Investigation Of Environmental-friendly Water-soluble Interface Modified Layers For Polymer Solar Cells

Nowadays,Polymer solar cells?PSCs?have been valued and developed under the global energy crisis.Inorganic solar cells have been limited for further development due to the disadvantages of high cost and complex process.Polymer solar cells have been attracted extensive attention and research due to low cost,easy processing,light weight and flexibility.In addition to synthesizing high-performance active layer materials and controlling their morphology,improvement of interface modification materials is also an effective method to enhance PSCs performance.In this research,we selected three types of Environmental-friendly water/alcohol-soluble small molecules as the cathode modification layer,which not only improved the performance of PSCs,but also realized the greenness of processing.The research is mainly carried out from the following aspects:Firstly,the naturally-occurring biological material L-arginine?L-Arg?as cathode-modified electron transport layer?ETL?was applied to an inverted PSCs,which can not only increase the open circuit voltage(V_OC),the short-circuit current(J_SC)and fill factor?FF?,but also improve the energy conversion efficiency?PCE?from 1.90%to 9.00%.The research of ultraviolet electron spectroscopy?UPS?and X-ray photoelectron spectroscopy?XPS?can draw the reason for increasing in the built-in potential of the device,the existence of an interface dipole layer,and addition of L-Arg reducing work function of cathode electrode.At the same time,the reasons for the improvement of device performance were explained in combination with contact angle and impedance tests.In addition,the PCE of the ZnO/L-Arg ETL device was increased to 9.31%and the device stability was significantly improved.The results show that L-Arg with natural biomaterials can be used as the ETL,which provide a new approach for the preparation of low-cost,non-toxic,environmental-friendly ETL for PSCs.Secondly,two kinds of water-soluble Phen derivatives were used as cathode-modified electron transport layers based on traditional PSCs based on PTB7-Th:PC₇₁BM.The results showed that the PCE of Phen-1 and Phen-2 as ETL reach 8.55%and 9.38%,respectively.The main reasons for the improvement performance of PSCs were obtained through analysis of atomic force microscope,contact angle,dark conduction,exciton dissociation and impedance.Because Phen derivatives with sulfonate and conjugated structures have an optimized effect on the surface morphology of the active layer,thereby reducing the contact resistance of the device and improving exciton transmission and collection.Finally,a water/alcohol-soluble hexamethylenetetramine(C₆H₁₂N₄)was used as the cathode-modified ETL to process traditional PSCs based on PTB7-Th:PC₇₁BM.The results showed that C₆H₁₂N₄ ETL was beneficial to improving the performance of the device.Under the conditions of 3.0 mg/mL and 4000 r,the PCE of C₆H₁₂N₄ ETL is up to 7.79%.The main reasons for improving the performance of PSCs were studied by atomic force microscopy,contact angle,dark conduction,exciton dissociation and impedance.The C₆H₁₂N₄ modified active layer exhibits a smoother interface morphology,which is conducive to reducing the obstacle of charge transport and thus reducing the contact resistance of the device.