Thin film solar cells based on the heterojunction of colloidal PbS quantum dots with CdS (original) (raw)
Related papers
Advanced Functional Materials, 2017
CdS thin films are a promising electron transport layer in PbS colloidal quantum dot (CQD) photovoltaic devices. Some traditional deposition techniques, such as chemical bath deposition and RF (radio frequency) magnetron sputtering, have been employed to fabricate CdS films and CdS/ PbS CQD heterojunction photovoltaic devices. However, their power conversion efficiencies (PCEs) are moderate compared with ZnO/PbS and TiO 2 / PbS heterojunction CQD solar cells. Here, efficiencies have been improved substantially by employing solution-processed CdS thin films from a singlesource precursor. The CdS film is deposited by a straightforward spin-coating and annealing process, which is a simple, low-cost, and high-material-usage fabrication process compared to chemical bath deposition and RF magnetron sputtering. The best CdS/PbS CQD heterojunction solar cell is fabricated using an optimized deposition and air-annealing process achieved over 8% PCE, demonstrating the great potential of CdS thin films fabricated by the single-source precursor for PbS CQDs solar cells.
Enhanced Open-Circuit Voltage of PbS Nanocrystal Quantum Dot Solar Cells
Scientific Reports, 2013
Nanocrystal quantum dots (QD) show great promise toward improving solar cell efficiencies through the use of quantum confinement to tune absorbance across the solar spectrum and enable multi-exciton generation. Despite this remarkable potential for high photocurrent generation, the achievable open-circuit voltage (V oc ) is fundamentally limited due to non-radiative recombination processes in QD solar cells. Here we report the highest open-circuit voltages to date for colloidal QD based solar cells under one sun illumination. This V oc of 692 6 7 mV for 1.4 eV PbS QDs is a result of improved passivation of the defective QD surface, demonstrating V o c mV ð Þ~553E g q-59 as a function of the QD bandgap (E g ). Comparing experimental V oc variation with the theoretical upper-limit obtained from one diode modeling of the cells with different E g , these results clearly demonstrate that there is a tremendous opportunity for improvement of V oc to values greater than 1 V by using smaller QDs in QD solar cells.
PbS QUANTUM DOT-BASED HETROJUNCTION SOLAR CELLS
2014
This study investigates the influence of nanoparticles (NPs) size on their optical properties, and the effect of combination of lead sulfide (PbS) quantum dots (QDs), with n-type and p-type NPs, on the photogenerated charge carriers transport across the heterojunction solar cell structure. PbS QDs, of a range of sizes, were synthesized using a co-precipitation process. In this study, p-type NPs, which are poly [3,4-ethylenedioxythiophene] –poly [styrenesulfonate] (PEDOT: PSS), copper oxide (CuO) and graphene oxide (GO); and n-type NPs which are zinc oxide (ZnO), titanium dioxide (TiO2), cadmium sulfide (CdS) and bismuth sulfide (Bi2S3), were synthesized and characterized by SEM and UV-visible spectrophotometers. The NPs with enhanced optical properties were utilized in heterojunction solar cell structures via spin coating, chemical bath deposition and SILAR cycle methods. The morphology and the theoretical band energy diagram for each cell were examined. The photovoltaic performance...
Recent Developments of Solar Cells from PbS Colloidal Quantum Dots
Applied Sciences
PbS (lead sulfide) colloidal quantum dots consist of crystallites with diameters in the nanometer range with organic molecules on their surfaces, partly with additional metal complexes as ligands. These surface molecules are responsible for solubility and prevent aggregation, but the interface between semiconductor quantum dots and ligands also influences the electronic structure. PbS quantum dots are especially interesting for optoelectronic applications and spectroscopic techniques, including photoluminescence, photodiodes and solar cells. Here we concentrate on the latter, giving an overview of the optical properties of solar cells prepared with PbS colloidal quantum dots, produced by different methods and combined with diverse other materials, to reach high efficiencies and fill factors.
Bandgap engineering for enhancing photovoltaic properties of PbS quantum dot solar cells
The Japan Society of Applied Physics, 2016
°(D1) Chao Ding, 1Yaohong Zhang, 1 Shuzi Hayase, 2,3 Yuhei Ogomi,3 Taro Toyoda,1,3 and Qing Shen 1,3 Univ. Electro-Commun.1, Kyushu Inst. Tech.2, CREST JST3 Email: shen@pc.uec.ac.jp Introduction Colloidal quantum dots solar cells (CQDSCs) have recently reached promising power conversion efficiencies (η) of over 10%.1 However, CQD solids have relatively short minority carrier diffusion length (≤100nm), which limited the further improvement in the photovoltaic performance of CQDPV devices. Colloidal quantum dots offer broad tuning of semiconductor band-structure via the quantum size effect. Using a spatial energy band gradient engineering with quantum dots (QDs) of different sizes to enhance the minority carrier diffusion length of a photovoltaic device is a promising strategy for increasing the solar cell efficiency. In this study, we developed an air condition solution-processed TiO2/PbS quantum dot heterojunction solar cells, by applying a band alignment method to the active layer ...
Highly Monodispersed PbS Quantum Dots for Outstanding Cascaded-Junction Solar Cells
High-performance cascaded-junction quantum dot solar cells (CJQDSCs) are fabricated from as-prepared highly monodispersed lead sulfide QDs. The cells have a high power conversion of 9.05% and a short-circuit current density of 32.51 mA cm −2. A reliable and effective stratagem for fabricating high-quality lead sulfide quantum dots (QD) is explored through a " monomer " concentration-controlled experiment. Robust QDSC performances with different band gaps are demonstrated from the as-proposed synthesis and processing stratagems. Various potential CJQDSCs can be envisioned from the band edge evolution of the QDs as a function of size and ligands reported here. Q uantum dots (QDs) are well-known as infinitesimal semiconducting nanocrystals with a physical size in the range of their Bohr radius. 1 Because of their discrete density of state, the band gap (ε gap) of QDs can be compatibly modified by manipulating their dimensions, which leads to extensive studies for optoelectronics applications. 2 In particular, facile solution processability and ε gap customizability to the solar spectrum makes QDs one of the most promising materials for future emerging solar cells. 3 Prevalent studies in QD solar cells (QDSCs), mainly concern lead sulfide (PbS) materials because of their large Bohr radius (20 nm) and wide band gap (ε gap) tuning range (0.4−1.5 eV). 4 Profiting from improved process technologies, i.e. better passivation and optimized p−n junction structure, remarkable power conversion efficiencies (PCEs) of ca. 10% have been achieved recently. 5,6 However, in spite of the demonstrated abilities and fascinating features in the QDSCs, there are still challenges which need to be addressed in terms of material quality control and device architecture design. 3 For instance, a vast number of works have been performed to synthesize high-quality PbS QDs, 7,8 but it is still a challenge to reproduce identical QDs from different batches, which hampers stable device performance. As one of the most promising QD device architectures, solar cells made from cascading various sizes of QDs have been proposed and tentatively studied. 9−13 However, because of poor size control of the QDs, to date, none of the works report good PCE performance. In this work, we elucidate an effective and reliable PbS QD synthesis protocol for fabricating high-performance and robust QDSCs. Through the systematic adjustment of the precursor concentration, in a fixed reaction temperature and quench time, a wide range of different sizes of colloidal PbS QDs is produced with a narrow size distribution and high reproducibility. The effects of quantum confinement and surface functionalization for different ligands and QD size is subject to a rationalization analysis. Finally, based on the understanding gained of the optical−electrical properties of as-prepared PbS QDs, three distinct sizes of PbS QDs are selected and fabricated into cascaded-junction solar cells (CJSC) under ambient air conditions. The device structure is illustrated in Figure 1a, which employs layers of different sizes of QDs treated with different ligands for tuning their relative band alignment and also photon energy absorption. The elaborately designed devices show impressively high PCE and short-circuit current density compared with those of previously reported devices. 5,6 The assembling of CJSC requires highly monodispersed PbS QDs with a range of different possible sizes, ensuring small coplanar charge transport barriers and distinct size-dependent optical properties. 2 QDs utilized in the light absorber layers
PbS/CdS Core/Shell Nanocrystals For Solution-Processed Colloidal Quantum Dot Solar Cells
MRS Proceedings, 2014
ABSTRACTAn epitaxial shell of cadmium sulphide is grown on lead sulphide quantum dots in order to reduce the concentration of surface defects. Thin solid films of these core/shell materials are found to have low carrier concentrations due to effective surface passivation which reduces the number of dangling bonds. In this paper PbS/CdS is used as a quasi-intrinsic layer in p-i-n photovoltaic devices where PbS acts as the p-layer and ZnO the n-layer. By studying different permutations of these layers and the degree of PbS p-type doping by annealing we optimise fill factor and open-circuit voltage.
Performance of PbSe quantum dot based heterojunction solar cells: Dependence on ligand type
The Japan Society of Applied Physics, 2016
Univ. Electro-Commun., Kyushu Inst. Tech., Nanjing Tech. Univ., CREST JST Yaohong Zhang, Chao Ding, Shuzi Hayase,Yuhei Ogomi, Jin Chang, Taro Toyoda, Qing Shen, Email: shen@pc.uec.ac.jp Introduction Quantum dots (QDs) based solar cells have attracted more and more interests as a promising candidate for the next generation solar cells. Compared with conventional solar cells, QDs solar cells (QDSCs) are easier to prepare with low fabrication cost. Additionally, QDs present high extinction coefficients, tunable absorption spectra, and multiple exciton generation (MEG) effect. PbSe QDs have attracted attention due to their small bulk bandgap, high dielectric constant, and large exciton Bohr radius. However, the performance of PbSe based QDSCs tend to quickly degrade after the solar cells expose to air. Here, we found a modified method to synthesis air stable PbSe QDs and investigate the effect of ligand on the performance of PbSe QDSCs. Experimental Method Colloidal PbSe QDs were synthe...
Efficient, Stable, and Low-Cost PbS Quantum Dot Solar Cells with Cr–Ag Electrodes
Nanomaterials
PbS quantum dots (QDs) are a promising nanostructured material for solar cells. However, limited works have been done to explore the active layer thickness, layer deposition techniques, stability improvement, and cost reduction for PbS QD solar cells. We address those issues of device fabrication herein and suggest their possible solutions. In our work, to get the maximum current density from a PbS QD solar cell, we estimated the optimized active layer thickness using Matlab simulation. After that, we fabricated a high-performance and low-cost QD photovoltaic (PV) device with the simulated optimized active layer thickness. We implemented this low-cost device using a 10 mg/mL PbS concentration. Here, spin coating and drop-cast layer deposition methods were used and compared. We found that the device prepared by the spin coating method was more efficient than that by the drop cast method. The spin-coated PbS QD solar cell provided 6.5% power conversion efficiency (PCE) for the AM1.5 l...
Quantum dot PbS 0.9 Se 0.1 /TiO 2 heterojunction solar cells
Nanotechnology, 2012
We report on photovoltaic cells based on ternary PbS(0.9)Se(0.1) quantum dots utilizing a heterojunction type device configuration. The best device shows an AM 1.5 power conversion efficiency of 4.25%. Furthermore, this ternary PbS(x)Se(1-x) quantum dot heterojunction device has a peak external quantum efficiency above 100% at 2.76 eV, approximately 2.7× the bandgap energy. The ternary quantum dots combine the higher short circuit currents of the binary PbSe system with the higher open circuit voltages of the binary PbS system.