| Solar cell is a photoelectric device that converts solar energy into electricity.Based on the application requirements,the development of new materials and devices with high efficiency and low cost is a cutting-edge and challenging topic in the field of photovoltaic energy.Antimony sulfide(Sb2S3)is a kind of V-VI direct band gap semiconductor material with abundent elements and non toxicity.Sb2S3 is promising light absorption material for solar cells thanks to its merits of tunable band gap,high carrier mobility,large light absorption coefficient and high stability.This dissertation aims to develop the solution-processing approaches to prepare Sb2S3 micro/nanoparticle films and to investigate the correlation between the structural characteristics and photovoltaic performance and the related principles involved in solar cells.The main activities and results in this dissertation are summarized as follows:(1)An in-situ solution-processing method is developed to prepare Sb2S3 nanoparticle film,and the correlation between the composition and photovoltaic performance in the film is investigated.The Sb2S3 nanoparticle film with a certain degree of[221]orientation is prepared on the surface of TiO2 nanoparticle films by using a new Sb2S3 precursor solution and a simple one-step spin-coating/annealing method,providing a high-quality Sb2S3/TiO2 planar heterojunction film.Using the heterojunction film as photoactive layer and Spiro-OMeTAD film as the hole transport material(HTM),a planar heterojunction thin film solar cell with FTO/TiO2/Sb2S3/HTM/Au structure is prepared.Under AM 1.5G(100 mW/cm2)standard illumination,the power conversion efficiency of the solar cell reaches 5.74%,which is the highest efficiency amongst similarly prepared solar cells.Results show that the crystallinity,crystal orientation and trap density of Sb2S3 nanoparticle film depends strongly on the S/Sb molar ratio in the precursor solution;when the S/Sb molar ratio is 1.8,the resulting Sb2S3 nanoparticle film has the composition very close to stoichiometric ratio,the lowest defect density and the highest crystallinity,leading to the smallest charge recombination and the peak efficiency in the solar cell.In addition,the thickness of Sb2S3 nanoparticle film is linearly dependent on the precursor concentration,but it is not affected by the molar ratio of S/Sb in the precursor solution.This study provides a new method to prepare solution-processed quality Sb2S3 nanoparticle films and solar cells.(2)A method to improve the performance of Spiro-OMeTAD HTM by adding amorphous conjugated polymer is developed.A new Spiro-OMeTAD:MEH-PPV composite hole transport material is obtained by adding a small amount of amorphous polymer MEH-PPV to the traditional Spiro-OMeTAD-based HTM,and a planar heterojunction thin film solar cell structured as FTO/TiO2/Sb2S3/HTM/Au is prepared.Under AM 1.5G(100 mW/cm2)standard illumination,the efficiency of the solar cell is improved to 6.02%.Results show that the MEH-PPV doping improves the quality of the HTM layer by suppressing the pinhole formation and the trap density therein,which significantly reduces the charge recombination and further increases the charge collection efficiency in the device,consequently leading to an effectively improved the device efficiency;at the same time,the MEH-PPV doping significantly improves the hydrophobicity of the hole transport layer and effectively improves the long-term stability of the solar cell.This study provides a new strategy for improving the quality of Spiro-OMeTAD-based hole transport layer.(3)A parallel planar heterojunction strategy based on Sb2S3 and perovskite double absorption layer is developed.With depositing a PVK thin film as an secondary absorbent layer onto Sb2S3/TiO2 bulk/nano heterojunction film,a novel new parallellystructured Sb2S3 solar cell is fabricated,which features Sb2S3-based sub-devices(structured as FTO/TiO2/Sb2S3/PVK/HTM/Au)paralleled by PVK-based sub-devices(structured as FTO/TiO2/PVK/HTM/Au).Under the AM 1.5G(100 mW/cm2)standard simulated illumination,the Sb2S3 solar cell delivers an efficiency of 8.32%,which is the highest efficiency amongst Sb2S3 solar cells.Results show that PVK infiltrates into gaps between the Sb2S3 single-crystalline bulk grains and forms a uniform film over the Sb2S3 layer,and the parallelly-structured solar cell originates from the Sb2S3 bulk grains and the infiltrated PVK phases.The existence of PVK-based auxiliary sub-devices significantly boosts the performance of Sb2S3 solar cell mainly by reducing the chagre recombination,promoting the transportation of charge carriers and consequently increasing the charge collection efficiency in the divice.This study provides a new idea for improving the performance of Sb2S3 solar cells. |
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