Periodic Reporting for period 1 - REPAMPS (Recursive Engineering electronic Properties of Artificial energy Materials with multi-Pulse Spectroscopy)
Okres sprawozdawczy: 2021-05-01 do 2023-04-30
Organic Photovoltaic (OPV) Materials are one of the most popular materials for energy conversion. Besides their many advantages they still present low energy conversion efficiencies. The absence of a complete theoretical description that describes the elementary molecular mechanism governing the charge generation in these systems, including a description of the main factors affecting the photo-induced process prevents further developments in this direction. The main goal of REPAMPS is to provide with a comprehensive description of the photo-induced charge generation in a prototypical OPV material, introducing for the first time several factors commonly disregarded: (1) a first-principles description of the realistic fluctuating material environment; (2) a quantum dynamical description of the ultrafast charge-transfer process which includes the explicit effect of the interacting fields and evaluation of time-resolved optical spectra.
Conclusions of the action: a first-principles model of the P3HT:PCBM electron donor-acceptor system has been developed and published. The achievements of this part of the project reveal the role of the material environment on delocalizing the exciton along the polymer system, before the ultrafast charge-transfer process takes place. Besides, the introduced model can be used to predict linear and nonlinear time-resolved spectra of the P3HT:PCBM blend within the realistic blend fluctuating conditions, directly comparable to available experiments on this system. On other lines, investigations performed on this project on a simple model for this system show that chirped excitation conditions can be used to manipulate the extent of the charge-transfer, representing a promising tool for photocontrolling the charge-transfer process in similar energy materials.
Conclusions of the action: a first-principles model of the P3HT:PCBM electron donor-acceptor system has been developed and published. The achievements of this part of the project reveal the role of the material environment on delocalizing the exciton along the polymer system, before the ultrafast charge-transfer process takes place. Besides, the introduced model can be used to predict linear and nonlinear time-resolved spectra of the P3HT:PCBM blend within the realistic blend fluctuating conditions, directly comparable to available experiments on this system. On other lines, investigations performed on this project on a simple model for this system show that chirped excitation conditions can be used to manipulate the extent of the charge-transfer, representing a promising tool for photocontrolling the charge-transfer process in similar energy materials.
From the beginning of the project, 2 of the 3 work packages (WP) have been fully investigated and addressed.
Year 1 and part of Year 2: the WP1 was fully completed and the milestones and deliverables specified on the project description were addressed completely. The development of the extensive first-principles model of the P3HT:PCBM blend described in the project description took a bit longer than the original time planning due to the high complexity of the model, however, despite this, the delivered investigation and final peer-reviewed publication was successful, and addresses the milestones and goals specified in the WP1 project description. The work related to this WP includes the initial production of source-codes, data manipulation and analysis and results production. All these self-written codes and scripts were used to elaborate the first-principles model using quantum (TDDFT calculations) and classical (Molecular Dynamics) simulations. The intensive model introduces a complete first-principles description of a prototypical realistic P3HT:PCBM photovoltaic blend (1480 PCBM molecules, 845 P3HT molecules) which includes a quantum mechanical description of the photoinduced exciton delocalisation in the electron donor system (P3HT) in the time-dependent (picoseconds timescale) fluctuating environment determined by the P3HT-PCBM blend. This novel model reveals the origin of the homogeneous and inhomogeneous broadening in the simulated linear and two-dimensional spectra of the P3HT:PCBM blend, identifying the role of the environment on the exciton delocalisation after photexcitation, that controls the extent of the charge-transfer process. An extensive configurational analysis of the torsional flexibility along the P3HT chains in the presence of the fluctuating environment and its effect on the exciton delocalisation is performed. The insights from WP1 have been disseminated in 4 international conferences (3 talks and 1 poster) and published in one peer-reviewed publication with open-access (JPCC). Besides, this work was selected to be published as part of The Journal of Physical Chemistry virtual special issue “Early-Career and Emerging Researchers in Physical Chemistry Volume 2”. These developments introduce a quantum-classical description of the exciton delocalisation in a prototypical OPV material (P3HT:PCBM blend) including a extensive description of the role of the environment on the simulated spectra, directly comparable to available experiments.
Year 2: WP2 and part of WP3 were performed. A low-dimensional nonadiabatic model was developed and the explicit effect of the light-driven quantum dynamics for different pulse excitation conditions was investigated. First, a single-pulse dynamics was investigated. An extensive analysis was done of the effect of chirped pulse excitations on the photoinduced electronic wavepacket. The analysis reveals that chirped pulses can be used to manipulated the extent of the charge-transfer in the electron donor-acceptor model, for long times after dissipation (bath/blend). Last, 2-pulse fluorescence time-resolved spectra were simulated and introduced, demonstrating that chirped pulses can be used to enhanced the system dynamical information. This work is presented in a manuscript ready for submission and these insights have been disseminated in 2 talks at international conferences.
Year 1 and part of Year 2: the WP1 was fully completed and the milestones and deliverables specified on the project description were addressed completely. The development of the extensive first-principles model of the P3HT:PCBM blend described in the project description took a bit longer than the original time planning due to the high complexity of the model, however, despite this, the delivered investigation and final peer-reviewed publication was successful, and addresses the milestones and goals specified in the WP1 project description. The work related to this WP includes the initial production of source-codes, data manipulation and analysis and results production. All these self-written codes and scripts were used to elaborate the first-principles model using quantum (TDDFT calculations) and classical (Molecular Dynamics) simulations. The intensive model introduces a complete first-principles description of a prototypical realistic P3HT:PCBM photovoltaic blend (1480 PCBM molecules, 845 P3HT molecules) which includes a quantum mechanical description of the photoinduced exciton delocalisation in the electron donor system (P3HT) in the time-dependent (picoseconds timescale) fluctuating environment determined by the P3HT-PCBM blend. This novel model reveals the origin of the homogeneous and inhomogeneous broadening in the simulated linear and two-dimensional spectra of the P3HT:PCBM blend, identifying the role of the environment on the exciton delocalisation after photexcitation, that controls the extent of the charge-transfer process. An extensive configurational analysis of the torsional flexibility along the P3HT chains in the presence of the fluctuating environment and its effect on the exciton delocalisation is performed. The insights from WP1 have been disseminated in 4 international conferences (3 talks and 1 poster) and published in one peer-reviewed publication with open-access (JPCC). Besides, this work was selected to be published as part of The Journal of Physical Chemistry virtual special issue “Early-Career and Emerging Researchers in Physical Chemistry Volume 2”. These developments introduce a quantum-classical description of the exciton delocalisation in a prototypical OPV material (P3HT:PCBM blend) including a extensive description of the role of the environment on the simulated spectra, directly comparable to available experiments.
Year 2: WP2 and part of WP3 were performed. A low-dimensional nonadiabatic model was developed and the explicit effect of the light-driven quantum dynamics for different pulse excitation conditions was investigated. First, a single-pulse dynamics was investigated. An extensive analysis was done of the effect of chirped pulse excitations on the photoinduced electronic wavepacket. The analysis reveals that chirped pulses can be used to manipulated the extent of the charge-transfer in the electron donor-acceptor model, for long times after dissipation (bath/blend). Last, 2-pulse fluorescence time-resolved spectra were simulated and introduced, demonstrating that chirped pulses can be used to enhanced the system dynamical information. This work is presented in a manuscript ready for submission and these insights have been disseminated in 2 talks at international conferences.
(1) Delivering a first-principles model of a prototypical OPV material that includes a quantum mechanical (TDDFT) description of the photoinduced exciton delocalisation on the electron donor system (P3HT), effect of the fluctuating environment (torsional flexibility in the polymer chains via Molecular Dynamics (MD) simulations and description of the origin of the broadening in the simulated linear and nonlinear spectra for the blend system. (2) Description of the use of chirped pulses to manipulate the extend of the charge-transfer in low-dimensional models describing electron donor-acceptor systems. Introducing a new theoretical scheme based on time-resolved fluorescence signals using a sequence of two pulses delayed in time, and demonstration of the use of chirped pulses (either using a chirped pump and a TL probe or vice versa) to enhance the dynamical system information in the simulate spectra.
Expected results until the end of the project: Investigations performed on WP2 will be extended to include the parametrisation of the blend environment obtained in WP1. Part of this work is already performed and final simulations to achieve this will be done in the upcoming time. These simulations will describe the charge-transfer for a more realistic model. Transient-absorption spectra will be simulated and three-pulse spectroscopies, using the existing EOM-PMA method contained in the project description. The effect of chirped pulses will be investigated, as performed in the previous work (ready for submission), which will demonstrate how tailored pulses can be used to manipulate the charge-transfer process. Last, the SEC strategy remains to be addressed. Due to the ambitious character of the project, the development of the SEC approach has not been able to be performed during the 2021-2023 period of the project, originally scheduled. However, undergoing work is currently being performed on this direction. The implementation and application of the SEC method, which will be done within the upcoming months, will deliver an optimal strategy based on the spectroscopy signals evaluated in WP2 to optimize the extent of the charge-transfer process in a prototypical first-principles model of a OPV material.
Expected results until the end of the project: Investigations performed on WP2 will be extended to include the parametrisation of the blend environment obtained in WP1. Part of this work is already performed and final simulations to achieve this will be done in the upcoming time. These simulations will describe the charge-transfer for a more realistic model. Transient-absorption spectra will be simulated and three-pulse spectroscopies, using the existing EOM-PMA method contained in the project description. The effect of chirped pulses will be investigated, as performed in the previous work (ready for submission), which will demonstrate how tailored pulses can be used to manipulate the charge-transfer process. Last, the SEC strategy remains to be addressed. Due to the ambitious character of the project, the development of the SEC approach has not been able to be performed during the 2021-2023 period of the project, originally scheduled. However, undergoing work is currently being performed on this direction. The implementation and application of the SEC method, which will be done within the upcoming months, will deliver an optimal strategy based on the spectroscopy signals evaluated in WP2 to optimize the extent of the charge-transfer process in a prototypical first-principles model of a OPV material.