Nikhil Chander

Reduced ultraviolet light induced degradation and enhanced light harvesting using YVO4:Eu3+ down-shifting nano-phosphor layer in organometal halide perovskite solar cells

We report a simple method to mitigate ultra-violet (UV) degradation in TiO2 based perovskite solar cells (PSC) using a transparent luminescent down-shifting (DS) YVO4:Eu3+ nano-phosphor layer. The PSC coated with DS phosphor showed an improvement in stability under prolonged illumination retaining more than 50% of its initial efficiency, whereas PSC without the phosphor layer degraded to ∼35% of its initial value. The phosphor layer also provided ∼8.5% enhancement in photocurrent due to DS of incident UV photons into additional red photons. YVO4:Eu3+ layer thus served a bi-functional role in PSC by reducing photo-degradation as well as enhancing energy conversion efficiency.

Spray deposited copper zinc tin sulphide (Cu2ZnSnS4) film as a counter electrode in dye sensitized solar cells.

Stoichiometric thin films of Cu2ZnSnS4 (CZTS) were deposited by the spray technique on a FTO coated glass substrate, with post-annealing in a H2S environment to improve the film properties. CZTS films were used as a counter electrode (CE) in Dye-Sensitized Solar Cells (DSCs) with N719 dye and an iodine electrolyte. The DSC of 0.25 cm(2) area using a CE of CZTS film annealed in a H2S environment under AM 1.5G illumination (100 mW cm(-2)) exhibited a short circuit current density (JSC) = 18.63 mA cm(-2), an open circuit voltage (VOC) = 0.65 V and a fill factor (FF) = 0.53, resulting in an overall power conversion efficiency (PCE) = 6.4%. While the DSC using as deposited CZTS film as a CE showed the PCE = 3.7% with JSC = 13.38 mA cm(-2), VOC = 0.57 V and FF = 0.48. Thus, the spray deposited CZTS films can play an important role as a CE in the large area DSC fabrication.

Influence of surface plasmon resonances of silver nanoparticles on optical and electrical properties of textured silicon solar cell

Here, we report average reflectance reduction of ∼8% in wavelength range of 300–1100 nm after coupling surface plasmon resonances (SPRs) of silver nanoparticles (NPs) to textured silicon (T-Si) surface. The enhancement of photocurrent from T-Si solar cell in off-resonant SPR region observed due to better radiative efficiency of NPs leading to outflow of scattered far-field into silicon maximized power generating electrons. Improvement in series resistance, fill factor, and open-circuit voltage (insensitive NPs size and morphology) are also observed with NPs along with photocurrent enhancement (sensitive to NPs sizes), which resulted cell efficiency enhancement from 4.49% to 6.42% for large area of 12.24 cm2.

Improved stability and enhanced efficiency of dye sensitized solar cells by using europium doped yttrium vanadate down-shifting nanophosphor

Through detailed experiments, it has been deduced that ultraviolet (UV) light is a major factor in the degradation of dye-sensitized solar cell (DSSC) performance due to generation of surface defects in nanoporous TiO2 and dye structural modification with free radical formation. We describe a simple spray deposition method to coat europium doped yttrium vanadate (YVO4:Eu3+) down-shifting (DS) phosphor nanoparticles (NPs) on the front side of DSSCs in order to enhance photocurrent and mitigate UV induced degradation. The nanophosphor provides an enhancement in short-wavelength spectral response of solar cells, and long-term stability is also improved under illumination, due to down-shifting of high energy UV photons to the visible region. Our observations demonstrate that the DS nanophosphor layer can be used as an optical filter with visible light transmission and UV light absorption, through placement on the front surface of DSSCs to provide stability, as well as for improving the performance.

Improving the Short-Wavelength Spectral Response of Silicon Solar Cells by Spray Deposition of YVO 4 :Eu 3+ Downshifting Phosphor Nanoparticles

Europium-doped yttrium vanadate downshifting phosphor nanoparticles (NPs) have been coated on top of monocrystalline silicon solar cells, having efficiency more than 15%, by a spray deposition technique. The effects of phosphor NPs on solar cells with antireflection coating (ARC) have been studied. The optimized quantity of phosphor NPs provides a photocurrent enhancement of ~2.1% for monosilicon solar cells. External quantum efficiency data of high-efficiency ARC layer-coated silicon solar cells conclusively show that the enhancement in short-wavelength spectral response is mainly due to downshifting effects of the phosphor NPs. A small increment in a long-wavelength spectral response is also observed due to the scattering effects of phosphor NPs, which also results in a small enhancement of effective diffusion length of minority carriers in the base region.

Nanocrystalline titanium dioxide sensitised with natural dyes for eco-friendly solar cell application

Indigenously available natural dyes have been used as natural sensitisers for dye-sensitised solar cells (DSSCs) in this study. The chlorophyll extract from Azadirachta indica (Neem) leaves and anthocyanin extract from poinsettia bracts were obtained using ethanol. Nanoparticles of TiO2 having an average size of 80 nm were deposited on fluorine-doped tin oxide (FTO) coated glass using the electrophoretic deposition method. Counter electrode was prepared by spraying conductive graphite over FTO glass substrates. A sandwich-type cell was assembled, and the fill factor and the power conversion efficiency were measured under a light source simulating AM 1.5 with an intensity of 100 mW/cm2. DSSCs containing chlorophyll and anthocyanin exhibited open circuit voltages of 404 and 406 mV with fill factors of 40.1% and 45.8%, respectively. The mixture of the two natural dyes as sensitiser for DSSCs gave the best photovoltaic conversion efficiency of approximately 1%.