Cerous Fluoride Dopant‐Free Electron‐Selective Contact for Crystalline Silicon Solar Cells

Abstract

Dopant‐free carrier‐selective contacts have drawn intensive attention for efficient crystalline silicon (c‐Si) photovoltaics due to the low‐temperature simple process and better carrier selectivity. By incorporating a thermally evaporated dielectric film cerium fluoride (CeF3) as the electron transport layer (ETL) between a c‐Si(n) and aluminum (Al) electrode, higher conversion efficiency of the crystalline silicon solar cell is obtained, which is 21.27% compared to 16.89% of a reference cell without CeF3. The insertion of an ultrathin CeF3 ETL helps in alleviating the strong Fermi‐level pinning at the interface, leading to better electron transport with a low contact resistivity of 10.96 mΩ cm2. The morphology and element distribution of the interface are also investigated by high‐resolution transmission electron microscopy (HRTEM). The primary results demonstrate that the utilization of kinds of lanthanide fluorides, including CeF3, offers a good choice for efficient and cost‐effective electron‐selective contacts for optical–electrical devices.

A High-Quality Dopant-Free Electron-Selective Passivating Contact Made from Ultra-Low Concentration Water Solution

“…The test structure of TLM is shown in Figure 2 b. A champion ρ c value of 0.31 mΩ·cm 2 is achieved, lower than most reported structures [ 17 , 18 , 19 , 39 ]. The contact resistance increases significantly once the optimal concentration (~4 mg/mL) deviates as shown in Figure 2 c.…”

“…In addition, these materials can be easily deposited by thermal evaporation. As for dopant-free electron-selective contacts, halides of alkaline (earth) metals and rare earth metals such as LiF x [ 13 , 14 ], CsF x [ 15 ], MgF x [ 16 ], CeF x [ 17 ], and GdF x [ 18 ] are the most intensively investigated system. Contact resistivity as low as ~1 mΩ·cm 2 has been reported [ 19 ].…”

Gadolinium Fluoride as a High-Thickness-Tolerant Electron-Selective Contact Material for Solar Cells

“…The GdF 3 /Al stack was applied as the dopant-free electron-selective contact to n-Si solar cells with a partial rear contact architecture. This architecture can make full use of the extremely low contact resistivity and partially overcome the shortage of the poor surface passivation effect of thermally evaporated films 48 (Figure S1). The schematic of fabricated proof-of-concept 2 × 2 cm 2 cells is shown in Figure 4a.…”

Carrier‐selective contacts using metal compounds for crystalline silicon solar cells

“…This can be largely attributed to the fact that silicon-based contacts are much further along the learning curve, with billions of cells processed, enabling more F I G U R E 3 Literature overview of cell V oc , FF and efficiency values. The comparison includes reference contacts based on doped-silicon, [12][13][14][15][16][17][18][19][20] hole-selective metal compound contacts, 9,[21][22][23][24][25][26] electron-selective metal compound contacts, 8,[27][28][29][30][31][32][33][34][35][36][37][38][39][40] and fully dopant-free solar cells. [41][42][43][44][45] The contour plot shows the ideal cell efficiency assuming a J sc of 43.31 mA/cm 2 , which corresponds to the idealised J sc of the 110 μm-thick c-Si solar cell as modelled by Richter et al 46 This ideal solar cell with a 29.43% efficiency is indicated by the star symbol.…”