研究目的
To study the effect of selenisation temperature on photoluminescence and photoluminescence excitation spectra of ZnO/CdS/Cu2ZnSnSe4/Mo/glass solar cells, and understand the changes in electronic properties due to solar cell processing.
研究成果
Solar cell processing increases PL intensity and causes blue shifts in the dominant P1 band, with the strongest effects at 500°C selenisation. This is attributed to reduced non-radiative recombination centers and inter-diffusion of elements forming new donors (e.g., CdCu), which depends on film composition. The recombination mechanism remains free-to-bound, but compensation degree increases, indicating changes in defect chemistry. Bandgaps and potential fluctuations are affected variably by processing.
研究不足
The study is limited to optical characterization; electrical measurements could not be performed on all samples due to issues like complete selenisation of Mo back contact. The influence of the p-n junction on PL spectra might not be fully significant under high excitation conditions. The exact nature of each processing effect (e.g., etching vs. inter-diffusion) is difficult to isolate.
1：Experimental Design and Method Selection:
The study involves fabricating CZTSe thin films by selenising metallic precursors at different temperatures (450°C, 500°C, 550°C), followed by solar cell processing including KCN etching, CdS deposition via chemical bath deposition, and ZnO/ZnO:Al deposition via DC-magnetron sputtering. Photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy are used to analyze optical properties at low temperatures (4.2 K to 300 K).
2：2 K to 300 K).
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Samples are CZTSe films on Mo/glass substrates, with elemental compositions determined by wavelength dispersive X-ray microanalysis. Data includes PL and PLE spectra measured under controlled conditions.
3：List of Experimental Equipment and Materials:
Equipment includes a single grating monochromator, Ar+ laser (514 nm line), closed-cycle helium cryostat, InGaAs photomultiplier tube (PMT), liquid helium bath cryostat, halogen tungsten lamp, and InGaAs photodiode. Materials include high-purity Cu, Zn, Sn targets, Se pellets, KCN solution, CdS, ZnO, and Mo/glass substrates.
4：Experimental Procedures and Operational Workflow:
Precursors are sputtered and selenised in a rapid thermal processor. Films are etched with KCN, CdS is deposited via CBD, and ZnO layers are sputtered. PL and PLE measurements are conducted at various temperatures and excitation intensities, with spectra analyzed using fitting functions.
5：Data Analysis Methods:
PL spectra are fitted with asymmetric double sigmoidal functions to determine parameters like bandgap, potential fluctuations depth, and activation energies. Excitation intensity and temperature dependencies are analyzed to identify recombination mechanisms.
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