Research On The Modified Electrode Layer Of Organic Photovoltaic Devices Based On Zinc Oxide Nanocrystals

Organic solar cells (OSCs) have attracted considerable interest due to the potential forlow cost, lightweight and flexibility. From the view of industrialization, high powerconversion efficiency (PCE), roll-to-roll feasibility and high stability are the necessaryrequirements. Inverted solar cell with ZnO nanocrystals as the electron transport layer cansatisfy the above requirements. But the major concern with ZnO nanocrystals lies in theirproperties, such as high surface-to-volume ratio and low conductivity intrinsic properties,which are the hindrances for their application in organic photovoltaic cells. Herein, weemployed the modified ZnO nanocrystalsas the electron transport layer in the inverted organicsolar cell. The details are the following:Firstly, we used different concentration (0,0.01%,0.05%,0.1%,1%) of modified ZnOnanocrystals as the electron transport layer. It found that both the short-circuit current (JSC)and the fill factor (FF) of the inverted solar cells are considerably improved. Moreever, whenusing0.05%PEO-modified ZnO as the electron transport layer, the power conversionefficiency (PCE) is improved from1.38%to2.06%. The improved performances areattributed to PEO can share the lone electron pair of oxygen with ZnO. The surface traps ofZnO can be effectively passivated, the recombination loss of carriers could be suppressed,reducing the series resistance, improving the electrical coupling of ZnO/active layer. Theseresults are attractive to develope a new strategy to fabricate simple and low-cost electrontransport layers in the large-area roll-to-roll manufacture of organic solar cells.Secondly, we prepared Cesium-doped ZnO(CZO) nanocrystals with differentconcentrations of Cs via sol-gel method. The performances of fabricated inverted devices withthe structure of ITO/CZO/P3HT:PCBM/PEDOT:PSS/Ag are improved by using CZO films aselectron transport layers. Compared with the reference device, CZO-based OSCs’sperformance enhance from3.9to6.91mA/cm2. Cs Doping not only optimizes the bandalignment between the active layers and ETLs but also increases the conductivity. In addition,CZO film is also prepared by using water based sol-gel process. The devices demonstratedsimilar performances with the device prepared using2-methoxyethanol. This method satisfieswith the environmentally friendly and flexible OPV fabraction demand.Finally, we prepared S-doped ZnO(ZnOS-ZnS) nanocrystals with different concentrationof S via an aqueous chemical growth (ACG) process to realize rearrangement at the interfaceof ZnO. In this way, improvement conductivity and level alignment ZnOS films is fabricated.Employing the films as ETL, the PCE enhanced from1.3%to2.47%. This simple preparationconditions and high PCE make the flexible organic photovoltaic production more practical.