Dong Geon Lee

Efficient Carrier Separation and Intriguing Switching of Bound Charges in Inorganic–Organic Lead Halide Solar Cells

We fabricated a mesoporous perovskite solar cell with a ∼14% conversion efficiency, and we investigated its beneficial grain boundary properties of the perovskite solar cells through the use of scanning probe microscopy. The CH3NH3Pb(I0.88,Br0.12)3 showed a significant potential barrier bending at the grain boundary and induced passivation. The potential difference value in the x = 0.00 sample is ∼50 mV, and the distribution of the positive potential is lower than that of the x = 0.12 sample. We also investigated the polarization and hysteretic properties of the perovskite thin films by measuring the local piezoresponse. Specifically, the charged grain boundaries play a beneficial role in electron-hole depairing and in suppressing recombination in order to realize high-efficiency perovskite solar cells.

Green-emitting Lu3Al5O12:Ce3+ phosphor as a visible light amplifier for dye-sensitized solar cells

A down convertor Lu3Al5O12:Ce3+ (LuAG) phosphor was used as a visible light amplifier for dye-sensitized solar cells (DSSCs). LuAG particles emitting green light with a wavelength of 470 to 650 nm, which is capable of stimulating Ru-dye molecules, enhanced the light-harvesting properties of a DSSC. The average short-circuit current density (Jsc) of the DSSC containing LuAG down conversion layers was approximately 9.6% higher than that of the mesoporous (mp) TiO2-based DSSC. Therefore, the average power conversion efficiency (PCE) for the DSSC with LuAG was 7.5% under AM 1.5 conditions, which was 8.7% higher than that for the mp-TiO2 based DSSC. The superior photovoltaic properties of the DSSC containing LuAG down conversion layers under UV light illumination revealed the effective wavelength down-converting properties of the LuAG down conversion layers.

Antisolvent with an Ultrawide Processing Window for the One-Step Fabrication of Efficient and Large-Area Perovskite Solar Cells

Photovoltaic technologies based on perovskite absorber materials have led this optoelectronic field into a brand-new horizon. However, the present antisolvents used in the one-step spin-coating method always encounter problems with the very narrow process window. Herein, anisole is introduced into the one-step spin-coating method, and the technology is developed to fabricate perovskite thin films with ultrawide processing window with a dimethylformamide (DMF):dimethyl sulfoxide (DMSO) ratio varying from 6:4 to 9:1 in the precursor solution, anisole dripping time ranging from 5 to 25 s, and an antisolvent volume varying from 0.1 to 0.9 mL. Perovskite thin films as large as 100 cm2 are successfully fabricated using this method. Maximum photoelectric conversion efficiencies of 19.76% for small-area (0.14 cm2 ) and 17.39% for large-area (1.08 cm2 ) perovskite solar cell devices are obtained. It is also found that there are intermolecular hydrogen-bonding forces between anisole and DMF/DMSO that play critical roles in the wide process window. These results provide a deeper understanding of the crystallizing procedure of perovskite during the one-step spin-coating process.