Study on the polymer solar cells with thermally stable $TiO_x$ protecting layer

Abstract

Photovoltaic devices based on polymer materials for renewable electrical power and sustainable energy have been the target of research worldwide and substantial progress in numerous aspects. There are many advantages of polymer solar cells such as low cost, light weight, large area, mechanical flexibility and easy to processability. The aforementioned factors influence the efficiency of photovoltaic cells, the absorption spectrum of the active layer, the morphology, donor and acceptor’s HOMO and LUMO level, film morphologies, charge carrier mobility and the work functions of electrodes. Also the performance of polymer solar cells has been improved by using new materials and new structure in devices. The impact of incorporation of a $TiO_x$ interlayer prepared from a newly designed precursor between the active layer of a polymer solar cell and an Al electrode is reported here. Devices with the $TiO_x$ interlayer prepared from the polymeric precursor shows greatly enhanced thermal stability compared to those with a $TiO_x$ interlayer prepared from titanium isopropoxide, which current the most widely employed precursor for the interlayer. This is attributed to the $TiO_x$ interlayer prepared from the polymeric precursor has relatively fewer reactive sites and undergoing a small morphological change during operation at high temperature, thus resulting in reduced interfacial destruction between Al and the active layer. Hence, it is possible to obtain enhanced cell performance with the $TiO_x$ layer from the polymeric precursor even at high temperature.