This article reviews recently published work concerning improved understanding of, and advancements in, organic and polymer semiconductor vapor-phase chemical sensing. Thin-film transistor sensors ranging in size from hundreds of microns down to a few nanometers are discussed, with comparisons made of sensing responses recorded at these different channel-length scales. The vapor-sensing behavior of nanoscale organic transistors is different from that of large-scale devices, because electrical transport in a nanoscale organic thin-film transistor depends on its morphological structure and interface properties (for example injection barrier) which could be modulated by delivery of analyte. Materials used in nanoscale devices, for example nanoparticles, nanotubes, and nanowires, are also briefly summarized in an attempt to introduce other relevant nano-transducers.

The organic carrier-selective layer, poly­(3,4-ethylenedioxythiophene):poly­(styrene sulfonate) (PEDOT:PSS) coated on Si wafers, has attracted a lot of attention toward the development of low-cost and efficient hybrid solar cells (HSCs). Here, highly efficient PEDOT:PSS/Si HSCs are reported via an effective surface microengineering of the as-cut, low-cost solar-grade thin Si wafers, an aspect rarely addressed before, by a simple one-step aqueous KOH process. The influence of surface microstructuring on their light harvesting properties, polymer/Si junction formation, and photovoltaic (PV) performance of the PEDOT:PSS/Si HSCs are investigated. The simple one-step process under the optimized processing conditions reduces the weighted surface reflectivity from >35 to <9% in a broad spectral range in addition to removing the surface saw damages of the wafers completely. The combined effect in turn improves the PEDOT:PSS/Si interface (junction) property, leading to a highly efficient PEDOT:PSS/Si HSC even in its simplest possible device structure. Moreover, the antireflective and surface passivation properties of the PEDOT:PSS layer for the microstructured Si surfaces are also demonstrated. The optimized microsurface and cell processing conditions resulted in the HSCs with a photoconversion efficiency >12.25%, which is absolute ∼9.70% (∼5 folds) higher when compared to that on starting non-structured Si wafers. The results are further supported by detailed dark J–V characteristics and quantum efficiency analysis of the devices. The study establishes that microengineering of the commercial as-cut Si wafers removes the surface damages on both sides which if not addressed properly cause very high surface recombination losses and have a detrimental effect on the polymer/Si junction and hence the PV performances. The study paves the way to develop simple yet efficient HSCs on such economic solar-grade Si wafers commonly used for the conventional Si solar cells.

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