Functionalized Thermoplastic Polyurethane as Hole Conductor for Quantum Dot-Sensitized Solar Cell

Abstract

A hole conducting layer for quantum dot sensitized solar cell (QDSS) as a function of redox behavior has been reported. Polyurethanes, comprising hard and soft segments, have been functionalized for its use in solar cell application. Functionalization has been confirmed through NMR and FTIR studies. The functionalization of hard segment results in incorporation of ionic moieties which enhances its electrical conductivity, electrochemical and optical properties and displays a crucial role as a hole transport materials for QDSS cells due to proper work function and reduces energy barrier at the interface of active layer and counter electrode leading to reversible charge transport without decomposition. Cadmium sulfide (CdS) quantum dot has been synthesized using capping agent and the size (4 nm) and shape (spherical) has been confirmed through various techniques, including TEM, AFM, SEM, and DLS. Energy diagram of whole system has been revealed by measuring HOMO–LUMO and VB–CB energy gap through cyclic voltammetry and UV–vis spectrophotometry. The proper energy level alignment with electron transport layer and electron collecting layer provides suitability to transport hole for continuous harvesting of light. Solar cell device has been fabricated using successful layered design of functionalized polyurethane. The incorporation of a thin polyaniline (PANi) layer helps reducing the electron transport toward reverse direction (cathode) by adjusting the LUMO energy gap of polymer gel electrolyte and confirms re-excitation of dropped electron toward quantum dots (photoanode) through quenching under continuous illumination. The device with structure FTO/TiO2/CdS/PANi/PGE/Pt exhibits a photocurrent density of (J sc ∼ 2.20 mA/cm2), open circuit voltage V oc of 0.60 V, fill factor of 0.78 and photovoltaic conversion efficiency (PCE) of 1.25% using functionalized polyurethane.

Functionalized polythiophene for corrosion inhibition and photovoltaic application

“…Cyclic voltammetry (CV) is an effective technique to investigate the electrochemical properties of the materials such as redox behavior of polymers. CV measures the current resulting from an applied potential with a fixed scan rate (mV s −1 ) 60,59 . Oxidation produces positively charged species while reduction makes a polymer chain negatively charged during redox reaction.…”

Functionalized polyurethane composite gel electrolyte with cosensitized photoanode for higher solar cell efficiency using a passivation layer

“…Synthesis of GO-tagged polyurethane. Polymer synthesis was carried out in three stages of polymerization process 32,33,43 with some alteration. In a typical PU-GO polymer synthesis, the rst step involved the formation of prepolymer (PP) by mixing the poly(tetramethylene glycol) (PTMG) and 4,4 0 -methylene diphenyldiisocyanate in dimethylformamide solvent at 70 C in the presence of nitrogen atmosphere for 3 h to form an isocyanateterminated prepolymer.…”

“…chains. The functionalized polymer (SPU-GO) shows a new strong peak at a chemical shi of d ¼ 8.48 ppm for -SO 3 H proton 33 and another two new peaks at d ¼ 1.9 and 1.6 ppm for -CH 2 protons 47,48 of the propane sultone group. This is to mention that these peaks are absent in pure PU and PU-GO polymer, which in turn, conrm the insertion of the sulfonate group in PU-GO polymer chains.…”

“…The SPU-GO polymer shows two broad peaks at 305 nm due to n / p* transition of urethane linkage and another one is at 372 nm assigned as n / p* transition due to the presence of the polar sulfonate group in polymer chains. 32,33 However, spectroscopic techniques clearly indicate the tagging of GO with the polyurethane chain and their subsequent sulphonation to convert into SPU-GO as ion conductive species. The molar masses of PP, PP-GO and PU-GO were determined by the gel permeation chromatography (GPC) measurements and are shown in Fig.…”

“…29,30 Polar functional groups in the main polymeric chain act as a medium to solvate the ionic species through intermolecular interactions and the ionic transport to occur by diffusion of the dissociated ions and their transport through the free volume of polymer matrix. 29,31 Polyurethane (PU) polymer matrix was functionalized to prepare polymer gel electrolytes, which were used to fabricated QDSSCs with co-sensitized CdS/CdSe photoanode to obtain 1.5% power conversion efficiency, 32 and Kumar et al 33 used the functionalized thermoplastic polyurethane gel electrolytes in QDSSCs with TiO 2 /CdS photoanode to achieve the PCE of 1.25%. Recently, PU-GO nanocomposites have attracted the attention of many researchers, especially, as the mechanical and electrical properties of nanocomposites were signicantly enhanced by adding only 1 wt% of GO during the polymerisation stage.…”