXenes, semiconducting MXenes have been predicted and synthesized as well.…”

Chlorosome‐Like Molecular Aggregation of Chlorophyll Derivative on Ti3C2Tx MXene Nanosheets for Efficient Noble Metal‐Free Photocatalytic Hydrogen Evolution

“…MXenes are a new family of 2D nanostructured materials originally reported in 2011. [ 23 ] The excellent electrochemical properties of MXenes make them widely applicable for electromagnetic interference shielding, [ 24–25 ] photodegradation, [ 26 ] photovoltaics, [ 27–28 ] electrochemical catalysis, [ 29 ] supercapacitors, and lithium ion batteries. [ 30–32 ] MXenes are prepared from MAX phases by etching the A layer (usually Al or Si) with a strong acid solution such as HF or LiF/HCl.…”

Laser‐Generated Supranano Liquid Metal as Efficient Electron Mediator in Hybrid Perovskite Solar Cells

“…To confirm the mechanism of charge extraction by supranano‐LMCs in the film, ultraviolet photoelectron spectroscopy (Figure S9, Supporting Information) has been further employed to explore the band structure of the supranano‐LMCs and perovskite, respectively. [ 26 ] As shown in Figure 4g, the conduction band minimum (CBM) of the supranano‐LMCs shell is about 3.82 eV, which is close to that of CsFAMA‐LMCs (–3.90 eV). Photogenerated electrons in this case are much easier to transfer through GBs compared to the case without embedding of LMCs at GBs, which is in agreement with a recent report by Sargent's group.…”