Youn-Jung Heo

Toward Large Scale Roll‐to‐Roll Production of Fully Printed Perovskite Solar Cells

Fully printed perovskite solar cells are demonstrated with slot-die coating, a scalable printing method. A sequential slot-die coating process is developed to produce efficient perovskite solar cells and to be used in a large-scale roll-to-roll printing process. All layers excluding the electrodes are printed and devices demonstrate up to 11.96% power conversion efficiency. It is also demonstrated that the new process can be used in roll-to-roll production.

One-Step Printable Perovskite Films Fabricated under Ambient Conditions for Efficient and Reproducible Solar Cells

Despite the potential of roll-to-roll processing for the fabrication of perovskite films, the realization of highly efficient and reproducible perovskite solar cells (PeSCs) through continuous coating techniques and low-temperature processing is still challenging. Here, we demonstrate that efficient and reliable CH3NH3PbI3 (MAPbI3) films fabricated by a printing process can be achieved through synergetic effects of binary processing additives, N-cyclohexyl-2-pyrrolidone (CHP) and dimethyl sulfoxide (DMSO). Notably, these perovskite films are deposited from premixed perovskite solutions for facile one-step processing under a room-temperature and ambient atmosphere. The CHP molecules result in the uniform and homogeneous perovskite films even in the one-step slot-die system, which originate from the high boiling point and low vapor pressure of CHP. Meanwhile, the DMSO molecules facilitate the growth of perovskite grains by forming intermediate states with the perovskite precursor molecules. Consequently, fully printed PeSC based on the binary additive system exhibits a high PCE of 12.56% with a high reproducibility.

Slot-Die Coated Perovskite Films Using Mixed Lead Precursors for Highly Reproducible and Large-Area Solar Cells

Recently, many kinds of printing processes have been studied to fabricate perovskite solar cells (PeSCs) for mass production. Among them, slot-die coating is a promising candidate for roll-to-roll processing because of high-throughput, easy module patterning, and a premetered coating system. In this work, we employed mixed lead precursors consisting of PbAc2 and PbCl2 to fabricate PeSCs via slot-die coating. We observed that slot-die-coated perovskite films based on the mixed lead precursors exhibited well-grown and uniform morphology, which was hard to achieve by using only a single lead source. Consequently, PeSCs made with this precursor system showed improved device performance and reproducibility over single PbAc2. Lastly, a large-area module with an active area of 10 cm2 was fabricated with a power conversion efficiency of 8.3%.

A conjugated polymer with high planarity and extended π-electron delocalization via a quinoid structure prepared by short synthetic steps

An attractive synthetic strategy for incorporating a quinoidal molecule into a conjugated polymer backbone with three short steps is reported here. The quinoidal polymer, PQuBTV, exhibited high planarity and extended conjugation. As a result, ambipolar charge carrier mobilities of 0.52 cm2 V−1 s−1 for holes and 0.53 cm2 V−1 s−1 for electrons were observed in field-effect transistor devices.

Small-Molecule Organic Photovoltaic Modules Fabricated via Halogen-Free Solvent System with Roll-to-Roll Compatible Scalable Printing Method

For the first time, the photovoltaic modules composed of small molecule were successfully fabricated by using roll-to-roll compatible printing techniques. In this study, blend films of small molecules, BTR and PC71BM were slot-die coated using a halogen-free solvent system. As a result, high efficiencies of 7.46% and 6.56% were achieved from time-consuming solvent vapor annealing (SVA) treatment and roll-to-roll compatible solvent additive approaches, respectively. After successful verification of our roll-to-roll compatible method on small-area devices, we further fabricated large-area photovoltaic modules with a total active area of 10 cm2, achieving a power conversion efficiency (PCE) of 4.83%. This demonstration of large-area photovoltaic modules through roll-to-roll compatible printing methods, even based on a halogen-free solvent, suggests the great potential for the industrial-scale production of organic solar cells (OSCs).

A systematic study on molecular planarity and D–A conformation in thiazolothiazole- and thienylenevinylene-based copolymers for organic field-effect transistors

A new donor–acceptor type conjugated polymer (P1) composed of thiazolothiazole (TzTz) and thienylenevinylene (TV) units was synthesized to confirm that structural characteristics, such as the presence of coplanar units and a D–A conformation in the polymer main chain, can have an effect on charge carrier transport in high performance organic field-effect transistors. P1 was compared with two polymers that had bithiophene (BiTh) units instead of TV units (P2) or thienothiophene (TT) units in the place of TzTz units (P3) to investigate the relationship between the molecular structure and polymer properties. P1 had a higher order of orientation than P2 due to the rigid and planar structure caused by the presence of the TV unit in P1 compared to the distorted structure of P2. The effect of the D–A type configuration in P1 was also confirmed by demonstrating its stronger intermolecular interactions and more effective hole and electron transport compared with that of the D–D type polymer P3. Thus, in contrast to P2 (with a hole mobility of 0.076 cm2 V−1 s−1 and an electron mobility of 0.0025 cm2 V−1 s−1) and P3 (with a hole mobility of 0.2 cm2 V−1 s−1 only), P1 exhibited higher ambipolar charge carrier mobilities (1.66 cm2 V−1 s−1 of holes and 0.05 cm2 V−1 s−1 of electrons).