Study Of The Interface Construction And Photoelectric Properties Of Stacking Photovoltics

In recent years,perovskite thin film solar cells(PSCs)have become the research frontier in the field of photovoltaics.The power conversion efficiency (PCE) of PSCs has increased from 9.7% in 2012 to over 24% at present.Development of novel structures is of great significance for advancing the industrialization of PSCs and enriching our understanding of PSCs' s photo-electric physical properties.Stacking PSCs(S-PSCs)is a new structure by comparison to other PSCs.First,it can be assembled by stacking two independent electrodes(photoanode and back electrode)together under external mechanical stress,which is suitable for roll-to-roll and modular production.Second,noble metal electrode(such as Ag and Au)fabricated through high vacuum evaporation is not needed,favorable to reducing production cost.Third,the device structure can be flexibly assembled and disassembled repeatedly.Presently,some key scientific issues of S-PSCs remains unsolved,especially how to construct a superposition interface with excellent electrical properties.In this paper,we investigated the interfacial contact systematically,and the photoelectric properties of S-PSCs are further improved through interface modification.(1)Based on four common organic hole transport materials,poly-triarylamine(PTAA),poly-3-hexylthiophene(P3HT),2,2',7,7'-tetrakis-(N,N-di-pmethoxyphenylamine)-9,9'-spiro bifluorene(Spiro-OMeTAD)and poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)(PEDOT:PSS),we explored the key factors on the stackable interfaces in S-PSCs.Studies reveal that the electrical contact of the stackable interface in S-PSCs is closely related to the material electrical conductivity and mechanical elasticity.The continuous applying/releasing pressure tests shows that PEDOT:PSS has good elasticity.When the two electrodes are in contact,sufficient elastic deformation enables the effective physical contact to be formed between two electrodes,in turn endowing the stackable interface with good electrical contact.The S-PSCs based on PEDOT:PSS obtained a PCE of 10.8%,which is obviously superior to that achieved by other hole transport materials.This study provides an experimental basis for the configuration construction and performance improvement of S-PSCs.(2)On the basis of the above research,we added 1,6-hexanediamine iodine(HDADI)to regulate the properties of PEDOT:PSS.The HDADI can effectively reduce the work function of PEDOT:PSS(4.8 eV),close to the work function of the FTO(4.7 eV),and beneficial to reduce the interface barrier between PEDOT:PSS and FTO,in turn facilitating the transfer of photogenerated charges.Secondly,the viscosity of PEDOT:PSS increases with the addition of HDADI.It can further reduce the interface resistance and improve the photoelectric performance of the S-PSCs.Due to the large viscosity of the modified PEDOT:PSS,the structure of the original S-PSCs can be further simplified.In the simple configuration,PEDOT:PSS can be directly stacked with other functional layers.Electrochemical impedance spectroscopy(EIS)shows that this simplified structure still mantains good interfacial electric contact.By optimizing the thickness of the PEDOT:PSS layer,the simplified S-PSCs achieved a PCE of 12.3%.