Large Area and High‐Efficiency MXene–Silicon Solar Cells by Organic Enhanced Dispersity and Work Function

Abstract

2D transition metal carbides and nitrides (MXenes), as an emerging class of 2D materials, [1,2] have gained significant attention in recent years. MXenes are usually obtained by etching the "A" layer from its parent ternary MAX phase, expressed by the formula M n þ 1 X n T x , where M stands for an early transition metal (Ti, Mo, Nb, or V), X stands for carbide (C) or nitride (N) or both, and T x denotes surface terminated functional groups (F, OH, and O). [3] Because of their good hydrophilicity, abundant surface functional groups, high conductivity, excellent photothermal and photoelectric effects, and so on, MXenes were widely used in electromagnetic shielding, [4,5] electrochemical energy storage, [6] photodetectors, [7] biomedicine, [8] separation, [9] sensors [10] and seawater desalination, [11] and other fields.In addition to these applications, given their attractive electrical conductivity and transparency, MXene films have also been demonstrated to be able to substitute the traditional expensive transparent conducting electrodes in photovoltaic (PV) devices. [12][13][14][15][16][17] For example, Yang et al. report on the use of pure MXene layer as an electron transport layer (ETL) in perovskite solar cell (PSC), and achieved the champion power conversion efficiency (PCE) of 18.34%. [12] Yu et al. by using a UV ozone treatment or through a treatment with N 2 H 4 , thus tuned the work function of Ti 3 C 2 T x MXene in a range from 4.08 to 4.95 eV. Then the MXene films with different work functions are studied as the electron and hole collection buffer materials of organic solar cells. [13] In fact, the work function of MXene can be theoretically adjusted from less than 2.0 eV to more than 6.0 eV, which illustrated that MXene was a potential candidate as a hole-selective contact layer in silicon (Si) solar cells. The first MXene-contacted Si solar cell was devised by Fu et al. in 2019. They reported that the formation of an Ohmic junction of the metallic MXene to the n þ -Si surface can effectively extract the photogenerated electrons, reduce the contact resistance, and inhibit the charge carrier recombination, giving the devices the highest PCE of 11.5% with an area of 1.21 cm 2 . [14] Yu et al. also showed that the Ti 3 C 2 T x can facilitate the charge separation at the MXene-Si heterojunction, and obtained an efficiency of 10.98% with an area of 0.087 cm 2 . [15] Recently, Yao et al.

The Development of Carbon/Silicon Heterojunction Solar Cells through Interface Passivation

“…b) MXene:Nafion–Si HJ solar cell with a PCE of 14.21% at the area of 7.29 cm 2 . [ 124 ] Copyright 2022, John Wiley and Sons for Solar RRL.…”

“…Copyright 2014, Springer Nature for Nature Nanotechnology. b) MXene:Nafion-Si HJ solar cell with a PCE of 14.21% at the area of 7.29 cm 2 [124]. Copyright 2022, John Wiley and Sons for Solar RRL.…”

Passivating Contacts for Crystalline Silicon Solar Cells: An Overview of the Current Advances and Future Perspectives

“…[230,231] In a pioneering study, Fu et al [232] introduced pure MXene layers as ESCs in n-Si devices, which resulted in an efficiency of 11.5% over an area of 1.12 cm 2 . Subsequently, Zhang et al [233] employed Nafion polymer-treated MXene layers, enabling precise adjustments to the WF of MXene and achieving an efficiency of 14.72%.…”

Tuning the Work Function of MXene via Surface Functionalization

“…Currently, the reported functionalization techniques include (1) nitrogen (N) doping of MXenes using solvothermal processes or annealing MXenes under an ammonia environment to incorporate nitrogen, (2) annealing the MAX phase with ZnCl to introduce a Cl termination, (3) annealing in an inert mixture of gases to control oxidation, and (4) annealing under CO 2 to effect decomposition of the MXene structure . These terminations have recently been expanded to include other p-block elements like Se, Cl, Br, NH, etc. , Specifically, the WF of Ti 3 C 2 MXene terminated with different functional groups (Ti 3 C 2 T x ) has typically been reported to be in the range of 4.0–4.6 eV. , The density functional theory (DFT)-calculated WF lies between 1.2 and 6.2 eV for OH- and O-terminated MXene. Experimentally, through annealing at various temperatures, Schultz et al modified the surface termination to obtain a WF of around 3.9–4.8 eV.…”

“…26,27 Specifically, the WF of Ti 3 C 2 MXene terminated with different functional groups (Ti 3 C 2 T x ) has typically been reported to be in the range of 4.0−4.6 eV. 28,29 The density functional theory (DFT)-calculated 30 WF lies between 1.2 and 6.2 eV for OH-and O-terminated MXene. Experimentally, through annealing at various temperatures, Schultz et al 31 modified the surface termination to obtain a WF of around 3.9−4.8 eV.…”