Limits...
Role of coherence and delocalization in photo-induced electron transfer at organic interfaces

View Article: PubMed Central - PubMed

ABSTRACT

Photo-induced charge transfer at molecular heterojunctions has gained particular interest due to the development of organic solar cells (OSC) based on blends of electron donating and accepting materials. While charge transfer between donor and acceptor molecules can be described by Marcus theory, additional carrier delocalization and coherent propagation might play the dominant role. Here, we describe ultrafast charge separation at the interface of a conjugated polymer and an aggregate of the fullerene derivative PCBM using the stochastic Schrödinger equation (SSE) and reveal the complex time evolution of electron transfer, mediated by electronic coherence and delocalization. By fitting the model to ultrafast charge separation experiments, we estimate the extent of electron delocalization and establish the transition from coherent electron propagation to incoherent hopping. Our results indicate that even a relatively weak coupling between PCBM molecules is sufficient to facilitate electron delocalization and efficient charge separation at organic interfaces.

No MeSH data available.


Related in: MedlinePlus

Radial distribution of (e-h) separation distance at early times.The shaded grey area indicates the position of the donor site. Dashed red line represents the exponential character of the e-h distance distribution after 800 fs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5015064&req=5

f3: Radial distribution of (e-h) separation distance at early times.The shaded grey area indicates the position of the donor site. Dashed red line represents the exponential character of the e-h distance distribution after 800 fs.

Mentions: Figure 3 shows the temporal evolution of e-h distance distribution without external electric field in the intermediate coupling regime. The electron gets completely transferred from the donor site to the acceptor lattice in ~500 fs, however, it is still strongly bound to the hole. Further charge separation is facilitated by incoherent electron hopping as outlined in ref. 17. The resulting e-h distance distribution at 800 fs can be approximated as an exponential (red dashed line in Fig. 3) and could be used in classical hopping models as the initial distribution.


Role of coherence and delocalization in photo-induced electron transfer at organic interfaces
Radial distribution of (e-h) separation distance at early times.The shaded grey area indicates the position of the donor site. Dashed red line represents the exponential character of the e-h distance distribution after 800 fs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5015064&req=5

f3: Radial distribution of (e-h) separation distance at early times.The shaded grey area indicates the position of the donor site. Dashed red line represents the exponential character of the e-h distance distribution after 800 fs.
Mentions: Figure 3 shows the temporal evolution of e-h distance distribution without external electric field in the intermediate coupling regime. The electron gets completely transferred from the donor site to the acceptor lattice in ~500 fs, however, it is still strongly bound to the hole. Further charge separation is facilitated by incoherent electron hopping as outlined in ref. 17. The resulting e-h distance distribution at 800 fs can be approximated as an exponential (red dashed line in Fig. 3) and could be used in classical hopping models as the initial distribution.

View Article: PubMed Central - PubMed

ABSTRACT

Photo-induced charge transfer at molecular heterojunctions has gained particular interest due to the development of organic solar cells (OSC) based on blends of electron donating and accepting materials. While charge transfer between donor and acceptor molecules can be described by Marcus theory, additional carrier delocalization and coherent propagation might play the dominant role. Here, we describe ultrafast charge separation at the interface of a conjugated polymer and an aggregate of the fullerene derivative PCBM using the stochastic Schrödinger equation (SSE) and reveal the complex time evolution of electron transfer, mediated by electronic coherence and delocalization. By fitting the model to ultrafast charge separation experiments, we estimate the extent of electron delocalization and establish the transition from coherent electron propagation to incoherent hopping. Our results indicate that even a relatively weak coupling between PCBM molecules is sufficient to facilitate electron delocalization and efficient charge separation at organic interfaces.

No MeSH data available.


Related in: MedlinePlus