Role of Central Metal Ions in 8‐Hydroxyquinoline‐Doped ZnO Interfacial Layers for Improving the Performance of Polymer Solar Cells

Abstract

Optimizing the function of interfacial materials between the photoactive layer and the metal cathode is critical for realizing high‐efficiency organic solar cells (OSCs). The charge‐collecting layer requires a material with an excellent electrical property to improve the charge collection efficiency and decrease the leakage current that increases the power conversion efficiency (PCE). In this study, the performance of sol–gel‐derived modified cathode interfacial (ZnO) layers, prepared by an appropriate doping of metal (M = Al, Ga, and Mn)quinoline (Q) groups in OSCs, is demonstrated and evaluated. The light absorption of the photoactive layer is improved upon incorporating an interfacial layer into the OSCs. The PCE of the GaQ:ZnO‐based device is higher than that of the AlQ:ZnO and MnQ:ZnO‐based devices, attributed to an improved exciton dissociation rate, enhanced carrier transport, greater electron mobility, and a lower work function. Incorporating a GaQ:ZnO interfacial layer into a thieno[3,4‐b]thiophene/benzodithiophene:[6,6]‐phenyl‐C71‐butyric acid methyl ester (PTB7:PC71BM) OSC increases the PCE from 7.51% to 8.44%, and incorporating it into a poly[[2,6′‐4‐8‐di(5‐ethylhexylthienyl)benzo[1,2‐b:3,3‐b]dithiophene][3‐fluoro‐2[(2‐ethylhexyl) carbonyl]thieno[3,4‐b]thiophenediyl:[6,6]‐phenyl‐C71‐butyric acid methyl ester (PTB7‐Th:PC71BM) (PTB7‐Th:PC71BM) OSC increases the PCE from 8.11% to 9.02%.

Effect of ZnO Electron Extraction Layer on Charge Recombination and Collection Properties in Organic Solar Cells

“…It is also easy to synthesize and can be processed by a cost-effective solution fabrication process. 30,31 There have been reports illustrating the great impact of ZnO morphology and surface properties on the cell performance. 32,33 The performance of OSCs is also dependent on the deposition of the ZnO EEL, including ZnO solution formulation, 34 process condition, 35 and postdeposition treatment.…”

“…Among different EEL choices, ZnO is one of the most attractive materials because of its high optical transparency, high electron mobility, and environmentally friendly attributes. It is also easy to synthesize and can be processed by a cost-effective solution fabrication process. , There have been reports illustrating the great impact of ZnO morphology and surface properties on the cell performance. , The performance of OSCs is also dependent on the deposition of the ZnO EEL, including ZnO solution formulation, process condition, and postdeposition treatment . However, much research effort is desired to improve the understanding of charge recombination and collection properties for efficient and stable operation of OSCs.…”

Organic–inorganic hybrid cathode interlayer materials for efficient organic solar cells

“…66 Hao and co-workers employed different metal ions chelated by 8-hydroxyquinoline into ZnO (Table 1). 67…”

Materials for Interfaces in Organic Solar Cells and Photodetectors

“…A thin ZnO interlayer can assist the reduction of Rs but also resulting in reducing its ability to protect the active layer. To solve this problem, applying doped ZnO instead of the pristine one is a commonly used method, ,, such as Al-doped ZnO. Because of its high conductivity, even the thicker doped AZO layer still achieves a low Rs and a good protection.…”