Photocurrent detected 2D spectroscopy via pulse shaper: insights and strategies for optimally untangling the nonlinear response

Abstract: Action-detected two-dimensional electronic spectroscopy (A-2DES) provides valuable insights into ultrafast dynamics within functional materials and devices by measuring incoherent signals like photocurrent. This work details the implementation and optimization of a pulse-shaper-based A-2DES setup, focusing on methodological strategies crucial for acquiring high-fidelity data. We present a comprehensive analysis of phase modulation routines, elucidating the critical interplay between pattern parameters (N, $\mathrm{n}\mathrm{i}$), pattern repetitions ($\mathrm{N}\mathrm{rep}$), laser repetition rate, and acousto-optic pulse shaper constraints (e.g., streaming rate, RF generator nonlinearities). Utilizing a perovskite solar cell as a model system, we systematically identify and characterize significant inaccuracies inherent to A-2DES measurements. These include distortions originating from Fourier transform processing of improperly trimmed time-domain data (phase leakage), signal accumulation effects due to insufficient sample response discharge between pulse sequences at high repetition rates, and shortcomings induced by pulse shaper operation at elevated streaming powers. Crucially, we demonstrate robust data post-processing strategies, including precise data point selection for Fourier analysis and phase correction routine, to effectively mitigate these imperfections and retrieve accurate 2D spectra. This rigorous methodological investigation and anomalous features characterization provides essential guidelines for optimizing pulse-shaper-based A-2DES experiments, ensuring data integrity and enabling reliable extraction of complex photophysical information in complex systems.