Dielectric constant (ε) is an important parameter affecting the power conversion efficiency of organic solar cells (OSC). Increasing ε of bulk heterojunctions in general can benefit the performance of OSCs, as an increased ε will reduce the influence of Coulomb interaction between weakly bound electron‐hole pairs on charge‐transfer states or bimolecular recombination involving mobile carriers to reduce geminate and nongeminate losses. In this review, we overview the current understandings on dielectric constant and its impacts on exciton dissociation and voltage losses in OSCs and summarize recent efforts attempting to modify the dielectric properties of OSC materials through synthetic approaches. We further discuss the commonly adopted techniques for determining the parameter of ε with stressing the testing conditions that may affect the accuracy of results. At last, we suggest that novel experimental methods to improve the dielectric constant and resultant physical processes in OSCs will be appreciated, which helps enrich the existing strategy reservoir toward enhancement of photovoltaic efficiencies.

Quasi-two-dimensional (2D) perovskites are highly promising light-harvesting materials for commercialization of perovskite solar cells (PSCs) owing to the excellent materials stability. However, the coexistence of multiple n-value species in 2D perovskites often causes increased complexities in crystallization that can negatively affect the eventual photovoltaic performance. Herein, we present a binary solution based strategy via introducing nontoxic and widely accessible CH 3 COOH (HAc) as a co-solvent for preparing high-quality 2D perovskite films. Based on a 2D perovskite model system, (AA) 2 MA 4 Pb 5 I 16 (n = 5), we show that the prenucleation and grain growth kinetics are appreciably modified with HAc, which benefits from the strong electrondonating ability of HAc with the key component of PbI 2 , leading to formation of favorable cluster aggregates and resultant modulation of crystal growth. With the HAc-based method, the devices yield a boosted photovoltaic efficiency of 18.55% with an impressive photovoltage of 1.26 V. The champion cells exhibit a supreme thermal stability, showing <3% efficiency degradation under continuous thermal aging for 800 h.

Spur gears are widely used transmission components. In the traditional design process, the noninvolute part of the tooth profile curve is difficult to describe with mathematical equations. is article puts forward a new parametric modeling method, which can describe the modified involute part of spur gears and parameterize and optimize the transition part of the involute curve of the spur gear. And this model of the spur gear can be created by parameters which is input in Scilab software and the spur gear graphic can be completed correspondingly. e experiments show that this modeling method can more quickly produce the standard spur or modified spur gear, and it also improves the efficiency and accuracy of spur gear modeling.