Using a facile processing method to facilitate charge extraction for polymer solar cells

Abstract

It is necessary to carefully adjust the interface characteristics between the interlayer and active layer in order to facilitate charge extraction and transfer. Here, a post-annealing treatment on the completed device with a Ag electrode is used to optimize the interface contact characteristics between WO₃ and the active layer due to the inter-diffusion of the WO₃ hole-extraction interface. The strengthened interface contact between them can improve the charge extraction and transfer across the active layer/WO₃ interface. Furthermore, a thinner WO₃ interlayer (75 Å) is shown to qualify as an anode interlayer with excellent charge selection, extraction and transport capacities after the post-annealing treatment, which is beneficial for reducing the resistance loss introduced by the too thick WO₃ layer and enhancing device performance. As a result, the device with the 75 Å WO₃ layer and 60 °C post-annealing treatment provides a higher fill factor of 74.5% and an optimal device performance of 9.66%. This work reveals a simple and universal method to modulate the interface contact characteristics between an evaporated transition metal oxide interlayer and an active layer, thus improving the device performance.