High-EfficiencySolar Cells Based On PbX Quantum Dots

Strongly quantum-confined PbX(X?S,Se,Te)quantum dots(QDs)possess high absorption coefficient and broad spectral tunability matching with the Sun's wide spectrum.These unique features as well as the facile solution processing and favorable device stability make PbX QDs ideal photovoltaic materials for low-cost solar cells.With similar power conversion efficiency(PCE)compared to organic solar cells and dye-sensitized solar cells(NREL),PbX QDs solar cell has become one of most promising new-generation solar cells.To fully realize the potential of nanocrystal materials,more efforts should be devoted to the research on nanocrystal solar cells,which is valuable for the furture industrialization of new photovoltaic devices.However,despite the recent rapid progress,PbX QDs solar cells still show unsatisfactory efficiency(far lower than the theoretical value)and thus way off industrialization.Therefore,more research needs to be done to further promote the development of materials and device based on PbX QDs.In this thesis,the QDs sythesis.film deposition and device structure were comprehensively optimized.Specificly as follows:Chapter 1:The introduction of PbX QDs solar cells.The properties of QDs and fundamentals of solar cells were briefly introduced.And the progress of PbX QDs device was outlined.Chapter 2:The solvent effect on device performance and fabrication processing in PbS QDs inverted solar cells.Due to the inoffensive feature of aprotic ACN,less trap states are introduced during the rinsing process compared to the normally used MeOH.it was firstly discovered that ACN had a "cracks-repairing,effect when employed as the rinsing solvent for PbS QDs solar cells during the solid-state ligand exchange process.Furthermore,a certified PCE of 11.2%(lab champion PCE of 11.8%)was achieved with only 3 deposition steps for the photoactive layers(normally 10 steps),which is the highest certified/reported efficiency to date for PbX QDs photovoltaic devices using the solid-state ligand exchange method.Our results present a promising method to reduce device fabrication complexity.Chapter 3:The device optimization and interface modification for PbS conventional solar cells.The efficient quantum junction structure was firstly adopted in PbS QDs conventional devices.With the introduction of a unique conjugated polymer as the hole transport material,the exciton dissociation and hole extraction at the anode were improved,which lead to a record-high PCE of 8.45%for the conventionally structured PbS QDs solar cells.Chapter 4:The synthesis of PbX QDs doped by halogen and their application in photovoltaic device.We introduced highly reactive halogen precursors in the synthesis of PbX QDs and explore their effects on the morphology,optical properties and doping of QDs.The controllable n-type doping for PbX was realized and the P-N junction based on these gradient-doped QDs was applied in PbS conventional solar cells with QDs exchanged by 1,3-benzenedithiol(BDT),resulting in better device performance.In summary,this thesis systematically describes the effect of QDs synthesis,film deposition,and device structure on the performance of PbX QDs solar cells which will promote the fundamental research of QDS solar cells and their practical application in the future.