Hobeom Kim

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Employing 2D-Perovskite as an Electron Blocking Layer in Highly Efficient (18.5%) Perovskite Solar Cells with Printable Low Temperature Carbon Electrode

Dmitry Bogachuk, Hiroyuki Kanda, Hobeom Kim, Mohammad Khaja Nazeeruddin, So-Min Yoo

Interface engineering and passivating contacts are key enablers to reach the highest efficiencies in photovoltaic devices. While printed carbon-graphite back electrodes for hole-transporting material (HTM)-free perovskite solar cells (PSCs) are appealing for fast commercialization of PSCs due to low processing costs and extraordinary stability, this device architecture so far suffers from severe performance losses at the back electrode interface. Herein, a 2D perovskite passivation layer as an electron blocking layer (EBL) at this interface to substantially reduce interfacial recombination losses is introduced. The formation of the 2D perovskite EBL is confirmed through X-ray diffraction, photoemission spectroscopy, and an advanced spectrally resolved photoluminescence microscopy mapping technique. Reduced losses that lead to an enhanced fill factor and V-OC are quantified by electrochemical impedance spectroscopy and J(SC)-V-OC measurements. This enables reaching one of the highest reported efficiencies of 18.5% for HTM-free PSCs using 2D perovskite as an EBL with a significantly improved device stability.

WILEY-V C H VERLAG GMBH2022

Here, we report photonic nanostructures replicated from the adaxial epidermis of flower petals onto light-polymerized coatings using low-cost nanoimprint lithography at ambient temperature. These multifunctional nanocoatings are applied to confer enhanced light trapping, water repellence, and UV light and environmental moisture protection features in perovskite solar cells. The former feature helps attain a maximum power conversion efficiency of 24.61% (21.01% for the reference cell) without any additional de-vice optimization. Added to these merits, the nanocoatings also enable stable operation under AM 1.5G and UV light continuous illumination or in real-world conditions. Our engineering approach provides a simple way to produce multifunctional nanocoatings optimized by nature's wisdom.

ELSEVIER2022

Phase-Pure Quasi-2D Perovskite by Protonation of Neutral Amine

Marc Dessimoz, Cansu Igci, Hiroyuki Kanda, Hobeom Kim, Mohammad Khaja Nazeeruddin, So-Min Yoo

Phase control of low-dimensional metal-halide perovskites (LDPs) greatly affects their optoelectronic properties, and phase-pure LDPs are desirable to achieve efficient perovskite optoelectronic devices such as solar cells and light-emitting diodes. Herein, we introduce a method to obtain phase-pure LDP by using a neutral amine, cyclohexylmethyl amine (CHMA). The incorporation of CHMA into a formamidinium lead bromide (FAPbBr(3)) precursor solution leads to the protonation of the amine that allows the phase transition of 3D FAPbBr(3) to phase-pure quasi-2D perovskite (n = 2). For comparison, cyclohexylmethylammonium bromide (CHMABr), which is a conventional form of ammonium halide salt with the same organic moiety to the amine, is used, which resulted in a 2D perovskite (n = 1). The perovskite films fabricated by the two different methodologies are characterized. This study paves the way for further research on the realization of phase-pure perovskites and their relevant optoelectronic devices.

AMER CHEMICAL SOC2021