Charge Transport in Imperfect Organic Field Effect Transistors: Effects of Charge Traps

Monte Carlo simulations were used to study the effects of explicit charge traps on charge transport in small-molecule organic field effect transistors. The results show that the source-drain current decreases as the trap/barrier concentration increases, reaches a minimum around 30/70%, and increases as the concentration reaches 100%, regardless of the trap/barrier distribution. Greater current is predicted for heterogeneous trap distributions than for homogeneous trap distributions, due to wider conduction pathways that allow for more charge carriers to reach the drain electrode. Also, the distributions of distances and potential energy between charge carriers and trap sites were shown to depend on the heterogeneity of the traps and device geometry and, in most cases, are non-Gaussian in shape, due to electrostatic effects between charged traps, unlike previous assumptions. For some ranges of heterogeneity, these densities of states exhibit exponential tails. These results suggest that more experimental work is needed to gain insight into the energetic density of states under operating conditions in electronic devices made from mixed films of organic semiconductors, such as solar cells

Charge Transport in Imperfect Organic Field Effect Transistors: Effects of Charge Traps

Monte Carlo simulations were used to study the effects of explicit charge traps on charge transport in small-molecule organic field effect transistors. The results show that the source-drain current decreases as the trap/barrier concentration increases, reaches a minimum around 30/70%, and increases as the concentration reaches 100%, regardless of the trap/barrier distribution. Greater current is predicted for heterogeneous trap distributions than for homogeneous trap distributions, due to wider conduction pathways that allow for more charge carriers to reach the drain electrode. Also, the distributions of distances and potential energy between charge carriers and trap sites were shown to depend on the heterogeneity of the traps and device geometry and, in most cases, are non-Gaussian in shape, due to electrostatic effects between charged traps, unlike previous assumptions. For some ranges of heterogeneity, these densities of states exhibit exponential tails. These results suggest that more experimental work is needed to gain insight into the energetic density of states under operating conditions in electronic devices made from mixed films of organic semiconductors, such as solar cells

Charge Transport in Imperfect Organic Field Effect Transistors: Effects of Charge Traps

Monte Carlo simulations were used to study the effects of explicit charge traps on charge transport in small-molecule organic field effect transistors. The results show that the source-drain current decreases as the trap/barrier concentration increases, reaches a minimum around 30/70%, and increases as the concentration reaches 100%, regardless of the trap/barrier distribution. Greater current is predicted for heterogeneous trap distributions than for homogeneous trap distributions, due to wider conduction pathways that allow for more charge carriers to reach the drain electrode. Also, the distributions of distances and potential energy between charge carriers and trap sites were shown to depend on the heterogeneity of the traps and device geometry and, in most cases, are non-Gaussian in shape, due to electrostatic effects between charged traps, unlike previous assumptions. For some ranges of heterogeneity, these densities of states exhibit exponential tails. These results suggest that more experimental work is needed to gain insight into the energetic density of states under operating conditions in electronic devices made from mixed films of organic semiconductors, such as solar cells

Charge Transport in Imperfect Organic Field Effect Transistors: Effects of Charge Traps

Monte Carlo simulations were used to study the effects of explicit charge traps on charge transport in small-molecule organic field effect transistors. The results show that the source-drain current decreases as the trap/barrier concentration increases, reaches a minimum around 30/70%, and increases as the concentration reaches 100%, regardless of the trap/barrier distribution. Greater current is predicted for heterogeneous trap distributions than for homogeneous trap distributions, due to wider conduction pathways that allow for more charge carriers to reach the drain electrode. Also, the distributions of distances and potential energy between charge carriers and trap sites were shown to depend on the heterogeneity of the traps and device geometry and, in most cases, are non-Gaussian in shape, due to electrostatic effects between charged traps, unlike previous assumptions. For some ranges of heterogeneity, these densities of states exhibit exponential tails. These results suggest that more experimental work is needed to gain insight into the energetic density of states under operating conditions in electronic devices made from mixed films of organic semiconductors, such as solar cells

Improved Scaling of Molecular Network Calculations: The Emergence of Molecular Domains

The design of materials needed for the storage, delivery, and conversion of (re)­useable energy is still hindered by the lack of new, hierarchical molecular screening methodologies that encode information on more than one length scale. Using a molecular network theory as a foundation, we show that to describe charge transport in disordered materials the network methodology must be scaled-up. We detail the scale-up through the use of adjacency lists and depth first search algorithms for during operations on the adjacency matrix. We consider two types of electronic acceptors, perylenediimide (PDI) and the fullerene derivative phenyl-C61-butyric acid methyl ester (PCBM), and we demonstrate that the method is scalable to length scales relevant to grain boundary and trap formations. Such boundaries lead to a decrease in the percolation ratio of PDI with system size, while the ratio for PCBM remains constant, further quantifying the stable, diverse transport pathways of PCBM and its success as a charge-accepting material