Ruddlesden–Popper (RP) phase metal halide organo perovskites are being extensively studied due to their quasi-two dimensional (2D) nature which makes them an excellent material for several optoelectronic device applications such as solar cells, photo-detectors, light emitting diodes (LEDs), lasers etc. While most of reports show use of linear carbon chain based organic moiety, such as n-Butylamine, as organic spacer in RP perovskite crystal structure, here we report a new series of quasi 2D perovskites with a ring type cyclic carbon group as organic spacer forming RP perovskite of type (CH)2(MA)n−1PbnI3n+1; CH = 2-(1-Cyclohexenyl)ethylamine; MA = Methylamine). This work highlights the synthesis, structural, thermal, optical and optoelectronic characterizations for the new RP perovskite series n = 1–4. The demonstrated RP perovskite of type for n = 1–4 have shown formation of highly crystalline thin films with alternate stacking of organic and inorganic layers, where the order of PbI6 octahedron layering are controlled by n-value, and shown uniform direct bandgap tunable from 2.51 eV (n = 1) to 1.92 eV (n = 4). The PL lifetime measurements supported the fact that lifetime of charge carriers increase with n-value of RP perovskites [154 ps (n = 1) to 336 ps (n = 4)]. Thermogravimetric analysis (TGA) showed highly stable nature of reported RP perovskites with linear increase in phase transition temperatures from 257 °C (n = 1) to 270 °C (n = 4). Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) are used to investigate the surface morphology and elemental compositions of thin films. In addition, the photodetectors fabricated for the series using (CH)2(MA)n−1PbnI3n+1 RP perovskite as active absorbing layer and without any charge transport layers, shown sharp photocurrent response from 17 nA/cm2 for n = 1 to 70 nA/cm2 for n = 4, under zero bias and low power illumination conditions (470 nm LED, 1.5 mW/cm2). Furthermore, for lowest bandgap RP perovskite n = 4, (CH)2MA3Pb4I13 the photodetector showed maximum photocurrent density of ~ 508 nA/cm2 at 3 V under similar illumination condition, thus giving fairly large responsivity (46.65 mA/W). Our investigations show that 2-(1-Cyclohexenyl)ethylamine based RP perovskites can be potential solution processed semiconducting materials for optoelectronic applications such as photo-detectors, solar cells, LEDs, photobatteries etc.

Success in photovoltaic power generation has raised a huge possibility in metal halide perovskites to exhibit excellent photodetection performance with the same physics of photocarrier generation, and their collection at terminal electrodes is employable with less defect-assisted carrier recombination loss. To test this, nanostructured Ruddlesden–Popper (RP)-layered perovskite series were synthesized based on a cyclic organic moiety and Br– halide, resulting in (CH)2(MA) n−1Pb n Br3n+1 [where CH2-(1-cyclohexenyl) ethylamine, MAmethylammonium, Brbromine, and n = 1–4], to explore how best its mono-to-few layer (n) 2D and quasi 2D-structures can offer photodetection performance with maximum absorbance in the unexplored blue-to-green band gap RP perovskites with maximum stability. Thermogravimetric analysis revealed that the very stable nature of these RP perovskites is accompanied by a linear rise in the structural phase transition temperatures, which range from 270 °C (CH)2PbBr4 (n = 1) to 304 °C (CH)2(MA)3Pb4Br13. The RP perovskites (CH)2(MA) n−1Pb n Br3n+1 (n = 1–4) demonstrated sharp exciton emission peaks from blue (∼408 nm) to green (∼528 nm). The X-ray diffraction results confirmed the highly crystalline nature of quasi-2D perovskite thin films. Layer-dependent photoluminescence studies exhibit strong room-temperature exciton photoluminescence and high carrier lifetime. The transient photocurrent measurements for (CH)2(MA)3Pb4Br13 (n = 4) RP perovskite thin films show nearly six times the bias voltage changed from 1 to 5 V at 405 nm laser light excitation. In addition, with respect to performance, the (CH)2(MA)3Pb4Br13 photodetector has shown the highest responsivity (67.2 mA/W), ultrafast transient photocurrent response (122 nA), and high EQE (20.6%) as compared to (CH)2(MA)2Pb3Br10 (n = 3) and (CH)2(MA)Pb2Br7 (n = 2) in ambient temperature.

This study reports overall improvement in structural, morphological, and optoelectronic properties of Ruddlesden-Popper (RP) perovskites of type (BA) 2 (MA) n−1 Pb n I 3n+1 by forming their bulk heterojunction hybrids with fewlayer MoS 2 nanoflakes. RP perovskite-MoS 2 hybrid thin films have shown significantly improved packing and crystallinity compared to pristine perovskites. The presence of MoS 2 at RP perovskite interface has improved the quantum confinement effects and transport of photogenerated charge carriers from perovskite to MoS 2 , due to suitable conduction band of MoS 2 and more number of decay channels. The optoelectronic properties of RP perovskite-MoS 2 hybrids are studied for various MoS 2 concentrations (4.2-25.6 × 10 −3 m) and at optimum concentration (12.8 × 10 −3 m) the photodetectors (n = 2, 4) have shown strong, sharp, and highly stable photocurrent response. At 0.0 V bias, the RP perovskite (n = 4) and MoS 2 (12.8 × 10 −3 m) hybrid-based photodetectors, prepared without any encapsulation, have shown strong photocurrent density of ≈9.8 µA cm −2 under 1 sun illumination, which is ≈17 times higher compared to the pristine RP perovskites-based photodetector (0.6 µA cm −2 ). Further transient photocurrent, performed over 200 cycles for hybrid (n = 4+MoS 2 ) thin film photodetector under laser (λ ex ≈ 405 nm, ≈630 mW cm −2 ) illumination and ambient air conditions has shown highly stable photocurrent with only ≈9.6% reduction in the peak photocurrent density.

The debutanizer column control is a major economic incentive to a refinery owing to the importance of the product quality. The non-linear model-based multivariable control on a debutanizer has been shown to provide improved control performance of the top product and the bottom stream qualities using a steady-state process model with approximate dynamics. The control performance is much better than that achieved by the traditional PID-type control system. This chapter outlines the non-linear control method applied to an industrial debutanizer and discusses the use of inferential models to predict the iso-pentane contents in the overhead stream and the Reid vapour pressure in the bottom stream, in non-linear control applications. R. M. Ansari et al., Nonlinear Model-based Process Control © Springer-Verlag London Limited 2000 60 Non-linear Model-based Process ControlThe use of this type of model to predict the control action required to meet the control objectives can be expected to provide improved performance over simple, linear models. In addition, for multiple-inputlmultiple-output (MIMO) systems, the model accounts for interaction among the process variables. Therefore, the model can predict the control actions to move all the controlled variables towards setpoint while the single loops may interact with each other.It is the non-linearities of the process model that provide the improved performance, therefore any controller structure developed must preserve these nonlinearities. The generic model control (GMC) structure of Lee and Sullivan (1988) permits the direct use of non-linear dynamic models and, therefore, provides the basic structure of the model-based controller. Since the GMC imbeds a mechanistic process model within the control strategy, it makes sense that this model could also be used for on-line optimization of the process. In this chapter, the GMC structure is further extended to permit the use of steady-state non-linear models in conjunction with estimates of the true process dynamics.There are a number of control strategies based on using a non-linear approximate model directly for control decisions. Economou et al. (1986) extended the internal model control so that non-linear model can be used. This approach is called the non-linear internal model control (NLIMC) and uses an iterative integration of the approximate model for its control law. Riggs and Rhinehart (1988) compared the GMC and the NLIMC for a wide range of exothermic CSTR control problems and exchanger control problems and found that both methods gave essentially the same control performance. They pointed out that the GMC control law is an explicit numerical formulation while the NLIMC is an implicit one so that the GMC is considerably easier to implement and requires less computational effort.Parrish and Brasilow (1988) used non-linear predictive model control (NLPMC), by taking into consideration the internal model structure but assigned any process/model mismatch to unmeasured disturbances. Bequette (1988) presented a version...