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Highlights: [•] An efficient inverted polymer solar cell is demonstrated. [•] The electron collection layer consists of a small molecular layer of Cs2CO3:Alq3. [•] Efficient electron extraction is achieved due to favorable energy level alignment. [•] The Cs2CO3:Alq3 layer can act as an optical spacer to modulate the incident light. [ABSTRACT FROM AUTHOR]

Abstract While metal halide hybrid perovskite solar cells (PeSCs) are remarkably efficient, the rapid and undesirable degradation limit their practical applications for renewable energy sources. Herein, the evolution of perovskite decomposition under white light illumination has been investigated under the ultrahigh vacuum conditions, which can effectively rule out the influence of other factors such as oxygen or moisture. The chemical composition, electronic structure, surface morphology, and crystal structure of CH 3 NH 3 PbI 3 perovskite films have been systematically characterized by X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS), scanning electron microscopy, and X-ray diffraction techniques. The surface roughening with cracks and defects occurs in CH 3 NH 3 PbI 3 perovskite films after a short-time white-light illumination in ultrahigh vacuum. In situ compositional analysis reveals the decomposition of the perovskite films with the appearance of metallic Pb feature, which is accompanied with the energy level shift towards higher binding energy during the illumination process. However, the decomposition rate is decreased and becomes saturated after exposed to light illumination for 24 h. These findings provide a direct evidence that CH 3 NH 3 PbI 3 perovskite is photosensitive, and a light-induced degradation mechanism is proposed. Graphical abstract Image 1 Highlights • The perovskite decomposition under white light illumination is explored under ultrahigh vacuum conditions. • In-situ compositional analysis reveals the perovskite decomposition with the appearance of metallic Pb. • A light-induced degradation mechanism is proposed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Efficient polymer solar cell is demonstrated with a nanostructured scattering rear electrode. [•] Enhanced light harvesting is realized through efficient backscattering-induced light trapping. [•] An enhanced power conversion efficiency of 7.21% is obtained. [ABSTRACT FROM AUTHOR]

Abstract: An efficient inverted polymer solar cell is enabled by incorporating an n-type doped wide-gap organic electron transporting layer (ETL) between the indium tin oxide cathode and the photoactive layer for electron extraction. The ETL is formed by a thermal-deposited cesium carbonate-doped 4,7-diphenyl-1,10-phenanthroline (Cs2CO3:BPhen) layer. The cell response parameters critically depended on the doping concentration and film thickness of the Cs2CO3:BPhen ETL. Inverted polymer solar cell with an optimized Cs2CO3:BPhen ETL exhibits a power conversion efficiency of 4.12% as compared to 1.34% for the device with a pristine BPhen ETL. The enhanced performance in the inverted device is associated with the favorable energy level alignment between Cs2CO3:BPhen and the electron-acceptor material, as well as increased conductivity in the doped organic ETL for electron extraction. The method reported here provides a facile approach to optimize the performance of inverted polymer solar cells in terms of easy control of film morphology, chemical composition, conductivity at low processing temperature, as well as compatibility with fabrication on flexible substrates. [Copyright &y& Elsevier]

Abstract: An efficient inverted polymer solar cell (PSC) is reported by employing an atomic layer deposited (ALD) cadmium sulfide (CdS) film between the indium tin oxide (ITO) cathode and the photoactive layer as the electron collection layer (ECL), on which a active layer is composed of a blended poly(3-hexylthiophene) and [6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) bulk heterojunction. As determined by photoelectron spectroscopy, the sulfur vacancy induces an n-type semiconducting property in the ALD-grown CdS films, and suitable energy level alignment at the ITO/CdS/PCBM interface is favorable to electron extraction through CdS to the ITO electrode. With the optimized CdS film thickness, the power conversion efficiency increases to 3.33%, with short-circuit current of 8.94mA/cm2, open-circuit voltage of 0.61V, and fill factor of 61.1% under AM1.5G 100mW/cm2 irradiation. [Copyright &y& Elsevier]