Interface Engineering Of Silver Sulfide Thin Film Solar Cells

The low cost and high efficiency of thin film solar cells are an important research direction of wearable power supply devices.Narrow band-gap metal sulfide semiconductors have attracted considerable interest owing to their tunable band gap(Eg),low cost fabrication and excellent photoelectric characteristics.With a direct band-gap(Eg=0.9?1.1 eV),large absorption coefficient and excellent chemical stability,environmentally friendly Ag2S has been used in solar cells as an absorber layer,which can reach PCE of 30%in theory.At present,the efficiency of thin film solar cells based on Ag2S is still not high.Therefore,it is a huge challenge to improve the performance of thin film solar cells,which also is the main research content of this paper.Based on the Ag2S thin film material prepared at room temperature,we assembled the eco-friendly Ag2S thin film solar cell device,and optimized the interface between Ag2S and the substrate as well as the hole transport layer to continuously improve the photoelectric conversion efficiency of the solar cell.It was found that the formation of Schottky barrier at the interface between FTO and Ag2S could cause the recombination of photoinduced charge carriers,which can affect the PCE of solar cells.To solve the problem,CdS was employed as a bottom layer to adjust the Fermi level of the FTO and reduce the recombination of photoinduced charge carriers at the Ag2S/FTO interface.Transient surface photovoltage(TSPV)and other tests show that the photogenerated carrier recombination between the modified FTO and Ag2S film can effectively inhibit the PCE by about 52%.In the aspect of hole transport,the matching problem of hole transport between Ag2S material and hole transport layer is studied.The low hole mobility of organic semiconductor materials can affect the PCE of solar cells.The additive FK209 and Spiro(TFSI)2 were introduced into the hole transport layer.Compared with the conventional Spiro-OMeTAD material,the introduction of FK209 or Spiro(TFSI)2 improved the conductivity of the hole transport layer and inhibited the recombination of photoinduced charge carriers in the Ag2S/Spiro-OMeTAD hybrid films.Finally,when the added concentration of FK209 was 1.3 mol%,the average efficiency of the device was increased by 34.6%,and the optimal efficiency was increased by about 30%from the original 1.76%to 2.29%.When the added concentration of Spiro(TFSI)2 was 3 mol%,the average efficiency of the device increased by 40%,and the optimal efficiency increased to 2.56%.The innovation of this paper is mainly manifested in the following three aspects:(1)The charg carrier recombination between Ag2S and FTO substrate is regulated to improve the photoelectric conversion performance of the device;(2)Using transient surface photovoltage(TSPV)technique,the dynamic process of photogenerated carrier in Ag2S heterojunction films was studied;(3)FK209 and Spiro(TFSI)2 were introduced into the Ag2S solar cell system to improve the hole migration rate,reduce the recombination of photogenerated carriers and improve the device performance.