Study On Organic Solar Cells Based On Interface Modification And Analysis Of Equivalent Circuits

Clean energy is a necessary condition for reducing atmospheric pollution and greenhouse gas emissions and ensuring sustainable development of society,so it is necessary to develop renewable energy.Solar energy is considered to have the highest potential in renewable energy and other alternative energy resources.It is inexhaustible and environmentally friendly,especially organic solar cells?OSCs?,which have been widely concerned by the industry.In recent years,the efficiency of organic solar cells based on bulk heterojunction?BHJ?structures has been constantly updated.Although the current energy conversion efficiency of organic solar cells has exceeded 17%,it is far from the actual application standard.To further improve the efficiency and stability,the interface engineering between the electrode and the photoactive layer is a key problem.In organic solar cells,the interface modification mainly includes the hole transport layer interface modification and the electron transport layer interface modification,so the improvement of the performance of these two transport layers plays a very important role in the performance of the organic solar cell.In this paper,the interface modification of the electron transport layer is mainly carried out as follows:1.We have prepared a reverse organic solar cell with a device structure of FTO/ZnO/CaF₂/P3HT:PC₆₁BM/MoO₃/Ag,and use calcium fluoride?CaF₂?to modify the surface of ZnO thin film as an electron transporting layer for an inverted organic solar cell.The results show that the CaF₂ layer can passivate the surface traps of the ZnO thin film,reduce the energy band barrier between the PC₆₁BM layer and the ZnO layer,enhance the ohmic contact with the photoactive layer,improve the charge transport efficiency,inhibit the recombination of electrons and holes at the interface,and reduce the series resistance of OCSs.The introduction of the CaF₂ layer improves the light absorption of the device,reduces the energy loss of incident light,and facilitates the extraction and collection of charge carriers.As a result,the short-circuit current and the fill factor was greatly improved,and the energy conversion efficiency is significantly increased from 3.21%without CaF₂ layer modification to 4.22%.These results could have special guiding significance for high-efficiency OSCs.2.We have prepared ITO/ZnO/MgF₂/PCDTBT:PC₇₁BM/V₂O₅/Ag as the inverted device structure of organic solar cells,using magnesium fluoride?MgF₂?to modify ZnO film as an electronic transport interface layer,can greatly enhance the performance of the inverted organic solar cell.With a composition of PCDTBT:PC₇₁BM as photoactive layer,the inverted OSC with MgF₂-modified ZnO layer exhibits a good power conversion efficiency?PCE?of 7.01%,which is an amazing enhancement over 5.84%of the device with pure ZnO layer as electron transport layer,which is about 20%higher than that of the device with ZnO layer alone.The improvement in PCE of the OSCs is primarily due to MgF₂-modified ZnO layer enhance electron extraction efficiency and reduces electron-hole recombination,which can be attributed to the formation of an ideal dipole layer at the interface between ZnO layer and photoactive layer,thus adjusting the work function,reducing the energy band barrier and improving the charge transfer efficiency.Furthermore,MgF₂ layer can improve the surface quality and wettability of ZnO layer,thereby improving the interface contact between ZnO layer and photo active layer.These results show that MgF₂-modified ZnO thin film is a simple and effective interface modification approach could have a certain guiding significance for obtaining highly efficient inverted OSCs.