Hybrid organic–inorganic perovskites have recently gained immense attention due to their unique optical and electronic properties and low production cost, which make them promising candidates for a wide range of optoelectronic devices. But unlike most other technologies, the breakthroughs witnessed in hybrid perovskite optoelectronics have outgrown the basic understanding of the fundamental material properties. For example, the effectiveness of charge transport in relation to film microstructure and processing has remained elusive. In this study, field‐effect transistors are fabricated and evaluated in order to probe the nature and dynamics of charge transport in thin films of methylammonium lead iodide. A dramatic improvement is shown in the electrical properties upon solvent vapor annealing. The resulting devices exhibit ambipolar transport, with room‐temperature hole and electron mobilities exceeding 10 cm2V−1s−1. The remarkable enhancement in charge carrier mobility is attributed to the increase in the grain size and passivation of grain boundaries via the formation of solvent complexes.
Polymorphism, the ability for a given material to adopt multiple crystalline packing states, is a powerful approach for investigating how changes in molecular packing influence charge transport within organic semiconductors. In this study, a new “thin film” polymorph of the high‐performance, p‐type small molecule N‐octyldiisopropylsilyl acetylene bistetracene (BT) is isolated and characterized. Structural changes in the BT films are monitored using static and in situ grazing‐incidence X‐ray diffraction. The diffraction data, combined with simulation and crystallographic refinement calculations, show the molecular packing of the “thin film” polymorph transforms from a slipped 1D π‐stacking motif to a highly oriented and crystalline film upon solvent vapor annealing with a 2D brick‐layer π‐stacking arrangement, similar to the so‐called “bulk” structure observed in single crystals. Charge transport is characterized as a function of vapor annealing, grain orientation, and temperature. Demonstrating that mobility increases by three orders of magnitude upon solvent vapor annealing and displays a differing temperature‐dependent mobility behavior.
more » « less- PAR ID:
- 10053663
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Interfaces
- Volume:
- 5
- Issue:
- 9
- ISSN:
- 2196-7350
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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