Efficient Top Illuminated Polymer Solar Cells with Distributed Bragg Reflector on Flexible Metal Substrate

Abstract

Thin-film solar cells such as polymer solar cells on flexible substrates are considered the most promising candidates for low-cost photovoltaic devices. Polymer solar cells have many advantages including flexible and unbreakable characteristics, cheap substrate and ease for roll-to-roll fabrication which have potential for broad applications such as energy sources for cellular phone, ID cards and clothes equipped with electronic devices. Previously, people focused on plastic film, PET/ITO film for instance, but its high water vapor permeation rate appears at a distinct disadvantage. Metal substrates like stainless steel (SS) or copper plate can solve this problem. Furthermore, those materials also attract industrial researchers because of their popular applications. However, the high rough and low transparent surface of those metal sheets is obstacle which can impact the performance of thin-film solar cells. In this work, we use a high re-flecting and insulating protective layers comprising of Distributed Bragg Reflector (DBR) to treat the surface. DBR shows high potential to reduce roughness, prevent STS sheet from oxidation during high temperature sintering process and increase the reflectance property. DBR consisting of Ta2O5 and SiO2 was carried out as the back reflector for upper polymer solar cells. Its optical and electrical properties were also examined.