Organolead Halide Perovskite Solar Cells with Reduced Hysteresis Fabricated by Laser Deposition Method
Masayuki Chikamatsu a, Koji Matsubara a, Hitoshi Tampo a, Takeshi Sugita a, Tetsuhiko Miyadera a
a National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference Asia-Pacific Hybrid and Organic Photovoltaics (AP-HOPV17)
Yokohama-shi, Japan, 2017 February 2nd - 4th
Organizers: Tsutomu Miyasaka and Iván Mora-Seró
Oral, Tetsuhiko Miyadera, presentation 140
Publication date: 7th November 2016

 Organolead halide perovskite solar cells (PVS) have attracted much attention because of their high power conversion efficiencies (PCE). In spite of the rapid development of this field, there still have been some difficulties in fabricating the high performance device with sufficient reproducibility. Moreover, the current hysteresis can be an important issue for the precise evaluation of the device characteristics and fundamental analysis of working mechanism. The construction of the well-controlled fabrication method and fundamental analysis of the device characteristics are required for the further development of this field.

 We have been focusing on the development of vacuum deposition method for the precise fabrication control of the PVS. Instead of using thermal heater we used continuous-wave IR laser to evaporate the materials.[1] Deposition control of amine halide had been difficult because of the gas generation during the deposition. The use of the laser deposition system reduced the gas generation and succeeded in the precise control of the deposition of PVS. Solar cells were fabricated based on the OPV-type architecture (ITO/NiOx/PCDTBT/CH3NH3PbI3/PCBM/BCP/Al). The best PCE in this study was 15.7% for forward scan and 16.0% for backward scan. The hysteresis was particularly reduced.The use of the OPV-type architecture has been reported to be beneficial for the elimination of hysteresis. In addition to the use of OPV-type architecture, highly controlled perovskite films or interfaces may be important for the reduction of hysteresis.

 In order to investigate the origin of current hysteresis, which is currently under discussion, transient current during current-voltage measurement was analyzed. The transient current with the step voltage application can be well fitted with simple exponential function.

I(t) = I0 exp{-(t/τ)} + I1

When the results of the forward scan and backward scan for the same bias voltage were compared, the values of saturation current (I1) were not the same value. Moreover, the time constant (τ) depends on the voltage sweep rate. One of the origins of hysteresis is reported to be capacitance component that may exists at the interface, however, our results suggests that it cannot be explained only by capacitance component. The effect of ferroelectricity or ion migration should be also taken into account. The detail analysis of the current transient would be helpful for the further investigation of hysteresis issue. 

[1] T. Miyadera et al., ACS Appl. Mater. Interfaces 2016, 8, 26013−26018. 

 This work is financially supported by the new energy and industrial technology development organization (NEDO).

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