X-ray Absorption Spectroscopy of Silicon Carbide Thin Films Improved by Nitrogen for All-Silicon Solar Cells

Abstract

Synchrotron-based experiments in combination with optical measurements were used to explore the potential of a photovoltaic material based on silicon carbonitride (SiCN) thin films, in particular for the use in space solar cells. The large bandgap, SiCN films were fabricated using electron cyclotron resonance plasma-enhanced chemical vapour deposition (ECR-PECVD) followed by low-temperature annealing processes. X-ray absorption near edge structure (XANES) with excitations at the carbon, nitrogen, and silicon K-edges verifies that the presence of nitrogen tends to disrupt Si–C networks. This results in the enhancement of light absorption and bandgap widening, which is desirable for front emitters in all-silicon tandem solar cells. The ternary structure of SiCN allows bandgap engineering and tuning of the light absorption and refractive index through careful design of the composition. XANES showed that the thermal annealing at a medium temperature (500 °C) using N2 ambient promoted the formation of Si–Si and C–N sp2 bonds before disappearing in higher annealing temperatures. In our opinion unlocking the potential of robust SiC mixed with nitrogen in SiCN matrix has appeal in radiation-resistant solar cells, where it can serve as the top emitter layer in all-silicon tandem solar cells and at the same time benefits the antireflection properties.

X-ray Absorption Fine Structural Study of Atomic Structures and Chemical States of Dopants in 4H-SiC(0001)

“…For the simulated XANES spectrum for N C (Figure (d)) , three main peaks are observed at 401.5, 405.4, and 420.0 eV, which is very similar to the experimental results for XANES of an N–Si structure (Figure (a)). For the simulated results, the main peak at 405.4 eV is related to π* state transitions of Si–N bond, while the peak at 420 eV is attributed to the σ* state transitions . This result is in good agreement with a previous study focused on N C sites in SiC. ,, Accordingly, we conclude that SiNx is attributed to N C .…”

“…For the simulated results, the main peak at 405.4 eV is related to π* state transitions of Si–N bond, while the peak at 420 eV is attributed to the σ* state transitions . This result is in good agreement with a previous study focused on N C sites in SiC. ,, Accordingly, we conclude that SiNx is attributed to N C .…”

“…In the 4H-SiC, all atoms in the matrix have the same valence, so the nitrogen dopant incorporation site does not affect the doping type. 51 Figures 4(c) and 4(d) show the local atomic structure and the XANES simulation for the C substitutional (N C ) site. Figures 4(e) and 4(f) show the local atomic structure and the XANES simulation for the Si substitutional (N Si ) site.…”

“…According to the previous studies based on density functional theory (DFT) calculation, the formation energy of N C is much lower than that of N Si , which is in good agreement with our results. 51,53 The N−C species (N Si ), on the other hand, acts as the electrically inactive structure, because it is predominantly formed near the surface.…”

Customized Nanostructured Ceramics via Microphase Separation 3D Printing

“…Conversely, for ceramic materials 3D printed with PLAc 103 ‐CTA, the pronounced peak at 1845 eV indicates a greater prevalence of Si‐C geometries. [ 32a,33 ] C K‐edge NEXAFS provided further structural information on the ceramic materials from the perspective of C atoms (Figure 3B). The spectra exhibited features at energies between 284.3 to 299.7 eV (Table S6, Supporting Information), which were attributed to the transitions of C 1s orbitals to σ* occur from sp 3 bonded C. [ 32,34 ] The peak fitting analysis of C K‐edge NEXAFS (Figure S21A–E, Supporting Information) revealed that the PLAc‐CTA X n plays a significant role in the formation of sp 2 bonded C atoms (284.3 eV, peak C1).…”