Structure Design, Process Optimization And Performance Study Of Organic Tandem Solar Cells

Organic solar cells?OSCs?have been drawing much attention due to their attractive properties such as low cost,good mechanical flexibility,easy manufacturing,light weight and large-area manufacturing compatibility.In recent years,the efficiency of organic solar cells has been improved significantly due to the progress of efficient new materials,device engineering and physics.However,compared with inorganic solar cells,the efficiency of organic solar cells is still to be enhanced.Fabricating tandem solar cells with different-bandgap semiconductors is an effective way to increase the solar cell efficiency.Currently,it is still challenging to fabricate organic tandem solar cells due to the more complicated device structure comparing with the single-junction devices.In this thesis,the following study has been performed to simplify the processing and enhance performance of tandem solar cells:?1?Vacuum-free organic tandem solar cells have been fabricated by using film-transfer laminated PH1000-T as the top electrode.The transfer printed top electrodes instead of vacuum deposited metal electrodes simplies the manufacturing.The fabricated vacuum free tandem solar cells delivered higher efficiency?3.6%?than the two sub-cells?3.2%and 2.6%?.The high fill factor of 0.72 shows the effectiveness of the transfer-printed PH1000-T electrode.?2?The effect of the conductivity of the interconnecting layer has been studied.Conductivity of PEDOT:PSS/PEI interconnecting layer is optimized by changing the compostion of PEDOT:PSS and using different solvents to process the PEI.An optimized conductivity of 0.03 S cm^-1?PEDOT:PSS-m13/PEI?IPA??is obtained that enable us to fabricate tandem solar cells without the need of patterning the interconnecting layer.?3?Adopting PEDOT:PSS-m13/PEI?IPA?as the interconnecting layer,all-plastic multijunction?up to 7 junctions?solar cells have been fabricated.Under one sun illumination,a 7-junction all-plastic solar cell has a Voc of about 5.37 V.The high Voc enables the cells to drive LED and LCD.Due to the all-plastic nature,the devices show excellent flexibility.Up to 5000 bending cycles,almost no performance degradation was observed.?4?PbS QDs have a wide absorption range from the visible to the near-infrared.However,because of the discrete energy level of PbS QDs,there exists an absorption valley in PbS based films that decreases the light harvesting efficiency.Organic-QDs hybrid tandem solar cells with complementary absorption are designed and fabricated.A new interconnecting layer Spiro-MeOTAD/MoO₃/Ag/PEI is designed to fabricate two terminal organic-PbS quantum dot hybrid tandem solar cells.The hybrid device delivered higher efficiency?7.4%?compared with the sub-cells?4.8%and 3.6%?.This provide new insights to combine organic and inorganic materials to more efficiently utilize the solar energy with broad spectrum.