Hyo Jeong Jo

Perspective: Understanding of ripening growth model for minimum residual PbI2 and its limitation in the planar perovskite solar cells

The power conversion efficiency of lead halide perovskite solar cells recently surpassed 22.1%. In this study, we suggest the perovskite absorber growth mechanism of the two-step process could be explained by an Ostwald ripening growth model for planar-structure perovskite solar cells. We attempt to find out the source of two main problems such as unreacted PbI2 and non-uniformed morphology by the proposed ripening growth mechanism and experimental results. This growth mechanism opens the way toward understanding a key aspect of the photovoltaic operation of high-efficiency, two-step perovskite solar cells.

Molecular Design and Photovoltaic Performances of Organic Dyes Containing Triphenylamine for Dye-Sensitized Solar Cell

Organic dyes containing multi-acceptors/anchors in a chromophore were synthesized for use in a dye-sensitized solar cell. The photovoltaic properties of organic dyes composed of different acceptor in their chromophores were measured to identify the effects on the DSSC performance. The organic dye, 4 containing multi-cyanoacrylic acid as the electron acceptor showed a power conversion efficiency of 4.7% under AM 1.5 illumination (100 mW cm−2) in an photo active area of 0.24 cm2, short circuit current density of 12.9 mA cm−2, open circuit photo voltage of 0.62 V and a fill-factor of 60%. The retarded recombination kinetics from TiO2 electrode to electrolyte enhanced the electron life time of organic dye, 4 in the photoanode in DSSC that was well confirmed with the impedance analysis.

Controlled growth of organic–inorganic hybrid CH3NH3PbI3 perovskite thin films from phase-controlled crystalline powders

High-quality CH3NH3PbI3 (MAPbI3) crystalline powders were synthesized from a dispersion of MAPbI3 solution (solvent: N,N-dimethylformamide (DMF)) in the antisolvent dichloromethane. They were used as starting chemicals for precursor solutions. The PbI2–DMF-, perovskite-, and PbI2–MAI (methylammonium iodide)–DMF-dominant phases were preferentially formed under conditions of excess PbI2, moderate, and high-excess MAI input ratios, respectively. The input ratio of powders in fabricating the thin MAPbI3 films strongly affected not only the morphology and structure of the films, but also the photovoltaic performance of the devices using them. The devices were constructed as follows: Au/hole-transporting material/MAPbI3/mesoporous TiO2 layer/TiO2 blocking layer/F-doped SnO2. The best device performance was obtained from the powder with a specific ratio of PbI2 : MAI = 1 : 1.6; the device exhibited a power conversion efficiency of ∼16% at 1.5G standard conditions. Our proposed method could provide a simple and versatile solution-based approach for a low-cost perovskite solar cell fabrication technology.

Structure-Property Relationship of New Organic Sensitizers Based on Multicarbazole Derivatives for Dye-Sensitized Solar Cells

A new multicarbazole based organic dye (C2A1, C2S1A1) with a twisted structure was designed and synthesized, and the corresponding dye (C1A1) without the twisted structure was synthesized for comparison. They were successfully applied in dye-sensitized solar cells (DSSCs). The results showed that the nonplanar structure of C2A1 and C2S1A1 can efficiently retard the dye aggregation and charge recombination. The organic dye (C2S1A1) with thiophene units also exhibited a higher molar extinction coefficient and red-shifted absorption, which leads to an improved light harvesting efficiency. The C2S1A1-sensitized solar cell produced a solar-to-electricity conversion efficiency of 5.1%, high open circuit voltage () of 0.69 V, and short-circuit photocurrent density of 10.83 mA cm−2 under AM 1.5 irradiation (100 mW cm−2) conditions.

Effect of Anti-Reflective Layer in Dye-Sensitized Solar Cells

Anti-reflective (AR) layers play an important role in boosting the amount of light entering a device and reducing reflection losses in a device, thereby enhancing the power conversion efficiency of solar cells. We have coated an AR layer on the surface of a dye-sensitized solar cell device by using an electron beam evaporation system and investigated the effects of the AR layer by measuring photovoltaic performance. The AR layer is found to increases the Jsc and η of the solar cell.

Growth of Cu 2 ZnSnSe 4 thin films by spin-coating and selenization process

Cu2ZnSnSe4 (CZTS) thin films were prepared by a solution-based process and selenization. The solution-based process involved spin-coating, and the selenization was performed by a rapid thermal process. The solution-based process is cost-effective compared to the vacuum-based manufacturing process, which uses expensive vacuum equipment. A ternary Cu-Zn-Sn precursor solution is used to deposit precursor layers prior to selenization, and the selenization was controlled by adjusting the temperature. The structural, morphological and optical properties of the grown CZTS thin films were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectroscopy, respectively. The process of CZTS thin film preparation by the spin-coating technique is shown to be a useful process for controlling the chemical composition of thin films and preparing high-quality thin film solar cells.

Preparation of CuInSe 2 solar cell films using CuInSe 2 /InSe nano-particle ink

A non-vacuum process for the fabrication of a CISe absorber layer from nano-particle ink is described. CISe and InSe nano-particles were prepared via sonochemical synthesis by reacting the starting materials. We prepared nano-particle inks by using an organic binder or various solvents to obtain high-quality thin films. The nano-particle ink was used for the deposition process of precursor thin films; the selenization of the precursor thin films was performed. In order to control the composition of volatile Se in the CISe absorber layer, a bi-layer structure of the precursor thin films is proposed. By using an additional top-layer containing elemental Se, the composition of Se in the CISe absorber layer was maintained after the selenization process. In the case of the bi-layer precursor thin films, unnecessary elements in the top-layer were unfavorable for grain growth and the morphology of the CISe absorber layer.