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Interface engineering is critical for reducing trap states present in various device interfaces and improving the efficiency of perovskite solar cells (PSCs). This study introduces the blending effect of poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) into metal‐phthalocyanine−tetrasulfonated acid tetrasodium salt (TS‐MPc) used as a hole transport layer (HTL) in organic–inorganic hybrid PSCs. PEDOT:PSS with a low pH induces the self‐assembly and formation of mesh‐like nano‐networks in a TS‐MPc layer, which is confirmed by atomic force microscopy and elemental mapping using energy‐dispersive spectroscopy. Compared with pure TS‐MPc, nano‐networked TS‐MPc with PEDOT:PSS exhibits higher crystallinity by grazing‐incidence wide‐angle X‐ray scattering. The nano‐network formation contributes to ≈30% enhancement in the power conversion efficiency (14.65%) of device with PEDOT:PSS‐assisted TS‐CuPc as HTL, compared with device using conventional PEDOT:PSS (11.02%). In addition, the device with PEDOT:PSS‐assisted TS‐MPc shows a significant improvement in stability owing to the reduced pH of the HTL compared with the device using pristine PEDOT:PSS. [ABSTRACT FROM AUTHOR]

Tunable and selective areal polymer chain alignment method is developed for spin-cast blend films of poly(3-hexylthiophene)(P3HT):[6,6]-phenyl-C61-butlyric methyl ester (PCBM) system by a femtosecond laser process. The chain alignment, phase separation, and molecular structure of the laser exposed P3HT:PCBM films are investigated by grazing incidence wide angle X-ray scattering and micro-Raman analysis. The alkyl chains of P3HT polymer become highly ordered along the polarization axis of the laser. Thus, the amount of desirable face-on configuration for solar cell application is largely enhanced with a subsequent postannealing process. Vertically expanded morphology up to 200 nm on P3HT:PCBM films is also prompted by the laser irradiation without deteriorating intramolecular structure and changing chemical composition. Simultaneously, vertical phase separation of PCBM toward surface is induced at exposed region. [ABSTRACT FROM AUTHOR]

This work reports the self-organization of dimple nanostructures on a polyethylene naphthalate (PEN) surface where an Ar ion beam was irradiated at an ion energy of 600 eV. The peak-to-peak roughness and diameter of dimple nanostructures were 29.1~53.4 nm and 63.4~77.6 nm, respectively. The electron energy loss spectrum at the peaks and troughs of dimples showed similar C=C, C=O, and O=CH bonding statuses. In addition, wide-angle X-ray scattering showed that Ar ion beam irradiation did not induce crystallization of the PEN surface. That meant that the self-organization on the PEN surface could be due to the ion-induced surface instability of the amorphous layer and not due to the partial crystallinity differences of the peaks and valleys. A nonlinear continuum model described surface instability due to Ar ion-induced sputtering. The Kuramoto–Sivashinsky model reproduced the dimple morphologies numerically, which was similar to the experimentally observed dimple patterns. This preliminary validation showed the possibility that the continuum equation used for metal and semiconductor surfaces could be applied to polymer surfaces where ion beam sputtering occurred. [ABSTRACT FROM AUTHOR]

[Display omitted] • Slow crystallization for high oriented perovskite crystals in ambient air. • 18.56% of MAPbI 3 PV has been achieved under the optimal air-process condition. • Optimal device retained over 90% of initial performance after 914 h in dry air. Although the efficiency of inorganic-organic perovskite solar cells (PSCs) has increased significantly owing to intermediate phase induced slow crystallization using dimethyl sulfoxide (DMSO) as a co-solvent in N 2 -filled glovebox, PSCs are generally fabricated in ambient air via a fast crystallization process to protect the perovskite layer from H 2 O or O 2. In this study, we suggest a possibility of slow crystallization process for MAPbI 3 perovskite crystals via intermediate phase formation by adjusting the humidity of air at RH 20%–30%. We obtained high-quality perovskite grains by implementing the slow crystallization process using an antisolvent and the ratio of PbI 2 :MAI:DMSO in the precursor solution at RH 20%–30%. The amount and state of the intermediate phase inside the as-deposited film were analyzed by grazing incidence wide-angle X-ray scattering (GIWAXS) measurements. The deposited perovskite layer with the pure intermediate via extremely slow crystallization showed higher absorption, fewer grain boundaries, and suppressed defect recombination losses than the fast crystallized perovskite phase. Thus, we obtained higher stability and high power conversion efficiency of up to 18.56% in a p-i-n-structured MAPbI 3 -based perovskite solar cell under ambient air with RH 20%–30%. [ABSTRACT FROM AUTHOR]

We found that micro-cells surrounded by nanowalls can be formed by a maskless wet-etching process on Si (100) surfaces possessing Laser Induced Periodic Surface Structure (LIPSS) by femtosecond laser irradiation. The LIPSS process could produce periodic one-dimensional micron scale ripples on a Si surface, which could be developed into micro-cells by a subsequent etching process. The solution etching conditions strongly affected both the micro-cell and nanowall shapes such as the height and the thickness of nanowalls. The tetramethylammonium hydroxide solution created thin nanowalls and the resulting micro-cells with a well-flattened bottom while the KOH solution formed thick walls and incomplete micro-cells. The bottoms of micro-cells surrounded by the nanowalls were considerably flat with a 3.10 nm surface roughness. A pentacene layer was deposited on the micro-cells of a Si surface to evaluate the film properties by grazing incidence wide angle x-ray scattering measurements. The pentacene film on the micro-cell Si surface showed a strong film phase, which was comparable to the film phase grown on the atomically flat Si surface. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the effects of ZnO annealing temperature (T A ) on the performance of inverted polymer solar cells with ZnO electron-selective layers deposited by spin coating aqueous solutions of an ammine-hydroxo zinc complex. The inverted solar cells based on poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester with T A as low as 80°C exhibit power-conversion efficiencies of 3.6%, which is equal to those of devices with higher T A . Characterizations of the ZnO films using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, grazing incidence wide-angle X-ray scattering, and optical transmittance measurements show that the abrupt improvement of device performance from T A =60 to 80°C is due to the improvement of energy-level alignment arising from the increases in the relative amount and the crystallinity of ZnO. [Copyright &y& Elsevier]