Zhao Xi, Long Run
College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People's Republic of China.
J Phys Chem Lett. 2020 Dec 17;11(24):10298-10305. doi: 10.1021/acs.jpclett.0c03289. Epub 2020 Nov 23.
One may expect that isotopic exchange has no influence on charge carrier lifetime and perovskite solar cell performance because isotopic effects do not affect the fundamental electronic structure of materials. Experiments defy this expectation. By performing nonadiabatic (NA) molecular dynamics simulations, we demonstrate that hydrogen and deuterium exchange significantly enhances the excited-state lifetime and stability of CHNHPbI. Replacing lighter hydrogen with heavier deuterium suppresses the collective motions of organic and inorganic components, thus enhancing lattice stiffness and decreasing the NA coupling. Isotopic exchange further reduces NA coupling by localizing electron wave functions for separation of electrons and holes, which beats the extended coherence time, slowing down nonradiative electron-hole recombination from CHNDPbI to CDNDPbI with respect to the pristine system. The unchanged fundamental electronic structure together with the prolonged carrier lifetime and enhanced stability rationalize the improvement of the deuterated CHNHPbI solar cells. Our work provides valuable insights into isotope effects for the design of high-performance perovskite photovoltaic and optoelectronic devices.
人们可能认为同位素交换对电荷载流子寿命和钙钛矿太阳能电池性能没有影响，因为同位素效应不会影响材料的基本电子结构。然而实验却与这一预期相悖。通过进行非绝热（NA）分子动力学模拟，我们证明氢氘交换显著提高了CHNHPbI的激发态寿命和稳定性。用较重的氘取代较轻的氢抑制了有机和无机组分的集体运动，从而提高了晶格刚度并降低了非绝热耦合。同位素交换通过使电子波函数局域化以实现电子与空穴的分离，进一步降低了非绝热耦合，这延长了相干时间，相对于原始体系减缓了从CHNDPbI到CDNDPbI的非辐射电子-空穴复合。基本电子结构不变，同时载流子寿命延长且稳定性增强，这解释了氘化CHNHPbI太阳能电池性能的提升。我们的工作为高性能钙钛矿光伏和光电器件设计中的同位素效应提供了有价值的见解。
