Byoungwook Park

Achieving Large‐Area Planar Perovskite Solar Cells by Introducing an Interfacial Compatibilizer

Despite the recent unprecedented increase in the power conversion efficiencies (PCEs) of small-area devices (≤0.1 cm2 ), the PCEs deteriorate drastically for PSCs of larger areas because of the incomplete film coverage caused by the dewetting of the hydrophilic perovskite precursor solutions on the hydrophobic organic charge-transport layers (CTLs). Here, an innovative method of fabricating scalable PSCs on all types of organic CTLs is reported. By introducing an amphiphilic conjugated polyelectrolyte as an interfacial compatibilizer, fabricating uniform perovskite films on large-area substrates (18.4 cm2 ) and PSCs with the total active area of 6 cm2 (1 cm2 × 6 unit cells) via a single-turn solution process is successfully demonstrated. All of the unit cells exhibit highly uniform PCEs of 16.1 ± 0.9% (best PCE of 17%), which is the highest value for printable PSCs with a total active area larger than 1 cm2 .

Organic Single‐Crystal Semiconductor Films on a Millimeter Domain Scale

Nucleation and growth processes can be effectively controlled in organic semiconductor films through a new concept of template-mediated molecular crystal seeds during the phase transition; the effective control of these processes ensures millimeter-scale crystal domains, as well as the performance of the resulting organic films with intrinsic hole mobility of 18 cm(2) V(-1) s(-1).

Optically transparent semiconducting polymer nanonetwork for flexible and transparent electronics

Significance When various electronic appliances used in everyday life become deformable and transparent, they will provide tremendous versatility in the design and use of see-through, smart mobile applications, exceeding the limitations of the best developed conventional silicon technologies, which are available only in rigid, opaque forms. However, even recently discovered innovative semiconducting components have failed to simultaneously achieve such flexibility and transparency. Thus, the existing options still comprise only hard, planar, or opaque materials, and obtaining a “key” material for creating truly flexible and transparent electronics has presented a formidable challenge. We report an effective means of creating a “truly flexible, perfectly transparent” and high-mobility semiconducting material and demonstrate several high-end flexible and transparent applications based on a polymeric semiconductor system. Simultaneously achieving high optical transparency and excellent charge mobility in semiconducting polymers has presented a challenge for the application of these materials in future “flexible” and “transparent” electronics (FTEs). Here, by blending only a small amount (∼15 wt %) of a diketopyrrolopyrrole-based semiconducting polymer (DPP2T) into an inert polystyrene (PS) matrix, we introduce a polymer blend system that demonstrates both high field-effect transistor (FET) mobility and excellent optical transparency that approaches 100%. We discover that in a PS matrix, DPP2T forms a web-like, continuously connected nanonetwork that spreads throughout the thin film and provides highly efficient 2D charge pathways through extended intrachain conjugation. The remarkable physical properties achieved using our approach enable us to develop prototype high-performance FTE devices, including colorless all-polymer FET arrays and fully transparent FET-integrated polymer light-emitting diodes.

A highly efficient self-power pack system integrating supercapacitors and photovoltaics with an area-saving monolithic architecture

Self-charging power packs (SPPs), integrating both a solar cell and energy storage capacitor (EC) into a single device, are very promising energy systems due to their multiple functions of energy harvesting and storage. Despite their promising potential, however, the monolithic stacking of solid-state ECs onto a large-area solar cell without any external wires is one of the crucial challenges. Here, we successfully demonstrate compact and monolithically stacked SPPs combining a polyvinyl alcohol (PVA)/phosphoric acid (H3PO4)-based solid-state supercapacitor and an organometal halide perovskite- or polymer-based solar cell (PeSC or PSC). As a result of robust interconnection formed via a novel electric glue and efficient solar cells with an enlarged photo-harvesting area of up to 100 mm2, the SPPs exhibited a very high storage efficiency (ηstorage) and overall efficiency (ηoverall) of 80.31% and 10.97%, respectively, for the PeSC-supercapacitor power pack, and 64.59% and 5.07%, respectively, for the PSC-supercapacitor power pack. To the best of our knowledge, the ηoverall value of our PeSC-supercapacitor power pack is by far the highest reported efficiency for integrated self-charging power packs.

Synthesis and organic field effect transistor properties of isoindigo/DPP-based polymers containing a thermolabile group

(E)-6,6′-Dibromo-1,1-bis(2-octyldodecyl)-(3,3′-biindolinylid-ene)-2,2′-dione and/or 2,5-bis(2-octyldodecyl)-3,6-di(5-bromothien-2-yl)pyrrolo[3,4-c]pyrrole-1,4-(2H,5H)-dione and their tBoc-counterparts were propagated with 2,5-bis(tributylstannyl)thiophene in a molar ratio of 0.8 : 0.2 : 1.0 to release P(ODIDT-BID), P(ODIDT·BDPP), P(ODDPPT·BID) and P(ODDPPT·BDPP) as a new series of random conjugated polymers (RCPs) bearing a large number of octyldodecyl chains to ensure solubility and a small number of thermocleavable tBoc function to cast H-bonding upon heating up to 220 °C. All new polymers were synthesised via Pd catalysed Stille cross-coupling methodology in high yields and reasonable average molecular weights. The cast polymer films exhibited considerable red-shifted UV-vis absorption spectra and a further red-shift was also obtained in the thermal annealed films (at 220 °C for 30 min), which reflected the increasing of crystalline structure. The formation of H-bonding in these polymers was investigated using X-ray diffractometry (XRD) measurements. The field-effect mobilities of these polymers were investigated in the configuration of bottom-gate and bottom-contact (BGBC) field-effect transistors (FETs). The results from FETs indicated that the crystalline structure of RCPs exhibited reasonable FET mobilities with 1.17 × 10−3 cm2 V−1 s−1 for P(ODDPPT·BID) and 1.41 × 10−3 cm2 V−1 s−1 for P(ODDPPT·BDPP).

Highly Deformable and See‐Through Polymer Light‐Emitting Diodes with All‐Conducting‐Polymer Electrodes

Despite the high expectation of deformable and see-through displays for future ubiquitous society, current light-emitting diodes (LEDs) fail to meet the desired mechanical and optical properties, mainly because of the fragile transparent conducting oxides and opaque metal electrodes. Here, by introducing a highly conductive nanofibrillated conducting polymer (CP) as both deformable transparent anode and cathode, ultraflexible and see-through polymer LEDs (PLEDs) are demonstrated. The CP-based PLEDs exhibit outstanding dual-side light-outcoupling performance with a high optical transmittance of 75% at a wavelength of 550 nm and with an excellent mechanical durability of 9% bending strain. Moreover, the CP-based PLEDs fabricated on 4 µm thick plastic foils with all-solution processing have extremely deformable and foldable light-emitting functionality. This approach is expected to open a new avenue for developing wearable and attachable transparent displays.

High-efficiency large-area perovskite photovoltaic modules achieved via electrochemically assembled metal-filamentary nanoelectrodes

We devised an electrochemical patterning process for large-area perovskite photovoltaic modules. Realizing industrial-scale, large-area photovoltaic modules without any considerable performance losses compared with the performance of laboratory-scale, small-area perovskite solar cells (PSCs) has been a challenge for practical applications of PSCs. Highly sophisticated patterning processes for achieving series connections, typically fabricated using printing or laser-scribing techniques, cause unexpected efficiency drops and require complicated manufacturing processes. We successfully fabricated high-efficiency, large-area PSC modules using a new electrochemical patterning process. The intrinsic ion-conducting features of perovskites enabled us to create metal-filamentary nanoelectrodes to facilitate the monolithic serial interconnections of PSC modules. By fabricating planar-type PSC modules through low-temperature annealing and all-solution processing, we demonstrated a notably high module efficiency of 14.0% for a total area of 9.06 cm2 with a high geometric fill factor of 94.1%.