Effects of the PbBr2:PbI2 Molar Ratio on the Formation of Lead Halide Thin Films, and the Ratio’s Application for High Performance and Wide Bandgap Solar Cells

Materials

Hyunseung Lee¹  Son Singh²  Jae-Hun Kim²  Jaegab Lee²  Ho-Seok Nam²  Md. Abdul Kuddus Sheikh²  Rahim Abdur²  Sung-Min Lee² 

[1] Department of Fashion Industry, Incheon National University, Incheon 22012, Korea;School of Advanced Materials Engineering, Kookmin University, Seoul 02707, Korea;

关键词: mixed lead halide;    surface morphology;    microstructure;    solar cells;    performance;    stability;   

DOI  :  10.3390/ma15030837

来源: DOAJ

【 摘 要 】

We investigate the effects of the molar ratio (x) of PbBr₂ on the phases, microstructure, surface morphology, optical properties, and structural defects of mixed lead halides PbI_2(1−x)Br_2x for use in solar cell devices. Results indicate that as x increased to 0.3, the surface morphology continued to improve, accompanied by the growth of PbI₂ grains. This resulted in lead halide films with a very smooth and continuous morphology, including large grains when the film was formed at x = 0.3. In addition, the microstructure changed from (001)-oriented pure PbI₂ to a highly (001)-oriented β (PbI₂-rich) phase. The plausible mechanism for the enhanced morphology of the lead halide films by the addition of PbBr₂ is proposed based on the growth of a Br-saturated lead iodide solid solution. Furthermore, iodine vacancies, identified by X-ray photoelectron spectroscopy, decreased as the ratio of PbBr₂ increased. Finally, an electrical analysis of the solar cells was performed by using a PN heterojunction model, revealing that structural defects, such as iodine vacancies and grain boundaries, are the main contributors to the degradation of the performance of pure PbI₂-based solar cells (including high leakage, low stability, and high hysteresis), which was significantly improved by the addition of PbBr₂. The solar cell fabricated at x = 0.3 in air showed excellent stability and performance. The device lost merely 20% of the initial efficiency of 4.11% after 1500 h without encapsulation. This may be due to the dense microstructure and the reduced structural defects of lead halides formed at x = 0.3.

【 授权许可】

Unknown