SYNTHESIS OF LEAD SULFIDE (PbS) NANOSTRUCTURES FOR SOLAR CELL APPLICATIONS

SYNTHESIS OF LEAD SULFIDE (PbS) NANOSTRUCTURES FOR SOLAR CELL APPLICATIONS

 

ABSTRACT

 

The main aim of the research work presented in this thesis was to synthesise nanostructured PbS absorber layer for solar cell devices using simple and economical methods: chemical bath deposition (CBD), microwave assisted chemical bath deposition (MACBD) and thermal evaporation (TE). The synthesis of nanostructured PbS layers using CBD was carried out by changing Pb2+ ions source, deposition time, and molar concentration. The results showed that the morphology and size-scale of nanostructured PbS features are highly dependent on each parameter. X-ray diffraction analysis (XRD) analysis revealed that all nanostructured PbS thin films exhibit a cubic rock salt (NaCl) type structure. The optimal condition to synthesise nanostructured PbS using CBD was lead nitrate as Pb2+ ions source with 0.1M molar concentration. The PbS sample with optimum conditions was selected to be used as an absorber layer on the PbS/CdS/ITO solar cell device.

After that, nanostructured PbS was deposited by MACBD under different conditions: changing Pb2+ ion source, varying the deposition time in the range of 30 up to 90 min, and changing the molar concentration. Scanning electron microscopy (SEM) analysis shows that each parameter has effect on morphology changes. Crystal structure analysis by XRD confirms the formation of single cubic phase with rock salt (NaCl) type structure. The lattice constants and the crystallite size were observed to be sensitive to the variation of experimental parameters. PbS thin films obtained under optimum conditions using lead nitrate as Pb2+ ions source, a deposition time of 30 min with molar concentration in the range of 0.025 - 0.1 M were selected to fabricate PbS/CdS/ITO solar cell device. PbS/CdS/ITO solar cell device at 0.1 M molar concentration possesses the highest conversion efficiency of 1.68% compared to 0.35%, 0.98%, and 1.28%, at molar concentration of 0.025, 0.05, and 0.075 M, respectively.

Finally, PbS nanostructures were prepared by TE by changing deposition temperature, distance between powder and substrates, and different substrates. SEM analysis shows that the morphology was greatly affected by the above parameters. All nanostructured PbS thin films crystallizes within a cubic rock salt (NaCl) type structure as confirmed by XRD analysis. The lattice parameter and the crystallite size were found to be very sensitive with experimental parameters. The result show that the optimum conditions, a growth temperature of 1050°C and a distance of 15 cm with different substrates led to produce various nanostructures. The obtained nanocoral PbS was used to fabricate PbS/ITO Schottky solar cell and gives an efficiency of 0.89%.

 molar concentration possesses the highest conversion efficiency of 1.68% compared to 0.35%, 0.98%, and 1.28%, at molar concentration of 0.025, 0.05, and 0.075 M, respectively.

Finally, PbS nanostructures were prepared by TE by changing deposition temperature, distance between powder and substrates, and different substrates. SEM analysis shows that the morphology was greatly affected by the above parameters. All nanostructured PbS thin films crystallizes within a cubic rock salt (NaCl) type structure as confirmed by XRD analysis. The lattice parameter and the crystallite size were found to be very sensitive with experimental parameters. The result show that the optimum conditions, a growth temperature of 1050°C and a distance of 15 cm with different substrates led to produce various nanostructures. The obtained nanocoral PbS was used to fabricate PbS/ITO Schottky solar cell and gives an efficiency of 0.89%.

 

SINTESIS STRUKTUR NANO PLUMBUM SULFIDA (PbS) BAGI APLIKASI SEL SOLAR

 

ABSTRAK

 

Tujuan utama kerja-kerja penyelidikan yang dibentangkan dalam tesis ini adalah untuk mensintesiskan lapisan penyerap PbS berstruktur nano untuk peranti sel solar menggunakan kaedah yang mudah dan ekonomi: pemendapan rendaman kimia (CBD), pemendapan rendaman kimia berbantukan gelombang mikro (MACBD) dan penyejatan terma (TE). Sintesis lapisan PbS berstruktur nano menggunakan CBD telah dijalankan dengan menukar sumber ion Pb2+, masa pemendapan, dan kepekatan molar. Hasil kajian menunjukkan bahawa ciri-ciri morfologi dan skala saiz PbS berstruktur nano sangat bergantung pada setiap parameter. Analisis pembelauan sinar-x (XRD) mendedahkan bahawa filem nipis PbS berstruktur nano mempamerkan struktur jenis garam batuan kubus (NaCl). Keadaan optimum untuk sintesis PbS berstruktur nano menggunakan CBD adalah plumbum nitrat sebagai sumber ion Pb2+ dengan kepekatan molar 0.1 M. Sampel PbS dengan keadaan optimum telah dipilih untuk digunakan sebagai lapisan penyerap pada peranti sel solar PbS / CdS / ITO.

Selepas itu, PbS berstruktur nano dimendapkan menggunakan MACBD di bawah keadaan yang berbeza: mengubah sumber ion Pb2+, mengubahkan masa pemendapan dalam lingkungan 30 hingga 90 minit, dan kepekatan molar. Analisis mikroskopi imbasan elektron (SEM) menunjukkan bahawa setiap parameter mempunyai kesan ke atas perubahan morfologi. Analisis struktur hablur oleh XRD mengesahkan pembentukan fasa tunggal kubik dengan jenis garam batu (NaCl). Pemalar kekisi dan saiz hablur didapati adalah sensitif kepada perubahan parameter eksperimen. Filem nipis PbS yang diperolehi di bawah syarat-syarat yang optimum menggunakan plumbum nitrat sebagai sumber ion Pb2+, masa pemendapan 30 min dengan kepekatan molar dalam lingkungan 0.025-0.1 M telah dipilih untuk mengfabrikasikan peranti sel solar PbS/CdS/ ITO. Peranti sel solar PbS/CdS/ ITO pada kepekatan molar 0.1 M mempunyai kecekapan penukaran tertinggi sebanyak 1.68% berbanding 0.35%, 0.98% dan 1.28%, pada kepekatan molar 0.025, 0.05, dan 0.075 M, masing-masing.

Akhirnya, struktur nano PbS telah disediakan oleh TE dengan menukar suhu pemendapan, jarak antara serbuk dan substrat, dan substrat yang berbeza. Analisis SEM menunjukkan morfologi adalah sangat dipengaruhi oleh parameter di atas. Filem nipis PbS berstruktur nano menghablur dalam struktur jenis garam batuan kubus (NaCl). seperti yang disahkan oleh analisis XRD. Parameter kekisi dan saiz hablur telah didapati sangat sensitif dengan parameter eksperimen. Keputusan menunjukkan bahawa syarat-syarat yang optimum, suhu pertumbuhan 1050°C dan jarak 15 cm dengan substrat yang berbeza membawa kepada menghasilkan pelbagai struktur nano. Terumbu karang nano PbS telah digunakan untuk mengfabrikasikan sel solar Schottky PbS/ITO dan memberikan kecekapan sebanyak 0.89%.