Saqib Rafique

Stability enhancement in organic solar cells by incorporating V2O5 nanoparticles in the hole transport layer

The synthesis of vanadium pentaoxide (V2O5) nanoparticles by a hydrothermal method and their utilization in a PEDOT:PSS buffer layer in a PCDTBT:PC71BM device structure is demonstrated. V2O5 nanoparticles were dispersed in the PEDOT:PSS hole transport layer (HTL) in normal architecture bulk heterojunction (BHJ) solar cells. The device performance for both pure PEDOT:PSS and hybrid HTLs were studied and demonstrated to effectively work in bulk heterojunction organic solar cells (BHJ OSCs). From the stability test initially for one week and subsequently for another three weeks, it was confirmed that the OSC device with the incorporation of V2O5 nanoparticles in the standard HTL leads to a decrease in device degradation and significantly improves the lifetime as compared to the standard HTL based device. Moreover, the hybrid HTL exhibits better optical properties and a relatively stable band gap as compared to its pristine PEDOT:PSS counterpart. Our results indicate that V2O5 could be a simple addition into the PEDOT:PSS layer to overcome its stability and degradation issues leading to an effective HTL in BHJ OSCs.

Significantly improved photovoltaic performance in polymer bulk heterojunction solar cells with graphene oxide /PEDOT:PSS double decked hole transport layer

This work demonstrates the high performance graphene oxide (GO)/PEDOT:PSS doubled decked hole transport layer (HTL) in the PCDTBT:PC71BM based bulk heterojunction organic photovoltaic device. The devices were tested on merits of their power conversion efficiency (PCE), reproducibility, stability and further compared with the devices with individual GO or PEDOT:PSS HTLs. Solar cells employing GO/PEDOT:PSS HTL yielded a PCE of 4.28% as compared to either of individual GO or PEDOT:PSS HTLs where they demonstrated PCEs of 2.77 and 3.57%, respectively. In case of single GO HTL, an inhomogeneous coating of ITO caused the poor performance whereas PEDOT:PSS is known to be hygroscopic and acidic which upon direct contact with ITO reduced the device performance. The improvement in the photovoltaic performance is mainly ascribed to the increased charge carriers mobility, short circuit current, open circuit voltage, fill factor, and decreased series resistance. The well matched work function of GO and PEDOT:PSS is likely to facilitate the charge transportation and an overall reduction in the series resistance. Moreover, GO could effectively block the electrons due to its large band-gap of ~3.6 eV, leading to an increased shunt resistance. In addition, we also observed the improvement in the reproducibility and stability.

Binary nanocomposite based on Co3O4 nanocubes and multiwalled carbon nanotubes as an ultrasensitive platform for amperometric determination of dopamine

AbstractComposites containing cobalt oxide (Co3O4) nanocubes integrated with multiwall carbon nanotubes (MWCNT) were synthesized by a hydrothermal route. The fractions of MWCNTs in the composite were varied from 4, 8, 12, 16 and 20 wt.%, and the resulting materials are denoted as C1, C2, C3, C4 and C5, respectively. The formation of products with high structural crystallinity was confirmed by X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray diffraction. A morphological study by field emission scanning electron microscopy and high resolution transmission electron microscopy showed the successful integration of Co3O4 nanocubes to the MWCNTs with an average particle size of ∼32 nm. The surface of a glassy carbon electrode (GCE) was modified with the nanocomposites in order to evaluate the electrochemical performance of the nanocomposites. Cyclic voltammetry showed that the C4-modified GCE displays best performance in terms of oxidation potential and peak current in comparison to that of a bare GCE, Co3O4 nanocubes, or GCEs modified with C1, C2, C3 or C5. The detection limit (at an S/N ratio of 3) is 0.176 nM by using chronoamperometry, and the linear range is between 1 and 20 μM. Graphical abstractMWCNT-Co3O4 nanocubes were synthesized by one pot hydrothermal route. The nanocomposite is used for electrochemical detection of dopamine. The limit of detection is found to be 176 nM by chronoamperometry at a constant potential of + 0.13 V.