Effect of Organic and Inorganic Passivation in Quantum-Dot-Sensitized Solar Cells

Abstract

The effect of semiconductor passivation on quantum-dot-sensitized solar cells (QDSCs) has been systematically characterized for CdS and CdS/ZnS. We have found that passivation strongly depends on the passivation agent, obtaining an enhancement of the solar cell efficiency for compounds containing amine and thiol groups and, in contrast, a decrease in performance for passivating agents with acid groups. Passivation can induce a change in the position of TiO 2 conduction band and also in the recombination rate and nature, reflected in a change in the β parameter. Especially interesting is the finding that β, and consequently the fill factor can be increased with the passivation treatment. Applying this strategy, record cells of 4.65% efficiency for PbS-based QDSCs have been produced. SECTION: Energy Conversion and Storage; Energy and Charge Transport I n the past few years, the interest in the use of light-absorbing inorganic semiconductor materials for nanostructured photovoltaic devices has increased enormously, in particular, in the case of semiconductor quantum dots (QDs), when the semiconductor particle size is smaller than its Bohr radius and quantum confinement regime is attained. 1−7 These materials are extremely interesting for the development of photovoltaic applications for several reasons: tunable band gap, high extinction coefficient, large intrinsic dipole moment, and easy and cheap production.

Effect of the electrophoretic deposition of Au NPs in the performance CdS QDs sensitized solar Cells

“…Analyzing the curves, it can be seen than the TiO 2 /CdS films (black line), have a J sc of 9.85 mA/cm 2 an V oc of 575 mV, a FF of 46.5% and a photoconversion efficiency of 2.63%, which is in good agreement with the efficiencies reported for this kind of solar cells [13,14,16,18,[46][47][48][49]. When a 30s Au NPs deposit is applied (TiO 2 /Au(0.5)/CdS), a small reduction in the photocurrent is obtained (J sc 9.5 mA) maintaining relatively constant for longer deposition times (9.5 and 9.4 mA for 2.5 and 7.5 min respectively).…”

Efficient passivated phthalocyanine-quantum dot solar cells

“…This fact together with the absence of EQE at the light absorption region of the dye suggest that the main effect of the interaction is the passivation of the QD surface. 22 As it has been commented previously, surface states in QDs can act as recombination centers of photoexcited electron-hole pairs, before electron injection into electrode. Passivation of these states increases device IPCE and photocurrent.…”

“…21 In this sense, efficient passivation of QD surface state is an strategy commonly employed to enhance QDSCs performance. 19,21,22 Phthalocyanines (Pcs) are aromatic macroheterocycles which have been used successfully in DSSCs because they absorb intensely in the red spectral region, are able to inject into titanium oxide and are thermal and photochemicallyverystable compounds. 23 Theirtendency to form aggregates on the TiO 2 surface, which reduces the efficiency of solar cells, can be countered with the introduction ofbulky groups in the peripheral 24 or apical 25 positions going to efficiencies up to 6.5%.…”

ZnS/SiO2 Passivation Layer for High-Performance of TiO2/CuInS2 Quantum Dot Sensitized Solar Cells

“…Interestingly, the combination of ZnS coating with different dipolar molecules absorbed on the TiO2 surface has been demonstrated to improve the performance of QDSSCs [18].…”