Current Challenges in the Development of Quantum Dot Sensitized Solar Cells

Abstract

Quantum dot sensitized solar cells (QDSSCs) have experienced a continuous performance growth in the past years presenting a photoconversion efficiency >13%. QDSSCs constitute a smart approach to take advantage of the properties of semiconductor quantum dots (QDs), mitigating the transport constrains. In contrast with other QD solar cell configurations, for QDSSCs, the record efficiencies have been reported with Pb and Cd‐free based sensitizers. The development of techniques in order to provide photoanodes with very high QD loading and the discovery of new electrolytes, including all solid configurations, are the most important future challenges that this technology must address to further increase cell performance and stability.

Improving the Efficiency of Quantum Dot Sensitized Solar Cells beyond 15% via Secondary Deposition

“…The distinguished optoelectronic properties of quantum dot (QD) light absorbers, such as high stability toward light, heat, and moisture, high extinction coefficient, multiple exciton generation (MEG) possibility, solution processability, etc., make QD-sensitized solar cells (QDSCs) a promising low-cost third-generation photovoltaic cell with a theoretical power conversion efficiency (PCE) of up to 44%. − Benefiting from the exploitation of near-infrared absorption QD sensitizers and the high-efficiency photogenerated electron extraction, − the development of high-performance counter electrodes, especially Ti-mesh-supported mesoporous carbon counter electrodes (MC/Ti CE), − as well as an interface engineering strategy using an energetic barrier layer to suppress undesired charge recombinations, − the certified PCE record of QDSCs has been improved from less than 5% to over 14% in the past decade. , However, this value is still far less than the corresponding theoretical value (44%), as well as those for other emerging solar cells. , One of the main reasons for the intermediate photovoltaic performance of QDSCs is due to the low QD loading (i.e., low QD coverage) on the photoanode surface and the concomitant insufficient light-harvesting capacity as well as charge recombination loss in the cell device. ,− A high QD loading on photoanode surface is a prerequisite for high photocurrent and high photovoltaic performance in QDSCs. − This is because high QD loading can reduce the necessary thickness of a sensitized photoanode to capture all incident solar photons. A thin photoanode means a short transportation path for photogenerated electrons through the photoanode to the current collector plate and consequently a reduced possibility for undesirable charge recombination. − Furthermore, a high QD loading corresponds to a decrease in the proportion of the uncovered TiO 2 surface directly exposed to the electrolyte and less possibility of photogenerated electrons captured by the redox couple in the electrolyte, thereby benefiting the photovoltaic performance, the especially photovoltage and fill factor, of a cell device. − …”

Conjugation of gold nanoparticles with multidentate surfactants for enhanced stability and biological properties

“…We hope this work will have a significant impact on nanoparticle assisted drug delivery and bioimaging. 17,56,57 This result can be generalized to nanoparticle functionalization in different fields of materials science and technology well beyond nanobiotechnology, ranging from nanoparticle sensitized solar cells 58,59 to sensing, 60 catalysis, 61 and others. 62…”

Electron Transfer at Quantum Dot–Metal Oxide Interfaces for Solar Energy Conversion

“…On top of the losses that we have mentioned, devices based on QD–MO interfaces such as QD sensitized solar cells suffer in practice from other extrinsic loss mechanisms; including recombination induced by traps, transmission losses due to poor QD loading, and photostability issues linked with the employed constituents. ,,− In any case, to date, the best performing QD sensitized solar cell reveals a remarkable certified efficiency of 15.2% . It is worth commenting here that QD sensitized cells are often classified within the general umbrella of “QD solar cells”, where cells employing bulklike QD superlattices hold the record efficiency. , We believe this is misleading, as sensitized solar cells employing a dye or a QD as a chromophore operate as excitonic solar cells, , while cells employing QD superlattices operate as bulk-like devices relying on the generation of free delocalized charge carriers upon photon absorption. ,− While record performing QD sensitized solar cells have reduced efficiencies when compared with those based on QD superlattices, they currently outperform in efficiency their counterpart built around molecular sensitizers (currently delivering cells with about 12% efficiency). , …”