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Title:	New approach in semiconductor��electrolyte junction of solid-state dye��sensitized solar cell
Authors:	Mohd Sukor Su��ait (P59408)
Supervisor:	Azizan Ahmad, Assoc. Prof. Dr.
Keywords:	Dye-sensitized solar cell (DSSC) Semiconductor-electrolyte Solid polymer electrolyte Dissertations, Academic -- Malaysia Universiti Kebangsaan Malaysia -- Dissertations
Issue Date:	20-Aug-2014
Description:	An alternative to the conventional design of dye-sensitized solar cell (DSSC) is proposed, based on interface modification of semiconductor-electrolyte junction. A solid-state DSSC was developed by combining bio-based polyurethane (PU) polymer electrolyte from palm kernel oil monoester-OH (PKO-p) and kesterite, (Cu2ZnSnS4), a promising low-cost inorganic material for absorbing layer. The PU pre-polymer solution was prepared via pre-polymerization technique by reacting PKO��p and 2,4��methylene diphenyl diisocyanate in acetone under nitrogen gas atmosphere at room temperature. The PU based electrolyte films were prepared by adding lithium iodide (LiI) salt at different weight percentage (wt.%) using solution casting technique. On the other hand, the Cu2(Zn1-x,Fex)SnS4 precursors were prepared by a high energy planetary milling technique and annealed at 550 �C for 2 h in the presence of sulphur atmosphere. The formation of urethane linkages (NHCO backbone) after the polymerization was confirmed by the disappearance of N=C=O peak and the appearance of amine (secondary), carbonyl, carbamate, ether, and ester groups in the PU chain. The weight average molecular mass increased with increasing polyol ratio up to 1.23 × 106 g mol-1. Nevertheless, at higher content of PKO-p resulted in a low crosslink PU with only 4% of crosslink and poor physical properties such as soft, sticky and easy to tear which is influenced by the non-hydrogen bonded urethane. The glass transition temperature decreased from 67 �C to 30 �C with increasing PKO-p content. Although all samples experienced the same thermal stability at 187 �C, but there was a significant difference observed in the mass loss for all NCO/OH ratios. The pure PU at various NCO/OH ratios gave bulk resistant up to 107-105 Ω. Upon addition of LiI salt, the ionic conductivity increased to the highest value of 7.46 × 10-4 S cm��1 at 25 wt.% LiI salt. The chemical interaction between segmented PU and Li+ from LiI salt has been confirmed by infrared spectroscopy. The thermal studies carried out by thermogravimetry analysis have proven the occurrence of polymer-salt complexation. The structural analysis by X-ray diffraction (XRD) has revealed that PU with 25 wt.% LiI reduced the semi-crystalline characteristics of pure PU. The temperature dependence of conductivity of the PU based electrolyte obeyed the Arrhenius law with the pre-exponential factor, σo of 2.41 × 10��3 S cm��1 and activation energy, Ea of 0.11 eV. Whereas, the characterization of Cu2(Zn1-x,Fex)SnS4 crystal powders by in-situ high temperature synchrotron radiation XRD revealed transformation of iron from metallic state to the alloying in the final Cu2ZnSnS4 crystal structure. The oxidation state of iron studied by XPS showed no traces of metallic iron in the final phase of Cu2ZnSnS4 crystal. This observation was consistent with energy-dispersive X-ray spectroscopy (EDAX) microanalysis results. Current-voltage measurement of FTO/TiO2-Cu2ZnSnS4-dye/liquid electrolytes/Pt indicated that a low Cu2ZnSnS4 concentration, 0.30 mM produced the highest power conversion efficiency under light intensity of 100 mW cm��2 up to 4.75%. A DSSC of FTO/TiO2-dye/PU-LiI:I2/Pt demonstrated a photovoltaic response with efficiency of 0.004 %. The combination of bio-based PU-LiI:I2 and Cu2ZnSnS4 in DSSC has successfully increased the efficiency of solid-state PU polymer electrolyte based DSSC up to 40 % with a power conversion efficiency at 0.15% give Jsc of 1.30 m Acm��2 and Voc of 0.35 V. These results revealed that the bio-based PU solid polymer electrolyte and Cu2ZnSnS4 photovoltaic material has the potential to be used for DSSC components.,Alternatif kepada reka bentuk konvensional sel suria terpeka pewarna (DSSC) dikemukakan berdasarkan pengubahsuaian antara muka pada persimpangan semikonduktor-elektrolit. DSSC keadaan pepejal telah dibangunkan dengan menggabungkan elektrolit polimer berasaskan bio poliuretana (PU) dari monoester-OH minyak isirung sawit (PKO-p) dan kesterit (Cu2ZnSnS4) sebagai lapisan penyerap bukan organik berkos rendah. Larutan pra-polimer PU disediakan melalui teknik pra-pempolimeran dengan menindakbalaskan PKO��p dan 2,4��difenil metilena diisosianat di dalam aseton di bawah persekitaran gas nitrogen pada suhu bilik. Filem elektrolit berasaskan PU disediakan dengan penambahan garam litium iodida (LiI) pada peratus jisim (wt.%) yang berbeza menggunakan teknik penuangan larutan. Sebaliknya, prekursor Cu2(Zn1-x,Fex)SnS4 disediakan dengan teknik pengisaran planet bertenaga tinggi dan disepuhlindap pada suhu 550 �C selama dua jam dengan kehadiran persekitaran sulfur. Pembentukan jaringan uretana (rantai utama NHCO) selepas pempolimeran dibuktikan dengan kehilangan puncak N=C=O dan kemunculan puncak kumpulan amina (sekunder), karbonil, karbamat, eter dan ester dalam rantai PU. Purata berat jisim molekul meningkat dengan pertambahan nisbah poliol sehingga mencapai 1.23 × 106 g mol-1. Namun begitu, kandungan PKO-p yang tinggi mengakibatkan tautsilang PU yang rendah dengan hanya 4 % tautsilang dan sifat fizikal yang lemah seperti lembut, melekit dan mudah koyak yang mana dipengaruhi oleh rantai uretana yang tidak terikat dengan ikatan hidrogen. Suhu peralihan kaca didapati berkurang dari 67 �C ke 30 �C dengan peningkatan kandungan PKO-p. Walaupun semua sampel mengalami kestabilan terma yang sama pada 187 �C tetapi terdapat perbezaan ketara pada kehilangan jisim untuk semua nisbah NCO/OH. PU tulen pada nisbah NCO/OH yang berbeza memberikan nilai kerintangan pukal sekitar 107-105 Ω. Selepas penambahan garam LiI, kekonduksian ion meningkat sehingga 7.46 × 10-4 S cm��1 pada 25 wt.% garam LiI. Interaksi kimia di antara segmen PU dan Li+ dari garam LiI dibuktikan dengan analisis spektroskopi inframerah. Kajian terma dijalankan oleh analisis termogravimetri membuktikan berlakunya kompleks polimer-garam. Analisis struktur oleh pembelau sinar-X (XRD) mendapati PU dengan 25 wt.% garam LiI mengurangkan ciri-ciri semi-hablur PU tulen. Kebergantungan suhu pada kekonduksian ion bagi elektrolit berasaskan PU didapati mematuhi hukum Arrhenius dengan faktor pra-eksponen, σo = 2.41 × 10��3 S cm��1 dan tenaga pengaktifan, Ea = 0.11 eV. Manakala, pencirian hablur Cu2(Zn1-x,Fex)SnS4 menggunakan XRD dengan sinar sinkrotron secara langsung (in-situ) pada suhu tinggi mendapati ferum berubah daripada keadaan logam kepada mengaloi pada struktur akhir hablur Cu2ZnSnS4. Nombor pengoksidaan ferum dikaji menggunakan XPS menunjukkan tiada kesan logam ferum pada fasa akhir hablur Cu2ZnSnS4. Pemerhatian ini adalah konsisten dengan keputusan mikroanalisis menggunakan spektroskopi tenaga-serakan sinar-X (EDAX). Pengukuran arus-voltan FTO/TiO2-Cu2ZnSnS4-pewarna/elektrolit cecair/Pt mendapati pada kepekatan Cu2ZnSnS4 yang rendah, 0.30 mM memberikan kecekapan penukaran tenaga (η) yang tertinggi di bawah keamatan cahaya 100 mW cm��2 sehingga 4.75%. DSSC FTO/TiO2-pewarna/PU-LiI:I2/Pt memberikan respons fotovoltaik dengan kecekapan 0.004%. Gabungan PU-LiI:I2 dan Cu2ZnSnS4 ke dalam DSSC berjaya meningkatkan kecekapan sehingga 40% dengan kecekapan pada 0.15% memberikan Jsc = 1.30 mA cm��2 dan Voc = 0.35 V. Keputusan ini menunjukan elektrolit polimer pepejal berasakan bio PU dan bahan fotovoltaik Cu2ZnSnS4 berpotensi digunakan sebagai komponen DSSC.,Ph.D.
Pages:	175
Call Number:	QC611.6.J85.M837 2014 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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