November 5, 2019.
Solar energy is an important energy because it provides a clean energy with infinite amount. Solar cells are devices provide electrical energy converting from solar energy. There are many types of solar cells such as silicon solar cells, thin film solar cells, quantum dot solar cells (QD), organic photovoltaic (OPV) and emerging solar cells etc. At present, the most attractive solar cell is perovskite solar cell that have been drawn interest from researchers and industries worldwide. Perovskite solar cell which includes a perovskite structured compound is derived from the ABX3 crystal structure. Today, efficiency of perovskite solar cell is up to 25.2 %  in 2019 comparing to the amorphous silicon solar cell of about 26 % as seen in Figure 1. The perovskite solar cell is very interesting due to a low weight, low cost, easy fabrication and having a report of energy payback time (EPBT) of about 2-3 months in perovskite solar cell comparing with the amorphous silicon solar cell that EPBT is about 1-2 years .
In this research project, it is focused to improve efficiency of perovskite solar cell as the following.
Fig. 1 Reported timeline of research on solar cell energy conversion efficiencies. 
2. Research on perovskite solar cell
Normally, the structure of perovskite solar cell consists of perovskite layer, electron transporting layer (ETL) and hole transporting layer (HTL) as shown in Figure 2.
Fig. 2 Structure and principle of perovskite solar cell.
In our main research, we focus on investigating the technique for preparing in each layer of perovskite solar cell to improve the efficiency of perovskite solar cell. Figure 3 shows an example of J-V curve of perovskite solar cell that prepared in our laboratory in lab scale and the structure of this solar cell consists of conducting glass FTO/ SnO2/ perovskite layer/Spiro-MeOTA.
Fig. 3 J-V curve and structure of the perovskite solar cell in this research.
We study the effect of temperature by using pre-heat treatment of perovskite layer in two-step deposition method. In this work, the perovskite films are prepared by varying heat treatment conditions. The results of this study were published in the Thin Solid Film journal .
Moreover, during the research project, we have a collaboration with the researchers in National Nanotechnology Center (NANOTEC) and researchers from China. In July 2019, we were visited Shanghai Jiao Tong University, Shanghai, and Suzhou GCL Nano Co., Ltd., Suzhou in order to establish the collaboration for large-scale perovskite solar cell, shown in Figure 4.
Fig. 4 Activity during visiting China in July 2019.
The Suzhou GCL Nano Co., Ltd. have received funding from the investor to improve efficiency of perovskite solar cell in a large-scale area and aimed for a 1 GW perovskite cell production line in place by 2022. Now, the Chinese manufacturer claims that it has already hit 16% conversion efficiency on a large panel and it is confident that 18% could be achieved by the end of the year 2019 .
 Kritsada Hongsith, Sutthipoj Wongrerkdee, Athipong Ngamjarurojana and Supab Choopun, “Efficiency enhancement of perovskite solar cell by using pre-heat treatment in two-step deposition method”, Thin Solid Films 684 (2019) 9–14.
Asst. Prof. Dr. Supab Choopun
Applied Physics Research Laboratory, Dept. of Physics and Materials Science, Fac. of Science, Chiang Mai University, Chiang Mai-50200, Thailand