Research Team Led by SNU Professor Lee Chang Hee Explains the Degradation of Perovskite Solar Cells

- Suggestions to Prolong Perovskite Solar Cell Life


▲ SNU Department of Electrical and Computer Engineering Professor Lee Chang Hee (Left), PhD student Lee Hyunho (Right)

 
SNU College of Engineering (Dean Cha Kook-Heon) announces on 23^rd that Professor Lee Chang Hee and PhD student Lee Hyunho from the Department of Electrical and Computer Engineering have discovered the main reason behind the degradation of perovskite solar cells.
 
Perovskite solar cell is a type of solar cell that uses a hybrid organic-inorganic ionic compound of perovskite structure as its light absorbing layer. It is receiving much attention as the next generation solar cell for its high light-to-electrical energy conversion efficiency of 22.7%.
 
However, contrary to the high efficiency, the perovskite solar cell has a short lifetime. It is especially vulnerable to water; hence, its stability is much lower than conventional solar cells. Many researchers have been tackling this issue by manipulating the perovskite components of the light absorbing layer, but have all failed to find a probable solution.
 
In order to resolve this limitation of the degradation of perovskite solar cells, Professor Lee’s team has approached the problem from its roots. They have analyzed the reason for degradation by using an electrode regeneration method that involves removing the electrodes from perovskite cells that have degraded for a fixed amount of time for them to form new electrodes.
 
As a result, the team has discovered that that the iodide ion (I-) of the light absorbing layer decomposes during diffusion to accumulate under the electrode and this chemically reacts with fullerene molecules in the electron transport layer to worsen the electrical properties.
 
When the degraded electrodes are removed, portions of iodide ion between the electrodes and electron transport layer are also removed. The team has demonstrated that the energy conversion efficiency of the perovskite solar cell recovers when new electrodes are formed. Thus, the diffusion of iodide ion in the thin layer of perovskite and its accumulation at the interface of electron transport layer and electrode is the explanation for degradation of perovskite solar cell.
 
Professor Lee explains, “This research has revealed the fundamental reasons behind the degradation of perovskite solar cells. Its implication shall provide guidelines to prolonging the life of the cells.”
 
The research has been featured as the cover article of the April 17^th 2018 issue of the scientific journal “Advanced Energy Materials” that covers energy-related topics. It has been titled “Analysis of Ion-Diffusion-Induced Interface Degradation in Inverted Perovskite Solar Cells via Restoration of the Ag Electrode.”
 
This research has been conducted with the support from the Ministry of Science, ICT, and Future Planning and the Mid-career Researcher Program of the National Research Foundation of Korea.
 
[Reference Links]
1. Research Paper: Hyunho Lee  Changhee Lee, Analysis of Ion‐Diffusion‐Induced Interface Degradation in Inverted Perovskite Solar Cells via Restoration of the Ag Electrode (https://doi.org/10.1002/aenm.201702197)
 
2. Cover Page of the “Advanced Energy Materials”: Perovskite Solar Cells: Analysis of Ion‐Diffusion‐Induced Interface Degradation in Inverted Perovskite Solar Cells via Restoration of the Ag Electrode (Adv. Energy Mater. 11/2018) Hyunho Lee, Changhee Lee, First published: 17 April 2018 (https://doi.org/10.1002/aenm.201870047)
 

▲ Degradation Process of Perovskite Solar Cell as Iodide Ion Escapes from Thin Layer of Perovskite to Accumulate on Interface of Electrode
 

▲ Cover Page of the April 17^th Issue of the “Advanced Energy Materials” Featuring This Research as Its Main Article