Study On The Odification Of Electron Transport Layer For Sb₂S₃ Solar Cells

Antimony sulfide（Sb₂S₃）is an attractive solar absorber material that has attracted tremendous interest due to its fascinating properties for solar cells including suitable band gap,high absorption coefficient,earth abundance,and excellent stability etc.However,power conversion efficiency（PCE）of Sb₂S₃-based solar cells still much lower than the theoretically predicted value due to the imperfect energy level alignment at the charge transport layer/Sb₂S₃interfaces thus leading to severe charge recombination.In the past few years,intensive efforts have been made to enhance the photovoltaic efficiencies of Sb₂S₃solar cells using many promising approaches including interfacial engineering,surface passivation,additive engineering,and band-gap engineering of the charge transport layers and active light absorbing Sb₂S₃materials.Electron transport layer is a very crucial factor to the performances of Sb₂S₃solar cells.The main research work of this thesis is to modify or replace the electron transport layer（ETL）of Sb₂S₃solar cells to improve the quality of Sb₂S₃film and the PCE of Sb₂S₃solar cells.The main contents of this thesis are listed below:1.Nanostructured CdS thin films are fabricated by a simple spin-coating method at various annealing temperatures from 200℃to 350℃.CdS films of 80 nm thick,which are composed of nanoparticles or flakes with size≈20-200 nm,are obtained.The nanostructured morphology is identified by scanning electron microscopy measurement.Sb₂S₃films with large-sized grains are deposited on the CdS thin films with hydrothermal method,in which CdS is adopted as ETL for Sb₂S₃solar cells.The PCE is 4.88%for the best solar cell based on the nanostructured CdS ETLs.2.TiO₂ is commonly used as ETLs for Sb₂S₃solar cells.Since its poor compatibility,CdS is usually adopted as buffer layer（BL）to enhance the performance.Herein,we prepared TiO₂ ETL with a commonly spin-coating method first,and then we deposited CdS on the TiO₂ ETL with a facile spin coating method to construct TiO₂/CdS double ETLs.The spin coating processed CdS is found to exhibit flake morphology,which improved the electronic properties of TiO₂ and the grain morphology of Sb₂S₃films.The CdS BLs by spin coating process were found to afford a unique pathway for electron transport thus enhancing electron extraction.As a result,large short circuit current density(J_sc)was obtained in the Sb₂S₃solar cells on the CdS buffered ETL.A champion PCE of 5.59%was obtained.3.Comparing with some oxides,CdS exhibits excellent compatibility to Sb₂S₃ therefore is most commonly used as buffer layer materials for Sb₂S₃solar cells.Proper passivation can enhance the performance of CdS BL thus raising the performances of Sb₂S₃solar cells.Herein,we put forward a self-passivation strategy to enhance the performance of CdS by a two-step deposition process to fabricate the self-passivated CdS BL.First,we adopted spin coating combined with annealing process to prepare flaked CdS on FTO,then we performed passivation process to the CdS by depositing another layer of CdS with chemical bath deposition（CBD）method.After Sb₂S₃were deposited on the self-passivated CdS by hydrothermal method,a solar cell of structure FTO/CdS/Sb₂S₃/Spiro-OMe TAD/Ag was produced.Comparing with the single spin coating processed CdS or single chemical bath deposited CdS BL,the self-passivated CdS presents better performance.The CBD process presents distinctive passivation effects to the first layer.In consequence,we obtained the highest PCE of 6.04%in the Sb₂S₃ solar cells on the self-passivated CdS BL.