Interface Optimization For Highly Efficient PbS Quantum Dot Solar Cells

Colloidal quantum dot(CQD)solar cells based on lead sulfide(PbS)have attracted tremendous scientific and industrial interest due to their low-temperature solution processing,extremely strong quantum confinement effect,superior air stability after iodide passivation and strong multiple exciton generation(MEG)effect.During the past decade,the power conversion efficiency(PCE)of PbS CQD solar cells has reached to 12%,partly due to the efforts in charge transport layer optimization.Nevertheless,the highly efficient charge transfer materials in CQD photovoltaic devices are extremely limited to date and usually show numerous surface defects.To solve the aforementioned drawbacks,it is urgent to reduce the defects of the existing materials and develop more efficient charge transport materials.Here,in order to improve the device performance,we introduced passivating agents in ZnO nanoparticles,and meanwhile developed new charge transport materials,specifically as follows:Chapter 1:Synthesis of cesium-doped ZnO(Cs-doped ZnO)nanoparticle as electron transport layer for efficient PbS CQD solar cells.In this chapter,we first reported the synthesis of cesium(Cs)doped-ZnO nanoparticles for application in PbS CQD solar cells by a facile wet chemistry synthetic protocol.A combination of characterizations indicated that 5%molar ratio Cs doped ZnO exhibit the optimal optical and electrical properties.Consequently,the PbS CQD solar cells adopting 5%Cs-doped ZnO as electron transport layer achieved the best PCE of 10.43%,while device using pristine ZnO nanoparticle only exhibit a PCE of 9.20%,which can be attributed to the reduced interfacial recombination and improved charge extraction at the PbS/ZnO interface.Chapter 2:Tin oxide(SnO2)as electron transport layer(ETL)for efficient PbS CQD solar cells.In this work,we first tried to apply commercial SnO2 nanoparticles in PbS CQD solar cells.Experiments indicate that it is hard to improve performance of the CQD devices based on this SnO2 layer.Consequently,we provided a more uniform and dense SnO2 film by using radio frequency(RF)magnetron sputtering for PbS CQD photovoltaic devices.Our SnO2 ETL based devices have achieved a higher efficiency of 8.41%compared to that of the sol-gel ZnO based ones(8.30%).Furthermore,by modifying the SnO2/PbS interface with a thin sol-gel ZnO film,we achieved a best efficiency of 9.47%.Chapter 3:Perovskite nanocrystal(a-CsPbI3)interlayer for efficient PbS quantum dot ink-based solar cells.In this chapter,we modified the PbS-I/polymer interface with a thin a-CsPbI3 nanocrystal film,aiming to improve the energy level alignment between the active layer and hole transport layer.Meanwhile,the introduction of perovskite nanocrystl can promote charge separation and extraction,reduce interfacial charge recombination and then improve the efficiency of the CQD devices.With the optimal conditions,we obtained a best PCE of 10.77%,while a control device only exhibit PCE of 9.50%,which makes CsPbI3 interlayer an effective way to improve the efficiency of PbS CQD solar cells.