Jašinskas Vidmantas, Franckevičius Marius, Gelžinis Andrius, Chmeliov Jevgenij, Gulbinas Vidmantas
Department of Molecular Compound Physics, Center for Physical Sciences and Technology, Saulėtekio av. 3, VilniusLT-10257, Lithuania.
Institute of Chemical Physics, Faculty of Physics, Vilnius University, Saulėtekio av. 9, VilniusLT-10222, Lithuania.
ACS Appl Electron Mater. 2023 Jan 11;5(1):317-326. doi: 10.1021/acsaelm.2c01346. eCollection 2023 Jan 24.
The best perovskite solar cells currently demonstrate more than 25% efficiencies, yet many fundamental processes that determine the operation of these devices are still not fully understood. In particular, even though the device performance strongly depends on charge carrier transport across the perovskite layer to selective electrodes, information about this process is still very controversial. Here, we investigate charge carrier motion and extraction from an archetypical CHNHPbI (MAPI) perovskite solar cell. We use the ultrafast electric-field-modulated transient absorption technique, which allows us to evaluate the electric field dynamics from the time-resolved electroabsorption spectra and to visualize the motion of charge carriers with subpicosecond time resolution. We demonstrate that photogenerated holes drift across the mesoporous TiO/perovskite layer during hundreds of picoseconds. On the other hand, their extraction into the spiro-OMeTAD hole transporting layer lasts for more than 1 nanosecond, suggesting that the hole extraction is limited by the perovskite/spiro-OMeTAD interface rather than by the hole transport through the perovskite layer. Additionally, we use the ultrafast time-resolved fluorescence technique that reveals fluorescence decay during tens of picoseconds, which we attribute to the spatial separation of electrons and holes.
目前，性能最佳的钙钛矿太阳能电池的效率已超过25%，然而，许多决定这些器件运行的基本过程仍未被完全理解。特别是，尽管器件性能很大程度上取决于电荷载流子穿过钙钛矿层传输到选择性电极的过程，但关于这一过程的信息仍然存在很大争议。在此，我们研究了典型的CHNHPbI（MAPI）钙钛矿太阳能电池中的电荷载流子运动和提取过程。我们使用了超快电场调制瞬态吸收技术，该技术使我们能够从时间分辨电吸收光谱中评估电场动力学，并以亚皮秒时间分辨率可视化电荷载流子的运动。我们证明，光生空穴在数百皮秒内穿过介孔TiO/钙钛矿层漂移。另一方面，它们进入螺环-OMeTAD空穴传输层的提取过程持续超过1纳秒，这表明空穴提取受钙钛矿/螺环-OMeTAD界面限制，而非空穴穿过钙钛矿层的传输。此外，我们使用了超快时间分辨荧光技术，该技术揭示了数十皮秒内的荧光衰减，我们将其归因于电子和空穴的空间分离。
