The defects present in solution-processed perovskite light absorbing materials are responsible for deteriorating the performance and stability of perovskite solar cells. Therefore, suppressing the defect formation and passivating the pre-existing defects in perovskite materials are of paramount importance in pushing the efficiency of perovskite solar cells (PSCs) toward the theoretical limit and ensuring the long-term stability of PSCs. In this work, we report an efficient defect passivation route using a bidentate small organic molecule, pyrazine, which is capable of making either a monodentate or a bridging bidentate bond with under-coordinated Pb²⁺ ions mainly present in the surface and grain boundaries of perovskite films. The various analyses for the defect density and charge carrier lifetime of perovskite light absorbing layers demonstrated that pyrazine effectively passivated defects existing on the surface and grain boundaries of the perovskite films without affecting the morphology and crystallinity via a simple post-treatment procedure. As a result, the best untreated device obtained a power conversion efficiency of 19.14%, while an efficiency of 20.58% was achieved when pyrazine treated.

Recently, metal halide perovskite-based top cells have shown significant potential for use in inexpensive and high-performance tandem solar cells. In state-of-the-art p-i-n perovskite/Si tandem devices, atomic-layer-deposited SnO₂ has been widely used as a buffer layer in the top cells because it enables conformal, pinhole-free, and highly transparent buffer layer formation. In this work, the effects of various electrical properties of SnO₂ and C60 layers on the carrier transport characteristics and the performance of the final devices were investigated using a numerical simulation method, which was established based on real experimental data to increase the validity of the model. It was found that the band alignment at the SnO₂/C60 interface does, indeed, have a significant impact on the electron transport. In addition, as a general design rule, it was suggested that at first, the conduction band offset (CBO) between C60 and SnO₂ should be chosen so as not to be too negative. However, even in a case in which this CBO condition is not met, we would still have the means to improve the electron transport characteristics by increasing the doping density of at least one of the two layers of C60 and/or SnO₂, which would enhance the built-in potential across the perovskite layer and the electron extraction at the C60/SnO₂ interface.

The addition of small amounts of Ag to Cu(In,Ga)Se₂ (CIGS) absorbers improves the device performance of CIGS solar cells by changing the film microstructure, alkali distribution, and electrostatic conditions of CIGS.

A simple, air processable, DMF molecular ink-based process is presented through which it was able to achieve a new certified record efficiency of 14.4% for the low-gap CuIn(S,Se)₂device.