José-Luis Maldonado

In the present study, silver sulfide nanoparticles (Ag ₂ S NPs) were synthesized in an aqueous medium under a nitrogen-controlled atmosphere. Nanoparticles exhibited an average size of 35 ± 2 nm, which were embedded at 0.5, 2 and 4 wt.% into PEDOT:PSS hole transport layer of organic solar cells (OSCs) based on PM6:Y7. Devices with the 0.5 wt.% of Ag ₂ S NPs relative to the PeEDOT:PSS solid content showed the best photovoltaic (PV) performance. OSCs fabrication and testing were carried out under room atmospheric conditions. Field’s Metal, a eutectic alloy of bismuth, indium, and tin (Bi 32.5%, In 51%, and Sn 16.5%) with a melting point of 62 °C, as top electrode, was deposited using the evaporation-free drop-casting technique. Reference/control (0 wt.% of Ag ₂ S NPs ) and plasmonic devices were fabricated simultaneously, achieving an average power conversion efficiency ( PCE ) of 9.30% (9.61% the best) and 10.04% (10.41% the best), respectively, at the doping level of 0.5 wt.% of Ag ₂ S NPs ; it means an increase of around 8% in PCE parameter. A 1123 h stability study, conducted according to the ISOS-D1 (shelf storage) protocol, further confirmed that the PV stability of plasmonic devices remained unaffected by the addition of NPs. The plasmonic OSCs PV performance improvement was validated through devices simulation, using the COMSOL Multiphysics software.

Organic solar cells (OSC) based on the donor polymer D18-Cl and the non-fullerene acceptor BTP-eC9 were fabricated using bulk heterojunction (BHJ) and layer-by-layer (LbL) architectures to evaluate their performance under fully ambient and scalable processing conditions. Devices were produced using identical solution formulations and a vacuum-free glass/ITO/PEDOT:PSS/active layer/PFN/metal stack. Whereas BHJ devices delivered an average PCE of 11.66 ± 0.21% (PCEmax = 11.87%), the LbL devices achieved a higher average PCE of 12.36 ± 0.17% (PCEmax = 12.53%), together with an increased J _SC (23.74 ± 0.49 versus 22.76 ± 0.63 mA cm ⁻² , respectively). EQE measurements confirmed stronger photo-response in the red/NIR region for LbL (up to 89%) compared to BHJ (83%). The LbL architecture showed lower series resistance and higher shunt resistance consistent with the photoluminescence (PL) quenching and electro-chemical impedance spectroscopy (EIS) measurements, which further confirmed enhanced interfacial charge transfer and lower charge-transfer resistance in LbL devices, while light-intensity dependence demonstrated reduced bimolecular and trap-assisted recombination than its BHJ counterpart.

This study presents a systematic analysis of the impact of polymer hole transport layers (HTLs) in inverted MAPbI₃ perovskite solar cells (PSCs). Devices were fully fabricated under regular atmospheric conditions (≈40% humidity) and low temperature (100 °C) by using Field's Metal (FM) as an alternative top electrode. The widely known π-conjugated polymers P3HT, PTB7-Th, PBDB-T, and MEH-PPV were used as HTLs, and all of them show suitable energy alignment to MAPbI₃, offering good moisture stability, solution processability, low cost, and attractiveness for large area and flexible PSCs. Morphological and structural characterization of MAPbI₃ via AFM, SEM, and XRD revealed consistent crystallinity, with MEH-PPV promoting a slightly larger grain size and surface modification. Current density-voltage (J-V) characteristics showed that MEH-PPV-based PSCs achieved an enhanced open-circuit voltage (V_oc ≈1.07 V) and fill factor (FF ≈75%), along with reduced hysteresis, while impedance spectroscopy (IS) confirmed enhanced charge extraction and lower ohmic losses. Simulations of external quantum efficiency (EQE) revealed that MEH-PPV reduces front-interface optical losses by ≈32% and charge recombination losses at the front and rear MAPbI₃ interfaces by ≈33% and ≈75%, respectively, in comparison to P3HT.

Organic solar cells (OSCs) are emerging as a viable alternative, and complementary niche of applications, to the conventional silicon-based photovoltaics due to their unique attributes, including flexibility, lightweight, semitransparency, and ease of processing. Recent breakthroughs in non-fullerene acceptors and advanced polymer donors have led to power conversion efficiencies exceeding 20%, closing the gap with traditional technologies. These advancements are driven by innovations in material design and engineering, enhanced understanding of device morphology, and improvements in fabrication architectures, as well as state-of-the-art characterization techniques. Despite these achievements, significant challenges remain, such as improving long-term device stability under environmental stress, upscaling OSCs from lab-scale devices to large-area modules through printing technologies, and achieving cost-effective scalability for mass production. This review also highlights OSCs’ transformative potential in niche applications such as semi-transparent photovoltaic windows, flexible/wearable electronics, and agricultural systems, paving the way for alternative sustainable and multifunctional energy solutions.

OSCs, all fabricated and tested under regular atmosphere. Interchain and intermolecular distance of PM6, Y7 and PM6:Y7 blend by scanning tunneling microscopy (STM).