Device physics and operation of lateral bulk heterojunction devices

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Lateral bulk heterojunction (BHJ) devices offer a novel approach to characterizing charge transport and recombination in organic photovoltaic (OPV) materials.
• Understanding these properties is crucial for improving OPV device efficiency and stability.

Purpose of the Study:

• To numerically simulate and experimentally verify different charge transport regimes in lateral BHJ devices.
• To investigate the lateral extents of space charge regions and their relationship to carrier drift lengths.
• To determine the mechanism of bimolecular recombination in OPV materials.

Main Methods:

• Numerical simulations to model charge transport within lateral BHJ structures.
• Confocal microscopy and steady-state current-voltage measurements on nanofabricated devices.
• Analysis of space charge region extents and recombination mechanisms.

Main Results:

• Three distinct charge transport regimes were identified in lateral BHJ devices.
• Experimental results confirmed simulation findings, with space charge regions measuring approximately 1-5 μm.
• Bimolecular recombination was confirmed as an intrinsic bulk material property.

Conclusions:

• Lateral BHJ devices provide valuable insights into in-plane charge transport and recombination in OPV films.
• These findings complement traditional vertical-device measurements.
• The developed methods enable a more comprehensive characterization of OPV material properties.