In this study, we explored the potential of exfoliated transition metal dichalcogenides (TMDs) as innovative spray-coated hole transport layers (HTLs) in organic photovoltaics (OPVs), addressing the need for efficient and stable materials in solar cell technology. This research was motivated by the need for alternative HTLs that can offer enhanced performance under varying lighting conditions, particularly in indoor environments. Employing UV-visible absorption and Raman spectroscopy, we characterized the optical properties of MoS2, MoSe2, WS2, and WSe2, confirming their distinct excitonic transitions and direct bandgap features. The nanocrystalline nature of these TMDs, revealed through XRD patterns and crystallite size estimation using the Scherrer method, significantly contributes to their enhanced physical properties and operational efficiency as HTLs in OPVs. These TMDs were then integrated into OPV devices and evaluated under standard solar and indoor lighting conditions, to assess their effectiveness as HTLs. The results demonstrated that MoS2, in particular, displayed remarkable performance, rivalling traditional HTL materials like MoO3. It maintained high power conversion efficiency across a spectrum of light intensities, illustrating its versatility for both outdoor and indoor applications. Additionally, MoS2 showed superior stability over extended periods, suggesting its potential for long-term usage in OPVs. This study contributes significantly to the field of photovoltaic materials, presenting TMDs, especially MoS2, as promising candidates for efficient and stable OPVs in diverse lighting conditions, thereby broadening the scope of solar cell applications.

The combination of chemically and structurally unstable hole transport materials (HTMs) and the metal ion diffusion from counter electrodes (CEs) toward the perovskite layer are reported as primary causes of the insufficient stability of perovskite solar cells (PSCs) and modules. Carbon-based CEs (C-CEs) directly deposited atop the perovskite layer without interposing any HTM represent a promising path to improving PSC stability while lowering the environmental impact and the manufacturing cost. In this work, we present a cost-effective approach to fabricating C-CEs using two different carbon pastes with distinct formulations, successfully replacing expensive metal-based electrodes. We engineered HTM-free PSCs based on a mesoscopic n-i-p structure and printable C-CEs (C-PSCs), with a 2D perovskite passivation layer as an electron-blocking layer between the perovskite and the C-CE. The devices using a low-temperature processed carbon counter electrode (LTPC-CE) improved the performance of the devices compared to the cells produced with a medium-temperature processed carbon counter electrode (MTPC-CE). This behavior is associated with enhanced charge carrier lifetime, charge transfer, and charge extraction processes enabled by effective solvent removal during the C-CE deposition as well as the highly electrically conductive pathways offered by graphene flakes. In particular, in small-area devices, the power conversion efficiencies (PCE) of champion devices using the LTPC-CE were increased from 14.99% for the MTPC-CE cell to 17.68%. In large-area devices, PCE improved from 12.24 to 15.01%. Transient photovoltage and photocurrent measurements confirmed the enhanced performance of the devices incorporating the LTP graphene-based carbon paste as the CE. Our findings highlight the high potential of low-temperature processed carbon electrodes for stable and efficient PSCs, offering a promising approach for the massive and affordable production of perovskite-based photovoltaics.

A facile, ultralow‐cost, and up‐scalable printable manufacturing process of flexible, multifunctional sensors that respond to more than one external stimulus could have a pivotal role in low‐cost wearables and portable systems for Industry 4.0. Herein, using a low capex, in‐house spray coating system, the fabrication of a low‐cost photodetector that is tuneable by mechanical strain exploiting the piezo‐phototronic nature of defect‐free 2D In 2 Se 3 nanosheets is reported. Moreover, force sensors that respond to different levels of applied force are spray‐coated by using In 2 Se 3 nanosheets. Regarding the photodetector, a nonmonotonic and asymmetric effect of strain on photocurrent response is shown exhibiting a local maximum at the 23°–32° compressive angle range and a slight hysteresis. Forward compressive bending leads to a photocurrent enhancement by 27% at 32° and reverse by 31% at 23°, while tensile strain leads to a current suppression by 8–10% at 23°–32° angle. The resulting force sensor repeatably demonstrates discrete piezoelectric voltages in the millivolt scale upon different mass loads, opening the path for force and tactile sensing applications. Applying industrially compatible materials for the underlying flexible substrate and electrodes, combined with spray coating, removes manufacturing complexities that engage costly and energy intensive fabrication.

Multifunctional Sensors In article 22300203, Konstantinos Rogdakis, Emmanuel Kymakis, and co-workers demonstrate the exploitability of defect-free In2Se3 nanosheets for dual use in photo-sensing and strain sensing applications by involving facile, low-capex fabrication and industrially available materials. The resulting strain-tuneable photosensors exhibit excellent ambient stability and good light sensitivity. Finally, the realisation of a weight sensor further adds prospects to employing In2Se3 as the functional material.

The lifetime of inverted PSCs is extended by employing for the first time the hydrophobic conjugated polymer PIDTTDQ. The optimized PIDTTDQ device shows an increased PCE due to the improved HTL/Perovskite interface while having enhanced moisture, light and thermal stability.

The high-power conversion efficiency of flexible perovskite photovoltaics (PPV) at low light environment and their low-cost manufacturing processes, render PPV superior to conventional rigid photovoltaics targeting indoor applications. However, various parameters related to materials, architecture, processing, and indoor characterization need to be optimized further toward improving indoor PPV (iPPV) efficiency, stability, and ecotoxicity. This work provides an overview of the recent progress, trends, and challenges in the field and suggests a holistic approach toward a viable design and integration of iPPVs into Internet of Things (IoT) platforms without any compromise on safety and cost effectiveness. The key impact of selecting proper materials and fabrication techniques, as well as optimizing the active area and architecture is described. Certain peculiarities of the indoor lighting conditions are discussed that can be addressed by proper simulation tools, including the understanding of the charge-transfer mechanism, the diversification of the lamp types, as well as identifying the requirements for the production, standardization, and installation of iPPVs associated with IoT devices. A multidimensional engineering approach that considers aspects of architecture, light technology, load specifications, materials, processing, safety and cost, is proposed as a path toward accelerating iPPV market uptake for households, businesses, wearables and Industry 4.0 applications.

A novel solution-processed, graphene-based material was synthesized by treating graphene oxide (GO) with 2,5,7-trinitro-9-oxo-fluorenone-4-carboxylic acid (TNF-COOH) moieties, via simple synthetic routes. The yielded molecule N-[(carbamoyl-GO)ethyl]-N′-[(carbamoyl)-(2,5,7-trinitro-9-oxo-fluorene)] (GO-TNF) was thoroughly characterized and it was shown that it presents favorable highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels to function as a bridge component between the polymeric donor poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl}) (PTB7) and the fullerene derivative acceptor [6,6]-phenyl-C71-butyric-acid-methylester (PC71BM). In this context, a GO-TNF based ink was prepared and directly incorporated within the binary photoactive layer, in different volume ratios (1%–3% ratio to the blend) for the effective realization of inverted ternary organic solar cells (OSCs) of the structure ITO/PFN/PTB7:GO-TNF:PC71BM/MoO3/Al. The addition of 2% v/v GO-TNF ink led to a champion power conversion efficiency (PCE) of 8.71% that was enhanced by ~13% as compared to the reference cell.

A conjugated, ladder-type multi-fused ring 4,7-dithienbenzothiadiazole:thiophene derivative, named as compound ‘T’, was for the first time incorporated, within the PTB7:PC71BM photoactive layer for inverted ternary organic solar cells (TOSCs) realization. The effective energy level offset caused by compound T between the polymeric donor and fullerene acceptor materials, as well as its resulting potential as electron cascade material contribute to an enhanced exciton dissociation, electron transfer facilitator and thus improved overall photovoltaic performance. The engineering optimization of the inverted TOSC, ITO/PFN/PTB7:Compound T(5% v/v):PC71BM/MoO3/Al, resulted in an overall power conversion efficiency (PCE) of 8.34%, with a short-circuit current density (Jsc) of 16.75 mA cm−2, open-circuit voltage (Voc) of 0.74 V and a fill factor (FF) of 68.1%, under AM1.5G illumination. This photovoltaic performance was improved by approximately 12% with respect to the control binary device.

Inverted perovskite solar cells (PSCs) have attracted much interest due to their improved operational stability in the past few years. However, despite the recent advances of their performance, they still suffer from low power conversion efficiencies with a reduced open-circuit voltage (V-oc), as compared to PSCs with a regular structure, due to the presence of defect states. In this work, a promising and more effective strategy than the typical post-treatment passivation method is demonstrated for the decrease of nonradiative recombination in quadruple-cation R(b)C(s)MAFA inverted PSCs, through the employment of phenethylammonium iodide in the anti-solvent deposition step during the perovskite formation. As a result, a V-oc value as high as 1.17 V is achieved, while control devices (where the typical chlorobenzene anti-solvent was used) exhibited a significantly lower V-oc of 1.09 V. Additionally, the devices exhibited high moisture stability by maintaining nearly 80% of their initial efficiency for over 500 h exposure in ambient conditions.

Hydroiodic acid (HI)-treated reduced graphene oxide (rGO) ink/conductive polymeric composites are considered as promising cold cathodes in terms of high geometrical aspect ratio and low field emission (FE) threshold devices. In this study, four simple, cost-effective, solution-processed approaches for rGO-based field effect emitters were developed, optimized, and compared; rGO layers were coated on (a) n+ doped Si substrate, (b) n+-Si/P3HT:rGO, (c) n+-Si/PCDTBT:rGO, and (d) n+-Si/PCDTBT:PC71BM:rGO composites, respectively. The fabricated emitters were optimized by tailoring the concentration ratios of their preparation and field emission characteristics. In a critical composite ratio, FE performance was remarkably improved compared to the pristine Si, as well as n+-Si/rGO field emitter. In this context, the impact of various materials, such as polymers, fullerene derivatives, as well as different solvents on rGO function reinforcement and consequently on FE performance upon rGO-based composites preparation was investigated. The field emitter consisted of n+-Si/PCDTBT:PC71BM(80%):rGO(20%)/rGO displayed a field enhancement factor of ~2850, with remarkable stability over 20 h and low turn-on field in 0.6 V/μm. High-efficiency graphene-based FE devices realization paves the way towards low-cost, large-scale electron sources development. Finally, the contribution of this hierarchical, composite film morphology was evaluated and discussed.

In the present study we focus on the optimization of NP concentration of ZnO used as an ETL for the fabrication of fully printed inverted OPVs by lab-scale Sheet-to-Sheet gravure technique. The inverted OPV architecture consistσ of the layer sequence: PET/ITO/ZnO/P3HT:PCBM/PEDOT:PSS/Ag. By diversifying ZnO nanoparticle concentration, we track the optimum concentration for better OPV efficiencies and try to correlate concentration to the electrical characteristics of the OPV and other ETL characteristics such as thickness, surface morphology and roughness, hydrophilicity etc. Further goal of this work is to achieve a cost-efficient scalability of flexible organic photovoltaics (OPVs), the optimization of the ZnO NPs and of the printing processes.

A novel approach for the fabrication of flexible organic photovoltaic (OPV) modules with an inverted architecture by gravure printing process is presented. The printing has been carried out using a sheet-to-sheet (S2S) lab scale proofer, while all the printing steps were performed in ambient conditions and optimized for each of the OPV layers. Commercially available Zinc Oxide (ZnO) ink was used as the electron transport (ETL) layer, poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) blend comprised the bulk heterojunction (BHJ) photoactive layer, poly-3,4-ethylenedioxy-thiophene:poly(styrenesulfonic-acid) (PEDOT:PSS) was used as the hole transport layer (HTL), and silver (Ag) nanoparticle (NP) ink was used as the top contact electrode. The four OPV layers have been successively printed on indium tin oxide (ITO) coated polyethylene terephthalate (PET) flexible substrate using the same printing parameters. The OPV modules have size of 45 cm2 with an active area of 8 cm2 composed of 8 interconnected cells and exhibited a maximum power conversion efficiency (PCE) of over 2%. The printing parameters were optimized by the contribution of extensive morphological characterization by scanning and transmission electron microscopy (SEM, TEM), as well as from Spectroscopic Ellipsometry (SE) for the determination of the printed layers thickness, optical properties and photoactive layer blend morphology. The above approach reveals the required printing parameters for large-scale manufacturing of flexible OPVs by a R2R process.

In this work, we describe a novel approach for the fabrication of flexible organic photovoltaic (OPV) modules with an inverted architecture by a versatile and scalable gravure printing process. The printing has been carried out using a sheet-to-sheet (S2S) lab scale proofer, while all the printing steps were performed in ambient conditions and were optimized for each of the OPV layers. Commercially available zinc oxide (ZnO) ink was used as the electron transport (ETL) layer, poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) blend comprised the bulk heterojunction (BHJ) photoactive layer, poly-3,4-ethylenedioxy-thiophene:poly(styrenesulfonic-acid) (PEDOT:PSS) was used as the hole transport layer (HTL), and silver (Ag) nanoparticle ink was used as the top contact electrode. The four OPV layers have been successively printed on indium tin oxide (ITO) coated polyethylene terephthalate (PET) flexible substrate using the same printing parameters, allowing the high production throughput in a roll-to-roll (R2R) printing process. The printed OPV modules have size of 45cm2 with an active area of 8cm2 composed of 8 interconnected cells and exhibited a maximum power conversion efficiency (PCE) of 2.22%. The printing parameters were optimized by the contribution from extensive morphological characterization carried out by scanning and transmission electron microscopy (SEM, TEM), as well as from Spectroscopic Ellipsometry (SE) for the determination of the printed layers thickness, optical properties and photoactive layer blend morphology. The above approach revealed the required printing parameters for the further optimization of the layer interface, morphology, thickness and substrate properties in order to implement the above methodology for large-scale manufacturing of flexible OPVs by a R2R process.

Interfacing organic electrochemical transistors (OECTs) with biological systems holds considerable promise for building-sensitive biosensors and diagnostic tools. We present a simple model that describes the performance of biosensors in which an OECT is integrated with a biological barrier layer. Using experimentally derived parameters we explore the limits of sensitivity and find that it is dependent on the resistance of the barrier layer. This work provides guidelines on how to optimize biosensors in which OECTs transduce changes in the impedance of biological layers, including lipid bilayer membranes and confluent cell layers.