Hybrid Silicon-organic Solar Cell Based On PEDOT Film Prepared By Electropolymerization

As a clean and renewable green energy,solar energy is one of the effective ways to solve serious problems such as energy crisis and environmental pollution.Solar cells,which can directly convert solar energy into electrical energy,have attracted more and more attention among people.In recent years,scientists around the world show great interest in silicon/organic hybrid solar cells due to the simple organic solution process and well-established silicon?Si?processing technologies.Particularly,the conductive polymer poly?3,4-ethylenedioxythiophene??PEDOT?doped with poly?styrenesulfonate??PSS?,which has excellent conductivity and high transparency,is extensively employed for high-performance silicon hybrid solar cells.However,Si/PEDOT:PSS solar cells have poor stability because the PEDOT:PSS film exists the esay bibulous–PSS structure,which could cause the unstable performance of the prepared film and accelerate the formation of oxide layer on the silicon surface.Besides,the high acidity of PEDOT:PSS solution can easily destroy the silicon surface during preparation.Silicon nanowire arrays?SiNWs?are widely used for the high-efficiency,low-cost Si/PEDOT:PSS hybrid solar cells owing to their excellent light absorption and charge transportation.Neverthless,SiNWs are not helpful to the penetration of PEDOT:PSS solution becacuse of their dense and long wire structure.What's more,SiNWs have large specific surface area and high surface defect state density,seriously limiting the performance of SiNWs/PEDOT:PSS hybrid solar cells.In this dissertation,PEDOT film is prepared by simple and low-cost electrochemical polymerization.A series of Si/PEDOT hybrid solar cells are also fabricated and severals methods are used to improve the device stability and efficiency.The major work is as follows:?1?PEDOT film is electropolymerized on the planar silicon through a non-aqueous galvanostatic method and Si/PEDOT hybrid solar cells are firstly fabricated.The properties of PEDOT films and devices are investigated by controlling different electropolymerization time.Besides,many ways are used to improve the performance of Si/PEDOT hybrid solar cells.The experimental result shows that the efficiency of the Si/PEDOT device can attain to7.36%when optimizing the PEDOT with hydrochloroplatinic acid?H₂PtCl₆?solution.This can be ascribe that H₂PtCl₆ heated by high temperature can be decomposied into Pt nanoparticles with high work fuction.It leads to the increase in work fuction and decrease in sheet resistance of PEDOT film,both beniftcial to improve the separation and transport of the charge in the devices.Compared with the traditional Si/PEDOT:PSS hybrid solar cells,the Si/PEDOT hybrid solar cells exhibit better stability because the efficiency of Si/PEDOT hybrid solar cells still remains 90%after 10 days in air,which provides the possibility to manufacture low-cost,high-efficiency and stable Si/organic hybrid solar cells.?2?The sparseness of SiNWs are controlled by the simple and harmless physical ultrasonic treatment.After the treatment,the specific surface area and surface defect state density of the SiNWs are both reduced.However,the reflection of SiNWs is not decreased.When the ultrasonic time is 10 min,SiNWs show the best properties.Based on the optimized SiNWs,utilizing the advantage of EDOT monomer with small structure easily penetrating the bottom of nanowires,SiNWs/PEDOT hybrid solar cells are prepared and its efficiency only have 4.25%,lower than that of Si/PEDOT hybrid solar cells.The reason is the prepared PEDOT film on the surface of SiNWs have poor film formation.?3?To improve the performance of SiNWs/PEDOT hybrid solar cells,PEDOT:PSS is spin-coated on the electropolymerized PEDOT film.The experimental result shows that the efficiency of the cell can be increased to 13.1%.But the efficiency of SiNWs/PEDOT:PSS hybrid solar cells is just 10.7%.The 22.4%enhancement of efficiency can be attributed to the effectively improvement of the interface between SiNWs and the PEDOT:PSS film using the electropolymerized PEDOT film as buffer layer,which greatly reduces the series resistance of the cell.Our preliminary results provide a new method for the preparation of highly efficient and stable SiNWs hybrid solar cells.