Alternative Title量子ドット太陽電池とペロブスカイト太陽電池における界面修飾と界面電荷ダイナミクス
Note (General)The present globalization of energy shortage and environmental pollution issues have posed a grave menace to human survival and development. Finding a viable supply of clean, renewable energy is one of the most daunting challenges facing the world. Solar cells as devices that convert solar energy into electricity is the focus of the whole society. However, conventional solar cells have had limited impact in meeting this challenge because of their high pollution, high cost and low power conversion efficiencies. Recently, colloid quantum dot solar cells (CQDSCs) and perovskite solar cells (PSCs) as new generation solar cells have been attracting immense attention owing to their inexpensive solution-based techniques and high theoretical power conversion efficiency. However, stability is still a big problem for CQDSCs and PSCs, and charge dynamics in those solar cells are not clear. To obtain stable CQDSCs and PSCs through interface modification, and reveal the charge dynamics in those solar cells are the central aim of this thesis. This thesis investigated the surface ligand dependent charge carrier dissociation, charge carrier transmission and recombination of CQDSCs, and used novel hole transport materials to modify the interface of CQDSCs and PSCs to reduce the interfacial recombination in CQDSCs and PSCs. In this thesis, I explore a method to obtain air stable PbSe CQDs and surface ligand dependent exciton dissociation, recombination, photovoltaic property, and stability of PbSe solid films and CQDSCs. I select four short ligands, that is, two organic ligands 1,2-ethanedithiol (EDT) and 3-mercaptopropionic acid (MPA); two inorganic ligand cetyltrimethylammonium bromide (CTAB) and tetrabutylammonium iodide (TBAI) to investigate the ligand-dependent air stability, energy level shift, the exciton dissociation, and photovoltaic properties of PbSe CQDSCs. In addition, the charge transfer rate, recombination processes and carrier lifetimes in these CQDSCs were also revealed through ultrafast transient absorption (TA) spectra, and open-circuit transient voltage (Voc) decay measurements. We also explore a method to suppress the interfacial recombination at QDs/Au electrode in CQDSCs by using organic small molecule. We develop a novel donor-π-donor (D-π-D) organic small molecule bis-triphenylamine with spiro(fluorene-9,9’-xanthene) as the conjugated system, named BTPA-4, as a hole selective layer (HSL) in the PbS CQDSCs. We found that the introduction of BTPA-4 as HSL can enhance the open-circuit voltage (Voc), prolong the effective carrier lifetime, reduce the interfacial recombination at PbS QDs/Au interface, and hence improve the device performance. Furthermore, the PbS CQDSCs with BTPA-4 possessed a noticeably stable property for over 100 days of storage under ambient atmosphere that has been the Achilles' heel of other organic HSL for CQDSCs. We also focus on hole transport materials and the interfacial recombination in PSCs. Three triphenylamine-based hole-transport materials (HTMs), named BTPA-4, BTPA-5 and BTPA-6, were used into PSCs. BTPA-6 with four substituted triphenylamine units exhibited a better solar cell performance than BTPA-4 and BTPA-5 which contain two substituted triphenylamine units. BTPA-6 achieved a PCE of 14.4% which nearly matches Spiro-OMeTAD (15.0%). The order of the recombination resistance was found to be in the order of BTPA-4 < BTPA-5 < BTPA-6 < Spiro-OMeTAD, indicating that the electron blocking capability of the HTM is in this order. This trend agrees with the Voc trend of their corresponding solar cells. In addition, BTPA-6 based devices showed better long-term stability than that with Spiro-OMeTAD, which can partially be attributed to the hydrophobicity of BTPA-6 is better than that of Spiro-OMeTAD. The goal of above experiments is to gain a more complete understanding of charge carrier dynamics in CQDSCs and PSCs, so that more efficient materials and architecture for solar cells can be designed in the future.
2017
Collection (particular)国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文
Date Accepted (W3CDTF)2017-12-04T02:02:48+09:00
Data Provider (Database)国立国会図書館 : 国立国会図書館デジタルコレクション