Visualizing the Link Between Nanomorphology and Energetic Disorder in 3D Organic Solar Cells

TL;DR

This paper introduces a 3D hybrid modeling approach to study how nanomorphology and energetic disorder affect organic solar cell performance, revealing that energetic disorder hampers charge extraction even with intact pathways.

Contribution

The work presents a novel 3D hybrid model that combines morphology generation and energetic disorder effects, enabling detailed analysis of their impact on device efficiency.

Findings

Energetic disorder limits charge extraction despite percolation pathways.

Nanoscale molecular packing is as important as mesoscale phase separation.

The model can operate at high carrier densities and include energetic disorder effects.

Abstract

The performance of organic bulk heterojunction (BHJ) solar cells is highly sensitive to both nanomorphology and energetic disorder arising from microscopic molecular packing and structural defects. However, most models used to understand these devices are either one-dimensional effective medium approximations that neglect spatial and energetic disorder or three-dimensional Monte Carlo simulations that are computationally intensive. In this work, we present the results from a three-dimensional hybrid model capable of operating at both high carrier densities and incorporating the effects of energetic disorder. We first generate realistic morphologies using a phase-field approach that accounts for solvent evaporation during film formation. Using these example morphologies, we systematically study the interplay between energetic disorder and configurational disorder at carrier densities representative of real device operation. This enables us to separate and visualize the impact of the nanomorphology and energetic disorder on device performance. Our results reveal that, even when macroscopic percolation pathways remain intact, energetic disorder limits performance primarily through suppressed charge extraction in interconnected domains. This suggest that optimizing molecular packing at the nanoscale is as critical as controlling phase separation at the mesoscale, highlighting the need for multiscale design strategies in next-generation BHJ devices.