Hydrothermal Synthesis Of Nitrogen And Phosphorus Co-Doped Carbon Dots From Enset For An Interfacial Modification Layer Of Zno ETL In PTB7:PC70BM Bulk Heterojunction Polymer Solar Cell

Abstract

The interface between the active layer and charge transporting layer is critical and plays an important role in performance improvement in polymer solar cells (PSCs). In this thesis, the focus is to improve the performance of inverted PTB7:PC70BM-based polymer solar cells through interfacial modification between ZnO and the active layer. Zinc oxide (ZnO) is a common Electron Transport Layer (ETL) used in PSCs, but its use in highly efficient PSCs including those based on PTB7:PC70BM, is limited due to numerous surface defects, mismatched energy bands with the photoactive layer, and incompatibility between the active layer and ZnO ETL. Herein, Nitrogen and Phosphorus co-doped Carbon Dots (N- & P- CDs) was synthesized from enset (Ensete ventricosum) as a main precursor, ethylenediamine as a nitrogen dopant precursor, and orthophosphoric acid as a phosphorus dopant precursor using hydrothermal synthesis method for interfacial modification in ETL for an inverted PTB7:PC70BM based PSC. The N & P-CDs films were characterized using XRD, FTIR, SEM, UV-Vis Absorption, PL, Transmittance, CV, and EIS. The synthesized N- & P- CDs show absorbance in UV range, and exhibited excitation wavelength dependent photoluminescence, as well as down-shifting higher-energy UV light to lower-energy visible light, and emitted bright blue light when illuminated with a 365 nm lamp. The synthesized N- & P- CDs were employed as an interfacial modification layer for the ZnO ETL with device structure of Glass/ITO/ZnO/N- & P- CDs/PC70BM:PTB7/MoO3/Al, and show more than 31 % performance improvement compared to a device without interfacial modification layer. This is due to the improvement of charge extraction efficiency by smoothing ZnO surface defects and minimizing band mismatch between the active layer and ZnO using N- & P- CDs. The results indicate that the water-soluble N- & P- CDs developed in this study have the potential to be used in solution-processable large-area PSCs.The Interface Between The Active Layer And Charge Transporting Layer Is Critical And Plays An Important Role In Performance Improvement In Polymer Solar Cells (Pscs). In This Thesis, The Focus Is To Improve The Performance Of Inverted Ptb7:Pc70bm-Based Polymer Solar Cells Through Interfacial Modification Between Zno And The Active Layer. Zinc Oxide (Zno) Is A Common Electron Transport Layer (Etl) Used In Pscs, But Its Use In Highly Efficient Pscs Including Those Based On Ptb7:Pc70bm, Is Limited Due To Numerous Surface Defects, Mismatched Energy Bands With The Photoactive Layer, And Incompatibility Between The Active Layer And Zno Etl. Herein, Nitrogen And Phosphorus Co-Doped Carbon Dots (N- & P- Cds) Was Synthesized From Enset (Ensete Ventricosum) As A Main Precursor, Ethylenediamine As A Nitrogen Dopant Precursor, And Orthophosphoric Acid As A Phosphorus Dopant Precursor Using Hydrothermal Synthesis Method For Interfacial Modification In Etl For An Inverted Ptb7:Pc70bm Based Psc. The N & P-Cds Films Were Characterized Using Xrd, Ftir, Sem, Uv-Vis Absorption, Pl, Transmittance, Cv, And Eis. The Synthesized N- & P- Cds Show Absorbance In Uv Range, And Exhibited Excitation Wavelength Dependent Photoluminescence, As Well As Down-Shifting Higher-Energy Uv Light To Lower-Energy Visible Light, And Emitted Bright Blue Light When Illuminated With A 365 Nm Lamp. The Synthesized N- & P- Cds Were Employed As An Interfacial Modification Layer For The Zno ?Etl With Device Structure Of Glass/Ito/Zno/N- & P- Cds/Pc70bm:ptb7/Moo3/Al, And Show More Than 31 % Performance Improvement Compared To A Device Without Interfacial Modification Layer. This Is Due To The Improvement Of Charge Extraction Efficiency By Smoothing Zno Surface Defects And Minimizing Band Mismatch Between The Active Layer And Zno Using N- & P- Cds. The Results Indicate That The Water-Soluble N- & P- Cds Developed In This Study Have The Potential To Be Used In Solution-Processable Large-Area Pscs.