利用原位红外光谱研究钙钛矿复合半导体CH_3NH_3PbI_3的稳定性

利用高压原位红外光谱法实时跟踪监测了CH_3NH_3PbI_3在高压氮气以及不同含量氧气气氛中加热时的变化规律.发现CH_3NH_3PbI_3对氧气十分敏感,当氮气中含有1%(体积分数)的氧气时,CH_3NH_3PbI_3加热到150℃发生分解;继续提高氧气含量到21%,温度升高到100℃时CH_3NH_3PbI_3即发生分解;若在常压高纯氮气中加热,其分解温度则能提高到250℃;若将氮气压力提高到4.0 MPa,CH_3NH_3PbI_3的分解温度进一步提高到270℃.实验结果表明,提高压力和减少环境中的氧含量是改善钙钛矿复合半导体稳定性的有效方法.相应地,复合半导体光电子器件的热处理过程可以在更高的温度下进行,从而有希望获得性能更加优良的钙钛矿复合半导体光电子器件.

Investigation on Stability of Perovskite Semiconductor CH3 NH3 PbI3 by In-situ FTIR Spectroscopy

Perovskite hybrid semiconductors CH3NH3PbX3(X=Cl, Br, I) have attracted much interests of the chemists and material scientists due to their advantages including facile preparation, low cost and excellent optoelectronic properties. However, the poor stability of these hybrid semiconductors severely frustrated their practical applications, thus it is very important to investigate their decomposition process and explore the new route to improve their stability. Here we investigated the thermal decomposition process of CH3 NH3 PbI3 using an in-situ Fourier transformation infrared( FTIR) spectrometer. It was found that the stability of CH3 NH3 PbI3 was rather sensitive to the existence of oxygen, it began to decompose at 150 ℃ when 1%( volume fraction) oxygen was introduced into the nitrogen atmosphere. In comparison, its decomposition temperature strikingly increased to 250 ℃ when it was heated in pure nitrogen of atmospheric pressure. It was rather surprising that the decomposition temperature of CH3 NH3 PbI3 further increased to 270 ℃ when the pressure of nitrogen in-creased to 4. 0 MPa. This phenomenon reveals that the thermal stability of CH3 NH3 PbX3 should be greatly im-proved by applying an even high pressure, thus the post-treatment of photovoltaic devices could be performed at much higher temperature and even better performance can be anticipated.