Fabrication of flexible all-inorganic nanocrystal solar cells by room-temperature processing

Loiudice, Anna; Rizzo, Aurora; Grancini, Giulia; Biasiucci, Mariano; Belviso, Maria R.; Corricelli, Michela; Curri, M. Lucia; Striccoli, Marinella; Agostiano, Angela; Cozzoli, P. Davide; Petrozza, Annamaria; Lanzani, Guglielmo; Gigli, Giuseppe

doi:10.1039/c3ee23928d

Cited by 31 publications

(47 citation statements)

References 49 publications

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“…1,4–8 The feasibility of PbS QDPV on flexible plastic substrates has been successfully demonstrated. 9 Device stability has also rapidly improved, with reports of >1000 h of operation stability 4,10 and >150 days of air stability. 8 …”

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confidence: 99%

Open-Circuit Voltage Deficit, Radiative Sub-Bandgap States, and Prospects in Quantum Dot Solar Cells

et al. 2015

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Quantum dot photovoltaics (QDPV) offer the potential for low-cost solar cells. To develop strategies for continued improvement in QDPVs, a better understanding of the factors that limit their performance is essential. Here, we study carrier recombination processes that limit the power conversion efficiency of PbS QDPVs. We demonstrate the presence of radiative sub-bandgap states and sub-bandgap state filling in operating devices by using photoluminescence (PL) and electroluminescence (EL) spectroscopy. These sub-bandgap states are most likely the origin of the high open-circuit-voltage (VOC) deficit and relatively limited carrier collection that have thus far been observed in QDPVs. Combining these results with our perspectives on recent progress in QDPV, we conclude that eliminating sub-bandgap states in PbS QD films has the potential to show a greater gain than may be attainable by optimization of interfaces between QDs and other materials. We suggest possible future directions that could guide the design of high-performance QDPVs.

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confidence: 99%

Open-Circuit Voltage Deficit, Radiative Sub-Bandgap States, and Prospects in Quantum Dot Solar Cells

et al. 2015

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“…Solution processed colloidal quantum dot (CQD) solar cells, mainly comprising lead sulphide (PbS), are one of the most promising class of low-cost, high-efficiency third generation solar cells thanks to their solution processability, bandgap tuning with quantum confinement and stability [1][2][3][4] . Recent developments in the field have reached over 11% power conversion efficiency (PCE) 5 .…”

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confidence: 99%

Breaking the Open-Circuit Voltage Deficit Floor in PbS Quantum Dot Solar Cells through Synergistic Ligand and Architecture Engineering

et al. 2017

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To realize the full potential of colloidal quantum dot (CQD) based solar cells, it is important to address the issue of large open circuit voltage (VOC) deficit which is a major roadblock in reaching higher efficiencies. The origin of the VOC deficit in these solar cells lies primarily in the presence of sub-bandgap trap states of the QDs. Here, we present a synergistic engineering framework to passivate these sub-bandgap states in PbS QDs through chemical surface passivation and remote passivation exploiting ligand and architecture engineering. In particular we form bulk nano-heterojunctions (BNH) by mixing PbS QDs with ZnO nanocrystals in conjunction with mixed ligand treatments to passivate surface traps. We employ the mixed ligand system of zinc iodide and 3-mercatopropyonic acid (MPA) to leverage the benefits of both organic and inorganic ligands for surface passivation and improved charge transport. This mixed ligand treatment in BNH architectures leads to record low Voc deficit for PbS QDs of 0.4 V -0.55 V compared to previously reported 0.6 -0.8 V for the range of 1.1 -1.35 eV bandgap PbS QDs. In summary, we have presented a methodology to reduce the VOC deficit PbS QD based solar cells. The mixed ligand treatment on the BNH reduces the VOC deficit as well as increases the current density compared to previously reported MPA treated BNH devices. Improved VOC, FF and JSC ultimately increases the device efficiency by 46% (5.2% to 7.6%). It should be noted that the bilayer devices that employ the mixed ligand treatment have thus far achieved higher PCE (of 9.9%) compared to the BNH reported herein, yet their Voc is lowered by 50 -60 mV compared to the BNH devices. This is due to the yet to be optimized charge transport along the ZnO percolation path in the BNH devices and our work points to the use of appropriate ligand treatments that have the potential to improve this further. The use of the ZnI2 in combination with MPA has resulted in a significant improvement in that aspect over the prior reports of MPA treated BNH devices and further progress can be expected by further optimization along this front. We have also presented a series of different characterizations to prove the role of BNH in trap passivation and hence lowering VOC deficit in case of PbS QD based solar cells.Although, this is a significant step towards producing high efficiency PbS solar cells with high VOC, the incorporation of ZnO inside the PbS QD matrix affects the optical absorption as well as the charge transport. Addressing these challenges can pave the way for high efficiency PbSQDs with even lower VOC deficit.

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“…The PbS QDs show a positive band peaking around 850 nm, ascribable to the PbS photobleaching (PB) due to the filling of the 1S state, and a negative signal at shorter wavelengths, peaking around 550 nm, arising from photoinduced absorption (PA) from populations of QD surface trap states. 26 The PA band of the PbS QDs deposited on TiO 2 NRs presents a higher intensity, while the PB band of the two systems is comparable. This suggests that, upon photoexcitation, a higher density of trap states is populated in the PbS QDs deposited on TiO 2 NRs, relative to QDs deposited on the BNCs, to the detriment of the percentage of the electrons injected into the TiO 2 .…”

Section: ■ Results and Discussionmentioning

confidence: 96%

Three-Dimensional Self-Assembly of Networked Branched TiO₂ Nanocrystal Scaffolds for Efficient Room-Temperature Processed Depleted Bulk Heterojunction Solar Cells

Loiudice

Grancini

Taurino

et al. 2014

ACS Appl. Mater. Interfaces

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In this work, we report on ∼4% power conversion efficiency (PCE) depleted bulk heterojunction (DBH) solar cells based on a high-quality electrode with a three-dimensional nanoscale architecture purposely designed so as to maximize light absorption and charge collection. The newly conceived architecture comprises a mesoporous electron-collecting film made of networked anisotropic metal-oxide nanostructures, which accommodates visible-to-infrared light harvesting quantum dots within the recessed regions of its volume. The three-dimensional electrodes were self-assembled by spin-coating a solution of colloidal branched anatase TiO2 NCs (BNC), followed by photocatalytic removal of the native organic capping from their surface by a mild UV-light treatment and filling with small PbS NCs via infiltration. The PCE ∼ 4% of our TiO2 BNC/PbS QD DBH solar cell features an enhancement of 84% over the performance obtained for a planar device fabricated under the same conditions. Overall, the DBH device fabrication procedure is entirely carried out under mild processing conditions at room temperature, thus holding promise for low-cost and large-scale manufacturing.

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Fabrication of flexible all-inorganic nanocrystal solar cells by room-temperature processing

Cited by 31 publications

References 49 publications

Open-Circuit Voltage Deficit, Radiative Sub-Bandgap States, and Prospects in Quantum Dot Solar Cells

Open-Circuit Voltage Deficit, Radiative Sub-Bandgap States, and Prospects in Quantum Dot Solar Cells

Breaking the Open-Circuit Voltage Deficit Floor in PbS Quantum Dot Solar Cells through Synergistic Ligand and Architecture Engineering

Three-Dimensional Self-Assembly of Networked Branched TiO₂ Nanocrystal Scaffolds for Efficient Room-Temperature Processed Depleted Bulk Heterojunction Solar Cells

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Fabrication of flexible all-inorganic nanocrystal solar cells by room-temperature processing

Cited by 31 publications

References 49 publications

Open-Circuit Voltage Deficit, Radiative Sub-Bandgap States, and Prospects in Quantum Dot Solar Cells

Open-Circuit Voltage Deficit, Radiative Sub-Bandgap States, and Prospects in Quantum Dot Solar Cells

Breaking the Open-Circuit Voltage Deficit Floor in PbS Quantum Dot Solar Cells through Synergistic Ligand and Architecture Engineering

Three-Dimensional Self-Assembly of Networked Branched TiO2 Nanocrystal Scaffolds for Efficient Room-Temperature Processed Depleted Bulk Heterojunction Solar Cells

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Three-Dimensional Self-Assembly of Networked Branched TiO₂ Nanocrystal Scaffolds for Efficient Room-Temperature Processed Depleted Bulk Heterojunction Solar Cells