Grown Nanocrystalline Si Recombination Junction Layers for Efficient Perovskite-Si Monolithic Tandem Solar Cells: Toward a Simpler Multijunction Architecture.

The perovskite-Si tandem is an attractive avenue to attain greater power conversion efficiency (PCE) than their respective single-junction solar cells. However, such devices generally employ complex stacks with numerous deposition steps, which are rather unattractive from an industrial perspective. Here, we develop a simplified tandem architecture consisting of a perovskite n-i-p stack on a silicon heterojunction structure without applying the typically used indium-tin-oxide (ITO) recombination junction (RJ) layer between the top and bottom cells.

A Sodium Chloride Modification of SnO Electron Transport Layers to Enhance the Performance of Perovskite Solar Cells.

A sodium chloride modification was applied where different amounts of sodium chloride was physically blended in a tin oxide colloid solution to passivate the interface between the electron transport layer (ETL) and perovskite layer and improve the performance of perovskite solar cells. Sodium chloride-modified tin oxide was utilized as the electron transport material to fabricate perovskite solar cells. It was found that sodium chloride-modified tin oxide as an ETL could considerably enhance the performance of the device compared to pristine tin oxide.

Insights into Microscopic Crystal Growth Dynamics of CHNHPbI under a Laser Deposition Process Revealed by X-ray Diffraction.

The process dynamics for the vacuum deposition of methylammonium lead iodide (MAPbI) perovskite was analyzed by X-ray diffraction using synchrotron radiation. MAPbI was fabricated by alternatingly supplying PbI and methylammonium iodide a laser deposition system installed at the synchrotron beamline BL46XU at SPring-8, and crystallization analysis was conducted. Microscopic insights into the crystallization were obtained, including observation of Laue oscillation during the PbI growth and octahedral unit (PbI) rotation during the transformation into perovskite.

Cesium iodide post-treatment of organic-inorganic perovskite crystals to improve photovoltaic performance and thermal stability.

Organic-inorganic perovskites were treated with a CsI solution to improve the photovoltaic performance and stability. Due to the formation of CsPbI3 and trap filling in Cs0.05(FA0.

Electron band tuning of organolead halide perovskite materials by methylammonium and formamidinium halide post-treatment for high-efficiency solar cells.

Perovskite crystals post-treated with methylammonium and formamidinium halide materials were compared. The bandgap energy of perovskites changed upon incorporation of CH5N2+, Br-, and Cl- ions. Perovskites treated with formamidinium iodide yielded the best efficiency of 20.

Tuning Methylammonium Iodide Amount in Organolead Halide Perovskite Materials by Post-Treatment for High-Efficiency Solar Cells.

In this study, the composition of organic-inorganic perovskite materials is tuned by methylammonium iodide (MAI) post-treatment for high photovoltaic performance. By spin-coating MAI solutions of different concentrations, the amounts of PbI and MAI in perovskite layers are tuned. In perovskites, the removal of PbI through a reaction with MAI decreases the hysteresis in photocurrent density-voltage curves.

Constructing Nanostructured Donor/Acceptor Bulk Heterojunctions via Interfacial Templates for Efficient Organic Photovoltaics.

We demonstrate that a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/diindenoperylene (PEDOT:PSS/DIP) interfacial bilayer could serve as a structural template to enable the morphological control of bulk heterojunctions (BHJs) by co-evaporation of tetraphenyldibenzoperiflanthene:fullerene (DBP:C), which greatly improves the device performances. Especially, we show that isolated crystalline domains of C can be well-controlled at the nanoscale during the co-evaporation. Photoluminescence spectra indicate the realization of DIP/DBP cascade energy architecture, which significantly facilitates both the energy transfer and photocurrent generation.

Adjustment of Conduction Band Edge of Compact TiO Layer in Perovskite Solar Cells Through TiCl Treatment.

Perovskite solar cells (PSCs) without a mesoporous TiO layer, that is, planar-type PSCs exhibit poorer cell performance as compared to PSCs with a porous TiO layer, owing to inefficient electron transfer from the perovskite layer to the compact TiO layer in the former case. The matching of the conduction band levels of perovskite and the compact TiO layer is thus essential for enhancing PSC performance. In this study, we demonstrate the shifting of the conduction band edge (CBE) of the compact TiO layer through a TiCl treatment, with the aim of improving PSC performance.

Highly Controlled Codeposition Rate of Organolead Halide Perovskite by Laser Evaporation Method.

Organolead-halide perovskites can be promising materials for next-generation solar cells because of its high power conversion efficiency. The method of precise fabrication is required because both solution-process and vacuum-process fabrication of the perovskite have problems of controllability and reproducibility. Vacuum deposition process was expected to achieve precise control; however, vaporization of amine compound significantly degrades the controllability of deposition rate.

Crystallization Dynamics of Organolead Halide Perovskite by Real-Time X-ray Diffraction.

We analyzed the crystallization process of the CH3NH3PbI3 perovskite by observing real-time X-ray diffraction immediately after combining a PbI2 thin film with a CH3NH3I solution. A detailed analysis of the transformation kinetics demonstrated the fractal diffusion of the CH3NH3I solution into the PbI2 film. Moreover, the perovskite crystal was found to be initially oriented based on the PbI2 crystal orientation but to gradually transition to a random orientation.

Understanding device-structure-induced variations in open-circuit voltage for organic photovoltaics.

We investigate the structural influences on the device performance, especially on open-circuit voltage (V(OC)) in squaraine (SQ)/fullerene (C60) bilayer cells. Simply changing the SQ thickness could lead to 40% variation in V(OC) from 0.62 to 0.

Simple push coating of polymer thin-film transistors.

Solution processibility is a unique advantage of organic semiconductors, permitting the low-cost production of flexible electronics under ambient conditions. However, the solution affinity to substrate surfaces remains a serious dilemma; liquid manipulation is more difficult on highly hydrophobic surfaces, but the use of such surfaces is indispensable for improving device characteristics. Here we demonstrate a simple technique, which we call 'push coating', to produce uniform large-area semiconducting polymer films over a hydrophobic surface with eliminating material loss.

Soluble fullerene-based n-channel organic thin-film transistors printed by using a polydimethylsiloxane stamp.

A polydimethylsiloxane stamp was applied for the first time to the fabrication of n-channel thin-film transistors based on soluble small molecule organic semiconducting materials. The stamping method was found to facilitate film transfer onto a gate insulator surface irrespective of its surface free energy. We used [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) and C(60)-fused N-methylpyrrolidine-meta-dodecyl phenyl (C60MC12) as n-channel materials.

Crystal structure of friction-transferred poly(2,5-dioctyloxy-1,4-phenylenevinylene).

Poly(2,5-dioctyloxy-1,4-phenylenevinylene) (DOPPV) was found to form a highly oriented film by a friction-transfer technique. Structural investigation of friction-transferred DOPPV was studied by means of polarized ultraviolet-visible (UV-vis) absorption spectroscopy, polarized photoluminescence (PL) spectroscopy, and synchrotron-sourced grazing incident X-ray diffraction (GIXD) analysis. The polarized UV-vis absorption and PL spectra indicate clear axial alignment.