Additive engineering has become a critical strategy for optimizing the morphology and performance of bulk heterojunction (BHJ) organic solar cells (OSCs), while volatile solid additives have been widely employed to control nanoscale phase separation during film formation. Concerns regarding reproducibility, residual solvent effects, and long-term stability have stimulated increasing interest in non-volatile solid additives. In recent years, solid additive engineering has emerged as a promising approach for modulating molecular packing, regulating phase separation, enhancing charge transport, and improving device stability. However, a systematic analysis of its material design principles and performance impact remains limited. This review summarizes recent progress in solid additive engineering for OSCs, categorizing reported additives into non-volatile, volatile and nanomaterials. The effects of these additives on key photovoltaic parameters, including open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and power conversion efficiency (PCE), are comparatively analyzed based on the reported data. Particular emphasis is placed on morphology and structural performance relationships and stability enhancement mechanisms. Finally, current challenges, including the lack of universal molecular design rules and limited mechanistic understanding of additive host interactions, are discussed, and future research directions are proposed. This review aims to provide a comprehensive perspective on the material-level role of solid additives and to guide the rational design of next-generation high-performance and stable organic solar cells.

The optical properties, electronic structure and morphology of thin films of the polymer donor PTB7-Th blended with either the fullerene acceptor PC70BM or the non-fullerene acceptor ZY-4Cl were systematically investigated to evaluate their annealing-induced evolution. Thin films were characterized using UV–Vis–NIR absorption spectroscopy, spectroscopic ellipsometry, ATR-FTIR spectroscopy, atomic force microscopy (AFM), and nano-IR analysis. In situ stepwise thermal annealing revealed distinct changes in absorption edge parameters, indicating thermally induced modifications in the electronic structure of the blend films. Ellipsometric analysis showed that elevated temperatures significantly affect the refractive index and extinction coefficient spectra. AFM measurements demonstrated markedly different surface morphology evolution for the two blend systems, with pronounced needle-shaped crystallites formation observed in PTB7-Th:ZY-4Cl films after annealing at 100 °C. Nano-IR characterization identified these crystallites as predominantly PTB7-Th, indicating phase separation driven by thermal treatment. The combined optical and structural results reveal distinct annealing-induced changes in the blend. Finally, BHJ solar cells, based on PTB7-Th:PC70BM and PTB7-Th:ZY-4Cl active layers, were fabricated, and their photovoltaic response was demonstrated.

One of the key parameters characterizing the microstructure of a layer is its degree of order. It can be determined from optical studies or X-ray diffraction. However, both of these methods applied to the same layer may give different results because, for example, aggregates may contribute to the amorphous background in XRD studies, while in optical studies, they may already show order. Because we are usually interested in the optical and/or electrical properties of the layers, which in turn are closely related to their dielectric properties, determining the optical order of the layers is particularly important. In this work, the microstructure, optical properties and electrical conductivity of poly(3-hexyl)thiophene layers were investigated, and a model describing the electrical conductivity of these layers was proposed. The model is based on the generalized theory of the effective medium and uses the equation from the percolation theory of electrical conductivity for the effective medium of a mixture of two materials. The results indicate a key role of the aggregate size and limited conductivity of charge carriers, mainly due to structural imperfections that manifest themselves as an increase in the number of localized states visible in the subgap absorption near the optical absorption edge. The critical value of the order parameter and the corresponding values of the Urbach energy, excitonic linewidth and band gap energy are determined.

Fossil fuel reserves are rapidly depleting, while global energy demand continues to rise due to urbanization. Therefore, renewable energy sources are essential to meet future energy needs. Organic solar cells (OSCs) have emerged as promising next-generation photovoltaic technologies owing to their flexibility, lightweight nature, and compatibility with low-cost solution processing. However, achieving commercially viable efficiencies requires strategic optimization of both device architecture and electronic parameters. In this study, a comprehensive simulation based investigation was conducted using the SCAPS-1D to analyze the impact of key physical and electronic factors on OSC performance. The device was simulated using an inverted configuration such as FTO/PFN-Br/PBDB-T-2F:BTP-4F/CFTS/Pt, where FTO serves as the front contact, PFN-Br act as the electron transport layer (ETL), PBDB-T-2F:BTP-4F as the bulk heterojunction (BHJ) active layer, Cu ₂ FeSnS ₄ (CFTS) serves as the hole transport layer (HTL), while platinum is employed as the back contact. Parameters such as the active layer thickness, defect density, band gap tuning, electron affinity, charge transport layer doping, and back contact work function were optimized. The resulting device achieved an open circuit voltage (Voc) of 1.057 V, a short circuit current density (Jsc) of 21.833 mA cm ⁻² , a fill factor (FF) of 62.28%, and a power conversion efficiency (PCE) of 14.38%. The key novelty of this work lies in the employing CFTS as a non-toxic, earth-abundant HTL, which offers favorable energy level alignment with the PBDB-T-2F:BTP-4F active layer, enabling efficient hole extraction and reducing interfacial energy barriers. These findings present a sustainable and efficient design strategy for high-performance inverted OSCs, contributing to the advancement of scalable renewable energy technologies.

Organic photovoltaics (OPVs) based on non-fullerene acceptors (NFAs) are rapidly advancing as lightweight, flexible, and low-cost solar technologies, with power conversion efficiencies approaching 20%. To ensure that environmental sustainability progresses symmetrically alongside performance improvements, it is essential to quantify the environmental footprint of these emerging technologies, particularly during early development stages when material and process choices remain adaptable. This study presents a cradle-to-gate life cycle assessment (LCA) of PTB7-Th:ZY-4Cl solar cells, aiming to identify asymmetries in environmental impact distribution and guide eco-efficient optimization strategies. Using laboratory-scale fabrication data, global warming potential (GWP), cumulative energy demand (CED), acidification (AP), eutrophication (EP), and fossil fuel depletion (FFD) were evaluated via the TRACI methodology. Results reveal that electricity consumption in thermomechanical operations (ultrasonic cleaning, spin coating, annealing, and stirring) disproportionately dominates most impact categories, while chemical inputs such as PEDOT:PSS, PTB7-Th:ZY-4Cl precursors, and solvents contribute significantly to fossil fuel depletion. Substituting grid electricity with renewable sources (hydro, wind, PV) markedly reduces GWP, and solvent recovery or replacement with greener alternatives offers further gains. Although extrapolation to a 1 m² pilot-scale module reveals impacts higher than established PV technologies, prospective scenarios with realistic efficiencies (10%) and lifetimes (10–20 years) suggest values of ~150–500 g CO₂-eq/kWh—comparable to fullerene OPVs and approaching perovskite and thin-film benchmarks. These findings underscore the value of early-stage LCA in identifying asymmetrical hotspots, informing material and process optimization, and supporting the sustainable scale-up of next-generation OPVs.