Nadinov Issatay, Almasabi Khulud, Gutiérrez-Arzaluz Luis, Thomas Simil, Hasanov Bashir E, Bakr Osman M, Alshareef Husam N, Mohammed Omar F
Advanced Membranes and Porous Materials Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
Materials Science and Engineering, Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia.
ACS Cent Sci. 2023 Nov 3;10(1):43-53. doi: 10.1021/acscentsci.3c00562. eCollection 2024 Jan 24.
One of the most effective approaches to optimizing the performance of perovskite solar cells is to fully understand the ultrafast carrier dynamics at the interfaces between absorber and transporting layers at both the molecular and atomic levels. Here, the injection dynamics of hot and relaxed charge carriers at the interface between the hybrid perovskite, formamidinium lead bromide (FAPbBr), and the organic electron acceptor, IEICO-4F, are investigated and deciphered by using femtosecond (fs) mid-infrared (IR), transient absorption (TA), and fluorescence spectroscopies. The visible femtosecond-TA measurements reveal the generation of hot carriers and their transition to free carriers in the pure FAPbBr film. Meanwhile, the efficient extraction of hot carriers in the mixed FAPbBr/IEICO-4F film is clearly evidenced by the complete disappearance of their spectral signature. More specifically, the time-resolved results reveal that hot carriers are injected from FAPbBr to IEICO-4F within 150 fs, while the transfer time for the relaxed carriers is about 205 fs. The time-resolved mid-IR experiments also demonstrate the ultrafast formation of two peaks at 2115 and 2233 cm, which can be attributed to the C≡N symmetrical and asymmetrical vibrational modes of anionic IEICO-4F, thus providing crystal clear evidence for the electron transfer process between the donor and acceptor units. Moreover, photoluminescence (PL) lifetime measurements reveal an approximately 10-fold decrease in the donor lifetime in the presence of IEICO-4F, thereby confirming the efficient electron injection from the perovskite to the acceptor unit. In addition, the efficient electron injection at the FAPbBr/IEICO-4F interface and its impact on the C≡N bond character are experimentally evidenced and align with density functional theory (DFT) calculations. This work offers new insights into the electron injection process at the FAPbBr/IEICO-4F interface, which is crucial for developing efficient optoelectronic devices.
优化钙钛矿太阳能电池性能最有效的方法之一是在分子和原子水平上全面了解吸收层与传输层界面处的超快载流子动力学。在此，通过使用飞秒（fs）中红外（IR）、瞬态吸收（TA）和荧光光谱，研究并解析了混合钙钛矿甲脒溴化铅（FAPbBr）与有机电子受体IEICO - 4F之间界面处热载流子和弛豫电荷载流子的注入动力学。可见飞秒TA测量揭示了纯FAPbBr薄膜中热载流子的产生及其向自由载流子的转变。同时，混合FAPbBr/IEICO - 4F薄膜中热载流子的有效提取通过其光谱特征的完全消失得到了明确证明。更具体地说，时间分辨结果表明，热载流子在150 fs内从FAPbBr注入到IEICO - 4F，而弛豫载流子的转移时间约为205 fs。时间分辨中红外实验还证明了在2115和2233 cm处两个峰的超快形成，这可归因于阴离子IEICO - 4F的C≡N对称和不对称振动模式，从而为供体和受体单元之间的电子转移过程提供了清晰的证据。此外，光致发光（PL）寿命测量表明，在存在IEICO - 4F的情况下，供体寿命大约降低了10倍，从而证实了从钙钛矿到受体单元的有效电子注入。此外，FAPbBr/IEICO - 4F界面处的有效电子注入及其对C≡N键特征的影响通过实验得到了证明，并与密度泛函理论（DFT）计算结果一致。这项工作为FAPbBr/IEICO - 4F界面处的电子注入过程提供了新的见解，这对于开发高效光电器件至关重要。
