Bicontinuous minimal surface nanostructures for polymer blend solar cells

Abstract

This paper presents the first examination of the potential for bicontinuous structures such as the gyroid structure to produce high efficiency solar cells based on conjugated polymers. The solar cell characteristics are predicted by a simulation model that shows how the morphology influences device performance through integration of all the processes occurring in organic photocells in a specified morphology. In bicontinuous phases, the surface defining the interface between the electron and hole transporting phases divides the volume into two disjoint subvolumes. Exciton loss is reduced because the interface at which charge separation occurs permeates the device so excitons have only a short distance to reach the interface. As each of the component phases is connected, charges will be able to reach the electrodes more easily. In simulations of the current-voltage characteristics of organic cells with gyroid, disordered blend and vertical rod (rods normal to the electrodes) morphologies, we find that gyroids have a lower than anticipated performance advantage over disordered blends, and that vertical rods are superior. These results are explored thoroughly, with geminate recombination, i.e. recombination of charges originating from the same exciton, identified as the primary source of loss. Thus, if an appropriate materials choice could reduce geminate recombination, gyroids show great promise for future research and applications.

Suppression of geminate charge recombination in organic photovoltaic devices with a cascaded energy heterojunction

“…In The reason for the strong d dependence of charge separation efficiency can be explained by the observation that geminate charges prior to recombination or separation typically have small separations due to mutual Coulomb interaction 51,52 . Hence, the charge transport environment more than ~5nm distant from the donor-acceptor interface 51 is typically only explored by charges that are en-route to charge separation.…”

A multiscale modeling study of loss processes in block-copolymer-based solar cell nanodevices

“…48 In the previous equation, E C ij represents the energy difference between the Coulombic interaction energies of the charges at site j and i with all other charges within a cutoff, 49 i.e.,…”

Simulating charge transport in organic semiconductors and devices: a review

“…As well as bilayers [73,143,377], morphologies examined include interdigitated pillars [48,201,[378][379][380], gyroids [381], idealised BHJs [48, 147,201,380] and non-ideal BHJs [114,123,382,383]. It is shown that interdigitated pillars have highest performance, since the electric field is either parallel or perpendicular to the plane of the heterojunction, while perhaps unexpectedly, gyroid and idealised BHJ morphologies have very similar performance [381]. However, since interdigitated OPVs are laborious to fabricate [384], we focus our attention on the impact of non-ideal (i.e.…”