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Solid-state-ligand-exchange free quantum dot ink-based solar cells with an efficiency of 10.9%
Aqoma, Havid,Jang, Sung-Yeon The Royal Society of Chemistry 2018 Energy & environmental science Vol.11 No.6
<P>While colloidal quantum dot based solar cells (CQDSCs) have recently achieved power conversion efficiencies (PCE) up to 11.3%, the CQD active layers are fabricated almost exclusively by a combined process of <I>in situ</I> solid-state ligand exchange (SSE) with multiple layer-by-layer (LbL) deposition, which has been a major obstacle to high-throughput processing. In this work, we developed, for the first time, high-efficiency CQDSCs without using either the SSE or LbL technique. The fabrication of n-p quantum dot junctions by SSE-free direct coating was achieved using n-type CQD ink and p-type CQD ink. The ink based devices achieved a PCE of ∼11%, which is comparable to the current state-of-the-art performance. The CQD inks enabled, for the first time, use of the doctor-blade coating method for device fabrication. Notably, the PCE of the bladed CQDSCs was remarkably high, at @@>@@10%, which suggests its potential use in other industrially friendly processes.</P>
Dasom Park,Aqoma, Havid,Ilhwan Ryu,Sanggyu Yim,Sung-Yeon Jang IEEE 2016 IEEE journal of selected topics in quantum electro Vol.22 No.1
<P>Colloidal quantum-dot-based photovoltaic devices (CQDPVs) were fabricated at room temperature in air atmosphere via a spraying technique. Lead sulfide colloidal quantum dots (CQDs) were utilized for this process and various fabrication conditions such as the spraying pressure, types of ligand molecules, duration of ligand exchange, and the band-gap of the CQDs were investigated in order to optimize the device performance. The power conversion efficiency reached 4.00% (V-OC of 0.57V, J(SC) of 11.79 mA center dot cm(-2), and FF of 0.60) when similar to 145 nm thick sprayed CQD layers were utilized; this value is comparable to that achieved with the conventional spin-coated devices. The generality of the conditions used for fabrication of the sprayed CQDPVs was demonstrated in the fabrication of various CQDs having different band-gaps (1.34-1.61 eV). This technique provides an avenue for the application of a high-throughput process for CQDPV fabrication. Because the materials used herein for device fabrication are not completely optimized, there is further scope for improving device performance.</P>
Highly efficient air-stable colloidal quantum dot solar cells by improved surface trap passivation
Azmi, Randi,Sinaga, Septy,Aqoma, Havid,Seo, Gabsoek,Ahn, Tae Kyu,Park, Minsuk,Ju, Sang-Yong,Lee, Jin-Won,Kim, Tae-Wook,Oh, Seung-Hwan,Jang, Sung-Yeon unknown 2017 Nano energy Vol.39 No.-
<P><B>Abstract</B></P> <P>While the power conversion efficiency (PCE) of colloidal quantum dot (CQD) solar cells can reach > 10%, the major obstacle for charge extraction and energy loss in such devices is the presence of surface trap sites within CQDs. In this work, highly trap-passivated PbS CQDs were developed using a novel iodide based ligand, 1-propyl-2,3-dimethylimidazolium iodide (PDMII). We examined the effects of PDMII on the surface quality of PbS-CQDs and compared them with TBAI, which is the best-selling iodide based ligand. By using PDMII, improved surface passivation with reduced sub-bandgap trap-states compared to TBAI was achieved. The reduced trap density resulted in enhanced charge extraction with diminished energy loss (0.447eV) in the devices. Solar cell devices using our PDMII based CQDs displayed high PCE and air stability. The certified PCE of our PDMII based devices reached 10.89% and was maintained at 90% after 210 days of air storage.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High efficiency colloidal quantum solar cells (10.99%) using iodide-exchanged quantum dots. </LI> <LI> Efficient reduction of surface trap-states of quantum dots using novel iodide source, PDMII. </LI> <LI> Unprecedentedly high air stability of devices due to improved surface passivation. </LI> <LI> Exceptionally low energy loss in devices using PDMII-exchanged quantum dots. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Highly passivated PbS CQDs were developed using a novel iodide based ligand, 1-propyl-2,3-dimethylimidazolium iodide (PDMII). The effects of PDMII on the surface quality of PbS-CQDs were investigated. By using PDMII, improved surface passivation with reduced sub-bandgap trap-states was achieved. Solar cell devices using our PDMII based CQDs displayed state-of-the-art PCE (10.99%) and air stability with low energy loss (0.447eV).</P> <P>[DISPLAY OMISSION]</P>