Interface Regulation Of Inverted Perovskite Solar Cell Based On Nickel Oxide

With the optimized synthesis approach of halide perovskite（PVSK）and the improvement of device structure,power conversion efficiency（PCE）of perovskite solar cells（Perovskite Solar Cells,PSCs）has been greatly increased in recent years.Inverted PSCs with p-i-n structures,can be applied in tandem solar cell devices,and have been widely studied for their low-temperature fabrication and small hysteresis properties.At present,nickel oxide（NiO_x）is widely used as hole transport layer（HTL）in p-i-n devices.Although NiO_x is low cost and shows excellent chemical stability,multiple types of defects at the interface between NiO_x and PVSK severely impact the PCE and stability of the inverted solar cell devices.Although some studies have improved the deposition processes or applied interface modifiers to reduce certain type of defects at the NiO_x/PVSK interface,it is difficult to realize a synergistic passivation of multiple types of defects at the interface,and the improvement of device performance is limited.Therefore,a facile interfacial modification method is proposed in this thesis to realize synergistic passivation of different types of defects.By applying a type of organic salt—pyridine p-toluene sulfonate（PPTS）at the NiO_x/PVSK interface,we achieved dramatic improvements of PCE on both narrow-bandgap and wide-bandgap PSCs.Specifically,research contents of this work are as follows:First,this thesis studies the passivation mechanism of various types of defects at the NiO_x/PVSK interface.By analyzing the changes of molecular structure characteristics and surface chemical contents upon PPTS interaction with NiO_x and PVSK,the anchorage of functional groups on multi-type defects of PPTS is elucidated.By studying the charge carrier dynamics of perovskite thin films,it is shown that PPTS can effectively inhibit non-radiative recombination.In particular,this thesis analyzes the interaction between anionic/cationic moieties of PPTS and positively/negatively charged defects with density functional theory,as well as the elimination and bridging effects of PPTS on multiple defect states.Finally,the synchronous passivation mechanism of PPTS for HTL/PVSK interfacial defects was clarified.Then,by applying the synchronous passivation effects of PPTS on multiple defects at device interfaces,we effectively improved the PCEs of PSCs with both narrow-bandgap and wide-bandgap PVSKs,and the effects of synchronous passivation on device performance were explored.Through a series of device characterizations,we found that the introduction of PPTS can significantly reduce the interfacial defect density of solar cell devices,thus optimizing the ideal factor and increasing the parallel resistance therein.Based on these positive effects,voltage of the devices is notably increased（narrow-bandgap PSCs:1.02 V to 1.08 V;wide-bandgap PSCs:1.08 V to 1.10 V）,with device PCEs correspondingly improved（narrow-bandgap PSCs:18%to 20%;wide-bandgap PSCs:17%to 18%）.In the meantime,the reduction of interfacial defect states also enhances the stability of devices.This thesis achieves synergistic passivation of multiple defects at HTL/PVSK interface via the interaction between the anions/cations of organic salt PPTS and interfacial defects with different charge states,with voltage and PCEs of inverted PSCs with different PVSK compositions consequently improved.This work provides a simple and effective strategy to solve the interfacial problem of inverted NiO_x-based PSCs.