| Affiliation: | 1. Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Station 6, Lausanne, CH-1015 Switzerland;2. Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI, 48824 USA;3. Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China;4. Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Station 6, Lausanne, CH-1015 Switzerland;5. Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China |
| Abstract: | Crystallized p-type small-molecule semiconductors have great potential as an efficient and stable hole transporting materials (HTMs) for perovskite solar cells (PSCs) due to their relatively high hole mobility, good stability, and tunable highest occupied molecular orbitals. Here, a thienoacene-based organic semiconductor, 2,9-diphenyldinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DPh-DNTT), is thermally evaporated and employed as the dopant-free HTM that can be scaled up for large-area fabrication. By controlling the deposition temperature, the molecular orientation is modulated into a dominant face-on orientation with π–π stacking direction perpendicular to the substrate surface, maximizing the out-of-plane carrier mobility. With an engineered face-on orientation, the DPh-DNTT film shows an improved out-of-plane mobility of 3.3 × 10−2 cm2 V−1 s−1, outperforming the HTMs reported so far. Such orientation-reinforced mobility contributes to a remarkable efficiency of 20.2% for CH3NH3PbI3 inverted PSCs with enhanced stability. The results reported here provide insights into engineering the orientation of molecules for the dopant-free organic HTMs for PSCs. |
