Papers by Keyword: Hybrid Solar Cells

Abstract: Recently, hybrid solar cell that consists of a combination of organic and inorganic materials offers promise in increasing efficiency. Combination of conjugated polymer of Poly (3-hexyl thiophene)/P3HT which has the highest hole mobility with inorganic materials which has high electron mobility, good physical and chemical stability of inorganic nanocrystals, shows a better performance of hybrid solar cells. We have conducted a measurement to investigate the charge carrier transport in active material of hybrid solar cells by using muon spin relaxation (μSR) with light irradiation. A bulk sample used in this study is hybrid organic-inorganic material consisting of regio-regular P3HT and ZnO nanoparticles. Longitudinal-field μSR measurements were performed in magnetic field ranging from 0 to 395 mT at temperature of 10 K, 15 K and 25 K. Based on μSR measurement with light irradiation, we found that for those temperatures, longitudinal field dependence of λ₁ was proportional with C-H^0.5 curve indicating three-dimensional inter-chain diffusion. We assume that light irradiation initiates the production of exciton that increases the number of charge carrier in the sample and transports not only along the chain of polymer (one-dimensional) but also perpendicular to other chain of polymer (three-dimensional). With light irradiation, the crossover temperature from one-dimensional to three-dimensional of regio-regular P3HT and ZnO nanoparticles bulk sample was obtained at lower temperature of 10 K compared to previous result at 25 K without light irradiation.

Abstract: In this work, the development of solution-processed bulk heterojunction hybrid solar cells based on CdSe quantum dot (QD) and conjugated polymer poly [2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b] dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)], PCPDTBT was performed. The photoactive layer was formed by integrating CdSe QDs onto multiwalled carbon nanotubes (CNTs). A simple method of thiol functionalization in the interface CNTs and CdSe QDs has been investigated. Integration of CNTs enhances long-term performance of solar cells devices. Initial PCE values of about 1.9 % under AM1.5G illumination have been achieved for this hybrid CNT-CdSe photovoltaic device. In addition, the long-term stability of the photovoltaic performance of the devices was investigated and found superior to CdSe QD only based devices. About 84 % of the initial PCE remained after storage in a glove box for one year without any further encapsulation. It is concluded that the improvement is mainly due to a strong binding between thiol functionalized CNTs and CdSe QDs, resulting preservation of the nanomorphology of the hybrid film over time.

Abstract: In this work, the development of room-temperature solution-processed hybrid solar cells based on carbon nanotubes (CNT) - CdSe quantum dot (QD) hybrid material incorporated into a layer of conjugated polymer poly [2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b′] dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)], PCPDTBT, has been demonstrated. Incorporation of multi walled CNTs helps to improve the long-term efficiency of the solar cells in respect of power conversion efficiency (PCE) and short-circuit current density (Jsc) compared to QD only based devices. For the formation of the hybrid material hexadecylamine (HDA)/ trioctylphosphine oxide (TOPO) capped CdSe QDs were attached to CNTs by engineering the interface between CNTs and CdSe QDs by introducing thiol functional groups to CNTs. Initial PCE values of about 1.9 % under AM1.5G illumination have been achieved for this hybrid CNT-CdSe photovoltaic device. Furthermore, the long term stability of the photovoltaic performance of the devices was investigated and found superior to CdSe QD only based devices. About 90 % of the original PCE remained after storage in a glove box for almost one year without any further encapsulation. It is assumed that the improvement is mainly due to the thiol-functionalization of the CNT interface leading to a strong binding of CdSe QDs and a resulting preservation of the nanomorphology of the hybrid film over time.

Abstract: Nanocomposites containing inorganic semiconductor nanomaterials are of tremendous interest for low-cost 3^rd generation solar cells. A variety of possible materials and structures could be potentially used to reduce processing costs which is highly attractive for large scale production of solar cells. Controlling the morphology and surface chemistry of nanomaterials remains a key challenge that has major knock-on effects in devices. Herein, an attempt is made to highlight some of the challenges and the possible solutions for depositing high quality thin film composites for solar cell devices.

Abstract: Different nanocomposite materials consisting of semiconducting CdSe nanocrystals (NCs) and a low band gap copolymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b:3.4-b’]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) were prepared, morphologically characterized, and tested in hybrid solar cells. In addition, a PCPDTBT-based rod-coil diblock copolymer was synthesized through a grafting-onto approach and a preliminary evaluation of the morphology of the hybrid nanocomposites with CdSe NCs was performed.

Abstract: The optical characterization of Molybdenum diselenide (MoSe₂) and polyaniline (PANI) has been carried in the wavelength range 200 nm to 2500 nm. The detailed analysis of the optical properties has been carried out only for a range 200 nm to 800 nm from which the indirect band gap around 1.42 eV for MoSe₂ and 1 eV and 2.5 eV for PANI was evaluated. It was interesting to note that π π* transitions lead to two distinct orders of energy gaps. The hybrid cells were fabricated using a photosensitive interface between MoSe₂ and PANI. Various parameters of these heterostructure hybrid cells have been evaluated and it was found that the photoconversion efficiency was around 1%. Using the solar cell characteristics, the presence of trapping centers at the n-MoSe₂/ p-PANI interface has been confirmed.

Abstract: In recent years, semiconductor nanomaterials have been extensively studied and reports are available for their preparation methods, physical and chemical properties of nanoparticles and their characterization techniques. Because of their potential applications, ZnS nanoparticles are recently major area of research. It is an important inorganic material for a variety of applications including photoconductors, solar cells, field effect transistors, sensors, transducers optical coatings and light-emitting materials. Inorganic nano-particles have found potential application in various electronic devices. Synthesis, shape and size control are important issues for nano-particles research. Various nano-structured materials have found potential applications in optical and electrical devices such as photoconductors, LEDs, solar cells, field effect transistors, optical coatings etc. ZnS has wide band gap ranging from 3.5 to 3.8 eV at room temperature and the band gap can be tuned in the UV region by controlling the size of the nano-particles. In the present work we have studied the synthesis of ZnS nano-particles, their characterization to investigate various properties such as size, structure, band gap and luminescence via different characterization tools. The particles were then used as acceptors for fabrication of organic hybrid solar cells.

Abstract: Hybrid solar cells based on conjugated polymer poly(2-methoxy,5-(2’-ethylhexyloxy)-p-phenylene vinylene (MEH-PPV) and inorganic n-type zinc oxide (ZnO) nanoparticles were investigated. Polymer solar cells consisting of conducting polymer alone have low minority carrier mobility, for example, MEH-PPV has a high hole mobility but a low electron mobility. The intrinsic carrier mobility imbalance in the MEH-PPV severely limits the performance of pure polymer based solar cells. To overcome this imbalance, another material, i.e. n-type ZnO particles, is incorporated to act as an electron acceptor and a pathway for electron transport. In this experiment, as an active layer, ZnO nanoparticles synthesized in-house were blended with MEH-PPV purchased from Sigma-Aldrich. The front transparent conduction oxide (TCO) electrode used was commercial glass substrate coated with indium tin oxide (ITO) thin film. Blends of MEH-PPV with 0-30 wt% of ZnO in 1,2-dichlorobenzene were prepared and fabricated as active layers of the solar cells. The PEDOT:PSS and active layer were spin-coated onto ITO coated glass substrate. Aluminum was used for the top electrodes. The effects of ZnO solid content and film morphology on the performance of MEH-PPV:ZnO nanoparticle composite solar cells were investigated. Transmission electron microscopy (TEM) revealed that the ZnO nanoparticles consisted of a mixture of spherical and rod-like shapes. An increase in ZnO solid content resulted in an increase in size of the ZnO network. This was found to increase electron transport and, hence, improve solar cell performance.