The performance of organic solar cells is highly dependent on film morphology. However, directly correlating local film structures with device performance remains challenging. We demonstrate that photoconductive atomic force microscopy (pcAFM) can be used to map local photocurrents with 20 nm resolution in donor/acceptor blend solar cells of the conjugated polymer poly[2-methoxy-5-(3',7'-dimethyloctyl-oxy)-1,4-phenylene vinylene] (MDMO-PPV) with the fullerene (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) spin-coated from various solvents. We present photocurrent maps under short-circuit conditions (zero applied bias) as well as under various applied voltages. We find significant variation in the short-circuit current between regions that appear identical in AFM topography. These variations occur from one domain to another as well as on larger length scales incorporating multiple domains. These results suggest that the performance of polymer-fullerene blends can still be improved through better control of morphology.

We measure the potential profiles of both dynamic and fixed junction planar light-emitting electrochemical cells (LECs) using Scanning Kelvin Probe Microscopy (SKPM) and compare the results against models of LEC operation. We find that, in conventional dynamic junction LECs formed using lithium trifluoromethanesulfonate (LiTf), poly(ethylene oxide) (PEO), and the soluble alkoxy-PPV derivative poly[2-methoxy-5-(3',7'-dimethyl-octyloxy)-p-phenylenevinylene (MDMO-PPV), the majority (>90%) of the potential is dropped near the cathode with little potential drop across either the film or the anode/polymer interface. In contrast, when examining fixed junction LECs where the LiTf is replaced with [2-(methacryloyloxy)ethyl] trimethylammonium 2-(methacryloyloxy)ethane-sulfonate (METMA/MES), the potential is dropped at both contacts during the initial poling. The potential profile evolves over a period of approximately 60 min under bias to achieve a final profile similar to that obtained in the LiTf systems. In addition to elucidating the differences between conventional dynamic LECs and fixed LECs incorporating cross-linkable ion pair monomers, the results on both systems provide direct evidence for a primarily "p-type" LEC consistent with the emitting junction near the cathode and relatively small electric fields across the bulk of the device for these two material systems.

We study the operation of polymer light-emitting electrochemical cells (LECs) by combining scanning Kelvin probe microscopy with in situ imaging of the electroluminescence and photoluminescence on planar LECs. By combining these techniques on the same device in the same apparatus we directly map the relationship between the spatial distribution of electroluminescence and the local potential profile across the device. We find that the electroluminescence is always associated with a region of potential drop in LECs made with poly[2-methoxy-5-(3',7'-dimethyl-octyloxy)-p-phenylenevinylene] (MDMO-PPV), poly(ethylene oxide)(PEO), and potassium trifluoromethanesulfonate. Nevertheless, depending on the electrode metal used, we also find significant potential drops at or near the electrode/organic interfaces. We study the effects of using different electrodes and show that both the electroluminescence and potential profiles are strongly dependent on the electrode work function for thin junctions operated at low potentials. These results indicate injection barriers can affect the operation of LECs even in the presence of doping.

A p–n junction in an organic emissive polymer is chemically fixed through the use of polymerizable ions. This leads to a permanent configuration of compensating ions, unlike dynamic light‐emitting electrochemical cells. The process is demonstrated with red‐, green‐, and blue‐light‐emissive polymers; a photovoltaic effect is also demonstrated.

Charge transport measurements reveal non‐Langevin recombination for KP115:PCBM organic photovoltaic devices. This rare but highly advantageous behaviour allows a long charge carrier drift length and thus devices with thick active layers retain a high fill factor. However, no clear correlation with morphology was found, indicating that the origin of non‐Langevin recombination may be more complex than previously thought.