The 64th JSAP Spring Meeting, 2017

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13 Semiconductors » 13.10 Compound solar cells

[14p-B6-1~15] 13.10 Compound solar cells

Tue. Mar 14, 2017 1:15 PM - 5:15 PM B6 (B6)

Tomah Sogabe(UEC), Kentaroh Watanabe(Univ. of Tokyo)

1:15 PM - 1:30 PM

▲ [14p-B6-1] Bandgap Engineering of Sol-Gel Synthesized Zn1−xMgxO films as Electron-Transporting
Layers for PbS Colloidal Quantum Dot Solar Cells

〇(D)CHAO DING1,6, Yaohong Zhang1, Shuzi Hayase2,5, Yuhei Ogomi2, Taro Toyoda1,5, Kenji Yoshino3,5, Takashi Minemoto4,5 (1.Univ. Electro-Commun., 2.Kyushu Inst. Tech., 3.Univ. Miyazaki, 4.Ritsumeikan Univ., 5.CREST JST, 6.CSC)

Keywords:Bandgap Engineering, Quantum Dot Solar Cell, Electron-Transporting Layers

Colloidal quantum dots solar cells (CQDSCs) have recently reached promising power conversion efficiencies (η) of over 11%. We found that the tail of states in the conduction band of the normal metal oxide layer (ZnO or TiO2) can limit the achievable CQDSC efficiency. In order to achieve high performance CQDSCs, there is a great need and growing interests to develop novel electron-transporting layer (ETL) materials with tunable bandgaps and energy levels, high transparency, and excellent carrier transporting properties. By continuously tuning the zinc oxide conduction band position via magnesium doping, we probe this critical loss pathway in ZnO–PbS CQDSCs and optimize the energetic position of the tail of states. This resulted in large enhancements in Voc (from 475 mV to 492mV) and Jsc (from 24mA/cm2 to 26 mA/cm2) as well as the energy conversion efficiency (from 6.08% to 7.10%). From the PL spectra of Zn1-xMgxO films, the sample with x=0.1 shows the lowest defect emission, suggested the defect concentration can decrease when Mg with appropriate concentration is doped.Voc and Jsc are enhanced largely when Zn1−xMgxO (x=0.1) was used as the ETL. A maximum efficiency of 7.10% (0.16 cm2) has been achieved, which is 16.7% higher compared to that of the devices without Mg doping (η=6.08%). The improvement in the photovoltaic properties is considered to result from the defect passivation (improved Jsc) and the Fermi level in the ZnMgO layer had move up (improved Voc) by appropriate Mg doping in the ZnO electron-transporting layer.