Two-dimensional coherent photocurrent excitation spectroscopy of a hybrid lead-halide perovskite solar cell
Carlos Silva, Université de Montréal
Hybrid halide perovskite (for example, CH3NH3PbI3) solar cells now display solar power conversion efficiencies exceeding 20% [1]. In these materials, excitonic and free-carrier regimes of primary photoexcitations are possible depending on crystalline microstructure of the active layer and excitation density [2]. Recent literature suggests that photocarriers in these materials may be large polarons [3], with this notion motivated by observation that charge transport is limited by acoustic phonon scattering, and not by impurities and crystalline defects present ubiquitously in these polycrystalline microstructures. In order to explore the nature of photocarriers in these materials, we implement two-dimensional coherent photocurrent excitation (2D-PCE) spectroscopy as described elsewhere [4] on an optimized solar cell based on CH3NH3PbI3 [5]. Via the time-resolved total correlation spectrum, we identify both excitonic and continuum resonances. By means of temperature dependent measurements of the rephasing zero-time spectrum, we explore the possible polaronic character of the exciton and continuum resonances and address directly whether this measurement reflects such phonon coupling.
References
[1] NREL Solar Cell Efficiency Chart.
[2] Grancini et al, Nat. Photonics 9, 695−701 (2015).
[3] X.-Y. Zhu & V. Podzorov, J.Chem. Phys. Lett. 6, 4758−4761 (2015).
[4] arXiv:1602.04205 [cond-mat.mtrl-sci]
[5] Tao et al, Energy Environ. Sci. 8, 2365 (2015).