High efficiency and stable solid-state perovskite solar cell (PSC) was discovered for the first time in 2012 by our group. The first version of PSC was composed of the light absorbing material of methylammonium lead iodide, MAPbI3 (MA = CH3NH3), and the hole conducting spiro-MeOTAD, which delivered a power conversion efficiency of 9.7% and showed long-term stability for 500 h without encapsulation. This work was reported in Scientific Reports, 21 August, 2012. Since our first report on the stable and high efficiency solid-state PSC, research activities on perovskite photovoltaics have been increased exponentially. As a result, the record efficiency of PSC reached 25.5% in 2020, achieved by UNIST team, which now surpassed the conventional high efficiency thin film technologies based on CIGS and CdTe.
In Park’s group, we have been working on super high efficiency PSC toward theoretical efficiency of over 30%, long-term stability under light soaking and 85 oC/85% damp heat condition, large-area coating and module fabrication, and new material design for commercialization and next generation photovoltaics.
Memristors named as compound words of memory and resistor refer to memory devices which save data by resistive switching. Structure of memristor devices is composed of top metal electrode, switching medium and bottom electrode. Due to this simple device structure. Lower cell size and high writing speed than those of other next generation memory devices can be realized theoretically.
Various materials such as oxide, organic and chalcogenide have been applied to memristor. However, they have been suffered from high operating voltage over 1V and low on/off ratio less than 10^3, which drops efficiency of memristor devices. To solve these problems, halide perovskite materials have been applied to memristor devices from 2016 because halide perovskite materials exhibit operating voltage less than 0.5 V and higher on/off ratio than 10^5 because of low activation energy for ion migration and ultra-low dark current.
Purpose of our group’s memristor research is to develop memristor devices with high performance based on halide perovskite materials. Up to now, our group has developed memristor devices which show operating voltage less than 0.3 V and on/off ratio higher than 10^7 by using 0,1,2 and 3-dimensional halide perovskite materials.
The emergence of inorganic organic hybrid perovskites which have superior properties formed with solution-processable crystalline semiconductors, provides new opportunities for large-area, low-cost and high purity light-emitting diodes (LEDs) ideal for display and solid-state lighting applications.
In our lab, perovskite materials with various composition and structure such as perovskite nano crystal have been studied for the perovskite LED. Toward high efficient Red, Green, Blue and IR region LED, we will do researh based on our fabricating skill for high quality perovskite film.