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Sputtering with copper indium gallium selenide (CIGS) ceramic targets could produce smooth CIGS thin films that are preferred for preparing two-terminal tandem devices. However, grain sizes prepared in this way are small and device efficiency was low. To increase the grain size, in this report, an Ag layer was pre-sputtered beneath CIGS. The Ag doping layer increased the grain size and improved the crystalline alignment. Consequently, the Ag-doped films exhibited improved charge mobility. From X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy characterizations, we obtained an optimized Ag thickness of 15 nm. Short-circuit current density (JSC), open-circuit voltage (VOC), and fill factor (FF) were all improved after doping with 15-nm Ag. Increasing the annealing temperature from 550 °C to 575 °C, the grains was enlarged further, with the power conversion efficiency (PCE) increasing to 14.33% and VOC to 545 mV. Upon the smooth CIGS film, a thin conformal perovskite layer was fabricated without polishing. This work demonstrates a simple way to fabricate smooth and highly-crystalline CIGS films that can be used for tandem solar cells.

Herein, 1,6-Diaminohexane Dihydrochloride (1,6-DD) is introduced into perovskite precursors to fabricate the inverted planar perovskite solar cells. By regulating the concentration of 1,6-DD additive, the average power conversion efficiency (PCE) of perovskite solar cells is enhanced by 20%. The champion device achieves a relatively high PCE of 17% and an excellent fill factor of 80.1%. The PCE of the large-area (1 cm2) device also reaches to 13.68%. After exposure to the air for 16 days, the device with 1,6-DD additive still retains above 90% of the initial efficiency, exhibiting good stability. We demonstrate that a small amount of 1,6-DD affects the crystallization dynamic, yielding ideal perovskite film with enhanced crystallinity and enlarged grain size. The two terminal -NH3+ groups passivates the vacancy defects at the perovskite crystal surface, suppressing charge recombination and facilitating charge transportation effectively. Meanwhile, adjacent crystal surfaces are linked through the hexane alkyl chain of 1,6-DD molecule, which enhances the interaction between perovskite grains and anchors the microstructure of perovskite to some degree. Hydrophobic hexane alkyl chains also increase the moisture resistance of perovskite film. Thus, an easy and effective way is provided for fabricating efficient and stable perovskite solar cells.

Herein, a low-melting point tin-bismuth (SnBi) alloy film combined with a silver layer was introduced to fabricate the inverted planar perovskite solar cells. SnBi alloy was prepared by high temperature melting method and was characterized by metallurgical microscope, XRD, SEM, DTA, XPS methods. The influence of silver thickness on the performance of perovskite solar cells was studied. The optimized perovskite solar cells based on 20 nm Ag and 80 nm SnBi show a power conversion efficiency of 13.52%, involving a 19.6% increase compared to the control device. The double-layer electrode can not only reduce the charge transfer resistance, increase the extraction efficiency of the charge, improve the photovoltaic performance of the device, but also improve the stability of the device in the environment.