As a promising strategy for enhancing light utilization, constructing cell with tandem structure exhibits great potential in achieving high efficiency, which encourages the field of organic solar cells. Here, we develop an advanced interconnecting layer for tandem organic solar cell, which is composed of electron beam evaporated TiO x and PEDOT:PSS. By using electron beam evaporation, a sharp, smooth, and dense TiO x /PEDOT:PSS interface is obtained. By exquisite controlling the O 2 flux during evaporation, efficient electron extraction and low Schottky barrier are obtained in PBDB-TF:GS-ISO/TiO 1.76 and TiO 1.76 /PEDOT:PSS, which guarantee the charge recombination between two subcells. The tandem cell with interconnecting layer of TiO 1.76 /PEDOT:PSS shows 20.27% efficiency, which is certified as 20.0% by National Institute of Metrology, China. Therefore, our result marks the arrival of 20% era in the field of organic solar cells.

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Ternary polymer solar cells are fabricated based on one donor PBDB-T and two acceptors (a methyl-modified small-molecular acceptor (IT-M) and a bis-adduct of Bis[70]PCBM). A high power conversion efficiency of 12.2% can be achieved. The photovoltaic performance of the ternary polymer solar cells is not sensitive to the composition of the blend.

This research sheds light on the morphology of state-of-the-art nonfullerene organic solar cells (OSCs) from the perspective of thermodynamics and formation kinetics. We find that OSC morphology needs to be kinetically quenched for achieving optimal performance if the molecular interaction of constituent materials is too repulsive. The results provide useful guidelines for improving fabrication yield, reliability, and stability of a large class of high-performance OSCs. (H.A.) HIGHLIGHTS Quench depth of a high-efficiency nonfullerene system was determined Quench depth, formation kinetics, and percolation threshold were correlated Morphology needs to be kinetically quenched for deep quench depth systems Ye et al., Joule 3,[443][444][445][446][447][448][449][450][451][452][453][454][455][456][457][458] February 20, SUMMARYThe general lack of knowing the quench depth and the convolution with key kinetic factors has confounded deeper understanding of the respective importance of these factors in the morphology development of organic solar cells. Here, we determine the quench depth of a high-efficiency system and delineate the need to kinetically quench the mixed domains to a composition close to the percolation threshold. Importantly, the ability to achieve such a quench is very sensitive to structural parameters in polymer solar cells (PSCs) of the polymer PBDB-TF. Only the highest-molecular-weight polymer is able of earlier liquidsolid transition to ''lock in'' a high-performing PSC morphology with a composition above the miscibility limit and with an efficiency of over 13%. Systems with deep quench depths are therefore sensitive to molecular weight and the kinetic factors of the casting, likely impacting fabrication yield and reliability. They also need to be vitrified for stable performance.

Despite more potential in realizing higher photovoltaic performance, the highest power conversion efficiency (PCE) of tandem organic photovoltaic (OPV) cells still lags behind that of state‐of‐the‐art single‐junction cells. In this work, highly efficient double‐junction tandem OPV cells are fabricated by optimizing the photoactive layers with low voltage losses and developing an effective method to tune optical field distribution. The tandem OPV cells studied are structured as indium tin oxide (ITO)/ZnO/bottom photoactive layer/interconnecting layer (ICL)/top photoactive layer/MoOx/Ag, where the bottom and top photoactive layers are based on blends of PBDB‐TF:ITCC and PBDB‐TF:BTP‐eC11, respectively, and ICL refers to interconnecting layer structured as MoOx/Ag/ZnO:PFN‐Br. As these results indicate that there is not much room for optimizing the bottom photoactive layer, more effort is put into fine‐tuning the top photoactive layer. By rationally modulating the composition and thickness of PBDB‐TF:BTP‐eC11 blend films, the 300 nm‐thick PBDB‐TF:BTP‐eC11 film with 1:2 D/A ratio is found to be an ideal photoactive layer for the top sub‐cell in terms of photovoltaic characteristics and light distribution control. For the optimized tandem cell, a PCE of 19.64% is realized, which is the highest result in the OPV field and certified as 19.50% by the National Institute of Metrology.

The power conversion efficiencies (PCEs) of state-of-the-art organic solar cells (OSCs) have increased to over 13%. However, the most commonly used solvents for making the solutions of photoactive materials and the coating methods used in laboratories are not adaptable for future practical production. Therefore, taking a solution-coating method with environmentally friendly processing solvents into consideration is critical for the practical utilization of OSC technology. In this study, a highly efficient PBTA-TF:IT-M-based device processed with environmentally friendly solvents, tetrahydrofuran/isopropyl alcohol (THF/IPA) and o-xylene/1-phenylnaphthalene, is fabricated; a high PCE of 13.1% can be achieved by adopting the spin-coating method, which is the top result for OSCs. More importantly, a blade-coated non-fullerene OSC processed with THF/IPA is demonstrated for the first time to obtain a promising PCE of 11.7%; even for the THF/IPA-processed large-area device (1.0 cm ) made by blade-coating, a PCE of 10.6% can still be maintained. These results are critical for the large-scale production of highly efficient OSCs in future studies.

Perovskite and chalcogenide quantum dots (QDs) are important nano semiconductors. It has been a challenge to synthesize heterostructural QDs combining perovskite and chalcogenide with tailorable photoelectronic properties. In this report, heterostructural CsPbX3-PbS (X = Cl, Br, I) QDs were successfully synthesized via a room temperature in situ transformation route. The CsPbX3-PbS QDs show a tunable dual emission feature with the visible and near-infrared (NIR) photoluminescence (PL) corresponding to CsPbX3 and PbS, respectively. Typically, the formation and evolution of the heterostructural CsPbBr3–PbS QDs with reaction time was investigated. Femtosecond transient absorption spectroscopy (TAS) was applied to illuminate the exciton dynamics in CsPbBr3–PbS QDs. The mild synthetic method and TAS proved perovskite to PbS energy transfer may pave the way toward highly efficient QD photovoltaic and optoelectronic devices.