The properties of layered inorganic semiconductors can be manipulated by the insertion of foreign molecular species via a process known as intercalation. In the present study, we investigate the phenomenon of organic moiety (R-NH3I) intercalation in layered metal-halide (PbI2)-based inorganic semiconductors, leading to the formation of inorganic–organic (IO) perovskites [(R-NH3)2PbI4]. During this intercalation strong resonant exciton optical transitions are created, enabling study of the dynamics of this process. Simultaneous in situ photoluminescence (PL) and transmission measurements are used to track the structural and exciton evolution. On the basis of the experimental observations, a model is proposed which explains the process of IO perovskite formation during intercalation of the organic moiety through the inorganic semiconductor layers. The interplay between precursor film thickness and organic solution concentration/solvent highlights the role of van der Waals interactions between the layers, as well as the need for maintaining stoichiometry during intercalation. Nucleation and growth occurring during intercalation matches a Johnson–Mehl–Avrami–Kolmogorov model, with results fitting both ideal and nonideal cases.

Room-temperature photocurrent measurements in two-dimensional (2D) inorganic–organic perovskite devices reveal that excitons strongly contribute to the photocurrents despite possessing binding energies over 10 times larger than the thermal energies. The p-type (C6H9C2H4NH3)2PbI4 liberates photocarriers at metallic Schottky aluminum contacts, but incorporating electron- and hole-transport layers enhances the extracted photocurrents by 100-fold. A further 10-fold gain is found when TiO2 nanoparticles are directly integrated into the perovskite layers, although the 2D exciton semiconducting layers are not significantly disrupted. These results show that strong excitonic materials may be useful as photovoltaic materials despite high exciton binding energies and suggest mechanisms to better understand the photovoltaic properties of the related three-dimensional perovskites.

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Non-contact bi-directional micropatterning of two-dimensional (2D) layered inorganic-organic (IO) perovskite [(R-NH3)2PbI4, R = organic moiety] thin films by direct laser writing (DLW) has been reported. These 2D materials are in the form of natural multiple quantum well (MQW) structures and show excitonic luminescence at room temperature because of quantum and dielectric confinement effects. Systematic optical and structural analyses of these laser processed hybrid systems provide an insight into laser-matter interaction and a pathway to develop technology to define complex 2D material based devices with new functionalities. These laser-matter interaction studies reveal several concurrent processes: single photon absorption, material ablation, melting and agglomeration of nanostructures and chemical/physical modifications. This study also provides an insight into chemical and optical changes in laser processed 2D perovskites which subsequently can be recovered by chemical processing. Apart from controllable feature sizes, the prolonged laser exposure results in material agglomeration in the form of nano-pillars at the laser track boundaries. Low-cost micro/nano-scaffolding of IO perovskites may have several important advantages in scalable optoelectronic devices, the realisation of luminescent photonic architectures (photonic crystals and waveguides), and light harvesting elements for IO LEDs and solar cells.

The infiltration of small chain alcohols into the deep nano sized pores of one dimensional porous silicon (PS) based photonic structures have been continuously monitored against time by simultaneous electrical and optical measurements. The in situ optical reflection studies during volatile solvent exposure reveal several dynamic processes; within a limited time duration of solvent exposure the microcavity resonant peak shifts towards higher wavelength, and after prolonged exposure and drying the cavity resonant peak shifts to a new semi-permanent lower wavelength. In situ optical and electrical responses from PS photonic structure-based low-cost multifunctional devices reveal their potential application for a wide range of chemical and biological species detection and monitor their sensor dynamic processes.