Polymer Solar Cells with 90% External Quantum Efficiency Featuring an Ideal Light‐ and Charge‐Manipulation Layer

Rapid progress in the power conversion efficiency (PCE) of polymer solar cells (PSEs) is beneficial from the factors that match the irradiated solar spectrum, maximize incident light absorption, and reduce photogenerated charge recombination. To optimize the device efficiency, a nanopatterned ZnO:Al₂O₃ composite film is presented as an efficient light‐ and charge‐manipulation layer (LCML). The Al₂O₃ shells on the ZnO nanoparticles offer the passivation effect that allows optimal electron collection by suppressing charge‐recombination loss. Both the increased refractive index and the patterned deterministic aperiodic nanostructure in the ZnO:Al₂O₃ LCML cause broadband light harvesting. Highly efficient single‐junction PSCs for different binary blends are obtained with a peak external quantum efficiency of up to 90%, showing certified PCEs of 9.69% and 13.03% for a fullerene blend of PTB7:PC₇₁BM and a nonfullerene blend, FTAZ:IDIC, respectively. Because of the substantial increase in efficiency, this method unlocks the full potential of the ZnO:Al₂O₃ LCML toward future photovoltaic applications.     

Toward Efficient Polymer Solar Cells Processed by a Solution‐Processed Layer‐By‐Layer Approach

The solution‐processed layer‐by‐layer (LBL) method has potential to achieve high‐performance polymer solar cells (PSCs) due to its advantage of enriching donors near the anode and acceptors near the cathode. However, power conversion efficiencies (PCEs) of the LBL‐PSCs are still significantly lower than those of conventional one‐step‐processed PSCs (OS‐PSCs). A method to solve the critical problems in LBL‐PSCs is reported here. By employing a specific mixed solvent (o‐dichlorobenzene [o‐DCB]/tetrahydrofuran) to spin‐coat the small‐molecular acceptor IT‐4F onto a layer of the newly designed polymer donor (PBDB‐TFS1), appropriate interdiffusion between the PBDB‐TFS1 and the IT‐4F can critically be controlled, and then an ideal phase separation of the active layer and large donor/acceptor interface area can be realized with a certain amount of o‐DCB. The PSCs based on the LBL method exhibit PCEs as high as 13.0%, higher than that of the counterpart (11.8%) made by the conventional OS solution method. This preliminary work reveals that the LBL method is a promising approach to the promotion of the photovoltaic performance of polymer solar cells.     

Seed‐Assisted Growth for Low‐Temperature‐Processed All‐Inorganic CsPbIBr2 Solar Cells with Efficiency over 10%

All‐inorganic CsPbIBr₂ perovskite has recently received growing attention due to its balanced band gap and excellent environmental stability. However, the requirement of high‐temperature processing limits its application in flexible devices. Herein, a low‐temperature seed‐assisted growth (SAG) method for high‐quality CsPbIBr₂ perovskite films through reducing the crystallization temperature by introducing methylammonium halides (MAX, X = I, Br, Cl) is demonstrated. The mechanism is attributed to MA cation based perovskite seeds, which act as nuclei lowering the formation energy of CsPbIBr₂ during the annealing treatment. It is found that methylammonium bromide treated perovskite (Pvsk‐Br) film fabricated at low temperature (150 °C) shows micrometer‐sized grains and superior charge dynamic properties, delivering a device with an efficiency of 10.47%. Furthermore, an efficiency of 11.1% is achieved for a device based on high‐temperature (250 °C) processed Pvsk‐Br film via the SAG method, which presents the highest reported efficiency for inorganic CsPbIBr₂ solar cells thus far.     

Air‐Processed,Stable Organic Solar Cells with High Power Conversion Efficiency of 7.41%

High efficiency, excellent stability, and air processability are all important factors to consider in endeavoring to push forward the real‐world application of organic solar cells. Herein, an air‐processed inverted photovoltaic device built upon a low‐bandgap, air‐stable, phenanthridinone‐based ter‐polymer (C₁₅₀H₂₁₈N₆O₆S₄)_n (PDPPPTD) and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) without involving any additive engineering processes yields a high efficiency of 6.34%. The PDPPPTD/PC₆₁BM devices also exhibit superior thermal stability and photo‐stability as well as long‐term stability in ambient atmosphere without any device encapsulation, which show less performance decay as compared to most of the reported organic solar cells. In view of their great potential, solvent additive engineering via adding p‐anisaldehyde (AA) is attempted, leading to a further improved efficiency of 7.41%, one of the highest efficiencies for all air‐processed and stable organic photovoltaic devices. Moreover, the device stability under different ambient conditions is also further improved with the AA additive engineering. Various characterizations are conducted to probe the structural, morphology, and chemical information in order to correlate the structure with photovoltaic performance. This work paves a way for developing a new generation of air‐processable organic solar cells for possible commercial application.