No abstract

Perovskite solar cells have set a new milestone in terms of efficiencies in the thin film photovoltaics category.Long-term stability of perovskite solar cells is of paramount importance but remains a challenging task. The lack of perovskite solar cells stability in real-time operating conditions erodes and impedes commercialization.Further improvements are essential with a view to delivering longer-lasting photovoltaic (PV) performances.An ideal path in this direction will be to identify novel dopants for boosting the conductivity and hole mobility of hole transport materials (HTMs), and by so doing the usage of hygroscopic and deliquescent additive materials can be avoided. Pyridine-based ionic liquids represent a well-known class of ultra-hydrophobic materials, which are suitable for their application in opto-electrical devices. The present work demonstrates the employment of ionic liquids into a dissymmetric fluorene-dithiophene, FDT (2',7' -bis(bis(4-methoxyphenyl)amino) spiro [cyclopenta[2,1-b:3,4-b']dithiophene-4,9'-fluorene]) based HTM to understand the doping mechanisms. N-heterocyclic hydrophobic ionic liquid, 1-butyl-3-methylpyidinium bis(trifluoromethylsulfonyl)imide (BMPyTFSI) as p-type dopant for FDT was found to increase the conductivity of FDT, to higher geometrical capacitance, to facilitate homogeneous film formation, and to enhance device stability. Our findings open up a broad range of hole-transport materials to control the degradation of the underlying water-sensitive active layer by substituting hygroscopic element.File list (1) download file view on ChemRxiv Doping_NH.docx (7.62 MiB)

The combination of graphene with conductive nanoparticles, forming graphene–nanoparticle hybrid materials, offers a number of excellent properties for advanced engineering applications. A novel and simple method was developed to deposit 10 wt% tin-doped indium tin oxide (ITO) nanoparticles on graphene. The method involved a combination of a solution-based environmentally friendly electroless deposition approach and subsequent vacuum annealing. A stable organic-free solution of ITO was prepared from economical salts of In(NO3)3·H2O and SnCl4. The obtained ITO nanostructure exhibited a unique architecture, with uniformly dispersed 25–35 nm size ITO nanoparticles, containing only the crystallized In2O3 phase. The synthesized ITO nanoparticles–graphene hybrid exhibited very good and reproducible optical transparency in the visible range (more than 85%) and a 28.2% improvement in electrical conductivity relative to graphene synthesized by chemical vapor deposition. It was observed that the ITO nanoparticles affect the position of the Raman signal of graphene, in which the D, G, and 2D peaks were redshifted by 5.65, 5.69, and 9.74 cm−1, respectively, and the annealing conditions had no significant effect on the Raman signatures of graphene.

The rapid scientific surge in halide perovskite solar cells (PSCs) is owing to their solution processability and high power conversion efficiency, however, the deficiency in the photo-induced charge transfer dynamics...

Understanding the device kinetics occurring in the bulk and charge selective layers is vital for optimizing the performance of perovskite solar cells (PSCs) and their development. We studied planar PSCs with and without hole transport layer (HTL) and measured hysteresis free power conversion efficiency of 16.23% with poly(3-hexylthiophene) [P3HT] as HTL, while the PSCs without HTL showed significant hysteresis. We investigated a comprehensive electrical response of the PSCs. The bias-dependent electrochemical impedance spectroscopy (EIS) revealed the appearance of the negative capacitance in the low-frequency regime. The modification of the low-frequency PSCs response accompanied by a further decrease in recombination resistance is due to the interfacial interactions between the migrating ions and the metal contact. The doped and undoped P3HT layers impeded this interaction which explains the absence of the negative capacitance at lower applied voltages. Our investigation provides an understanding of the physical processes behind the negative capacitance.