Orientation‐Engineered Small‐Molecule Semiconductors as Dopant‐Free Hole Transporting Materials for Efficient and Stable Perovskite Solar Cells

• Published in: Advanced functional materials 2021-05, Vol.31 (20), p.n/a
• Main Authors: Zhou, Zhiwen, Wu, Qisheng, Cheng, Rui, Zhang, Hong, Wang, Sijia, Chen, Mojun, Xie, Maohai, Chan, Paddy Kwok Leung, Grätzel, Michael, Feng, Shien‐Ping
• Format: Article
• Language: English
• Subjects: Carrier mobility; Crystallization; Dopants; dopant‐free; Hole mobility; hole transport materials; MAPbI 3 solar cells; Materials science; mobility; Molecular orbitals; molecular orientation; Orientation; P-type semiconductors; Perovskites; Photovoltaic cells; Semiconductors; Solar cells; Substrates; Transportation
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202011270

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. An organic small‐molecule semiconductor, DPh‐DNTT, can be utilized as a dopant‐free hole transporting material (HTM) for highly efficient and stable inverted perovskite solar cells due to its temperature‐dependent molecular orientation. By decreasing the deposition temperature, DPh‐DNTT films with a dominant face‐on orientation are achieved, which exhibit improved out‐of‐plane hole mobility and excellent perovskite device performance without the incorporation of double‐edged dopants.