A multi-junction photovoltaic device comprising a layer of metal oxynitride between a first sub-cell and a second sub-cell is disclosed, the first sub-cell having a layer comprising a perovskite light absorber material. In addition, a method of manufacturing said multi junction photovoltaic device is disclosed. The metal oxynitride is preferably titanium oxynitride. Advantageously, the device may be produced in a simple, fast, consistent and inexpensive manner, whilst the properties of the titanium oxynitride layer may be tuned to avoid the occurrence of local shunt paths and to reduce reflection losses.