1. Department of Chemical Engineering Molecular Engineering and Sciences Institute University of Washington Seattle WA 98195‐1652 USA
2. Laboratory of Photonics and Interfaces (LPI) École Polytechnique Fédérale de Lausanne (EPFL) Lausanne 1015 Switzerland
3. Department of Materials Science and Engineering University of Washington Seattle WA 98195‐2120 USA
4. Laboratory for Thin Films and Photovoltaics Empa – Swiss Federal Laboratories for Materials Science and Technology 8600 Dübendorf Switzerland
5. Department of Materials Science and Engineering Department of Chemistry City University of Hong Kong Kowloon 999077 Hong Kong