Nara Cho

Efficient and stable panchromatic squaraine dyes for dye-sensitized solar cells

A new series of stable, unsymmetrical squaraine near-IR sensitizers (JK-216 and JK-217), which are assembled using both thiophenyl pyrrolyl and indolium groups, exhibit a panchromatic light harvesting up to 780 nm. The JK-216 based cell exhibited a record efficiency of 6.29% for near-IR DSSCs. In addition, the JK-217 device showed an excellent stability under a light soaking test at 60 °C for 1000 h.

New type of organic sensitizers with a planar amine unit for efficient dye-sensitized solar cells.

A new type of organic sensitizers incorporating a planar amine unit have been synthesized and demonstrated to be a highly efficient sensitizers, showing evidence of lateral interactions on the TiO(2) surface. Under standard global air mass 1.5 solar conditions, the JK-98 sensitized cell gave a short circuit photocurrent density (J(sc)) of 16.78 mA cm(-2), an open-circuit voltage (V(oc)) of 0.745 V, and a fill factor (ff) of 0.70, corresponding to an overall conversion efficiency (η) of 8.71%.

Synthesis of annulated thiophene perylene bisimide analogues: their applications to bulk heterojunction organic solar cells

Annulated thiophene perylene bisimides and their triphenyl-amine based oligomers have been synthesized. One of the oligomers FPTTPA has been demonstrated to be an efficient electron donor in bulk heterojunction (BHJ) organic solar cells, giving a power conversion efficiency of 1.42%.

Facile Synthesis of Fluorine‐Substituted Benzothiadiazole‐Based Organic Semiconductors and Their Use in Solution‐Processed Small‐Molecule Organic Solar Cells

A facile new protocol for the synthesis of iodinated derivatives of fluorinated benzothiadiazoles is demonstrated for the production of p-type semiconducting materials. The newly synthesized small-molecule compounds bis[TPA-diTh]-MonoF-BT and bis[TPA-diTh]-DiF-BT exhibited a power conversion efficiency of 2.95% and a high open-circuit voltage of 0.85 V in solution-processed small-molecule organic solar cells.

Planar star-shaped organic semiconductor with fused triphenylamine core for solution-processed small-molecule organic solar cells and field-effect transistors.

The symmetrical planar star-shaped organic semiconductor DMM-TPA-[DTS(BTTh(3))](3) with fused TPA core donor and three branch motifs, DTS(BTTh(3)), exhibited efficient p-type semiconducting performance in solution-processed SMOSCs and OFETs compared to the tilted star-shaped TPA-[DTS(BTTh(3))](3); a noteworthy PCE value of 4.16% was observed, with a hole mobility and on/off ratio of 7.6 × 10(-3) cm(2) V(-1) s(-1) and 5 × 10(6), respectively.

New Organic Dye Based on a 3,6-Disubstituted Carbazole Donor for Efficient Dye-Sensitized Solar Cells

We have synthesized and characterized four organic dyes (H1-H4) based on a 3,6-disubstituted carbazole donor as sensitizers in dye-sensitized solar cells. These dyes have high molar extinction coefficients and energy levels suitable for electron transfer from an electrolyte to nanocrystalline TiO(2) particles. Under standard air mass 1.5 global (AM 1.5 G) solar irradiation, a device using dye H4 exhibits a short-circuit current density (J(sc)) of 13.7 mA cm(-2), an open-circuit voltage (V(oc)) of 0.68 V, a fill factor (FF) of 0.70, and a calculated efficiency of 6.52%. This performance is comparable to that of a reference cell based on N719 (7.30%) under the same conditions. After 1000 hours of visible-light soaking at 60 °C, the overall efficiency remained at 95% of the initial value.

Efficient small molecule organic semiconductor containing bis-dimethylfluorenyl amino benzo[ b ]thiophene for high open circuit voltage in high efficiency solution processed organic solar cell

A new small molecule organic semiconductor, bisDMFABT-Th-MMN, containing a benzothiophene donor and methylene-malononitrile acceptor, exhibited high power conversion efficiency of 4.01% with a high open circuit voltage of 0.95 V in solution processed small molecule organic solar cells.

Synthesis, optical and electrochemical properties of small molecules DMM-TPA[DTS(FBTTh3)3] and TPA[DTS(FBTTh3)3], and their application as donors for bulk heterojunction solar cells

Two symmetrical planar star-shaped organic small molecules, i.e., DMM-TPA[DTS(FBTTh3)3] (1) and TPA[DTS(FBTTh3)3] (2), with fused TPA and TPA core donors, respectively, and three branched DTS(FBTTh3) units were synthesized and characterized. These small molecules were used donor materials along with a PC71BM acceptor for solution-processed bulk heterojunction solar cells. The power conversion efficiency (PCE) of the solar cells based on 1 and 2 is about 2.87% and 2.51%, respectively, when the active layers were processed from a CB solvent. The higher PCE of the solar cell based on 1 may be attributed to its low bandgap and broad absorption profile as compared to 2. The PCE of the solution-processed SMBHJ solar cells was improved up to 5.16% and 4.70% for 1 and 2, respectively, when the active layers were processed with 4 v% DIO as an additive in the CB solvent. The enhancement in the PCE was mainly due to the increase in Jsc and FF, which is attributed to the balanced charge transport between the electron and hole transport and reduction in the bimolecular recombination, leading to an increase in the PCE.

Stepwise cosensitization through chemically bonding organic dye to CdS quantum-dot-sensitized TiO2 electrode

An organic dye (JK218) with thiol moiety as an anchoring group was synthesized and explored to assemble a cosensitized TiO2 electrode in combination with an inorganic CdS quantum-dot. Due to the selective adsorption of JK218 on the surface of CdS through thiol group, the developed cosensitized electrode demonstrates cascade architecture with CdS coating on TiO2 while JK218 functions as a covering on CdS. Most importantly, the energy levels of the TiO2–CdS-JK218 electrode were also found to be stepwise aligned, which accordingly makes electrons efficiently inject from JK218 to CdS under illumination and finally collect to TiO2. This constructed cosensitized electrode with an organic sensitizer (JK218) and an inorganic quantum-dot (CdS) being selectively bonded together is expected to be valuable for the interface design of next generation solar cells.