Analysis of photocurrents in lateral-geometry organic bulk heterojunction devices

Lateral-geometry organic bulk heterojunction (BHJ) devices resemble field-effect transistors without a gate and are useful for probing electrical characteristics of BHJ blends. The lateral structure allows physical access to the BHJ during device operation and lends itself well to device modelling. Photocurrent-voltage data from P3HT:PCBM-based lateral devices were found to possess features of space-charge limited (SCL) extraction. Numerical simulations indeed suggest a physical picture of SCL operation, effectively dividing the device into a photogenerative zone and a photoconducting zone. Based on these simulations, an analytical model was created to describe SCL photocurrents that account for channel lengths and bimolecular recombination.