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Postdeposition treatments (PDTs) are common technological approaches to achieve high-efficiency chalcogenide solar cells. For SnS, a promising solar cell material, most PDT strategies to control the SnS properties are overwhelmingly based on an annealing in sulfur-containing ambient atmosphere that is described by condensed-state reactions and vapor-phase transport. In this work, a systematic study of the impact of PDTs in a N2 atmosphere, ampules at temperatures between 400 and 600 °C, and a SnCl2 treatment at 250–500 °C on the properties of SnS films and SnS/CdS solar cells prepared by close-spaced sublimation is reported. The ampule and N2 annealing conditions do not affect the grain size of the SnS layers but significantly impact the concentration of intrinsic point defects, carrier density, and mobility. Annealing at 500–600 °C strongly enhances the hole concentration and decreases the carrier mobility, having detrimental impacts on the device performance. SnCl2 treatment promotes grain growth, sintering, and doping by mass transport through the melted phase; it adjusts the hole density and improves the carrier mobility in the SnS layers. SnS/CdS solar cells with an efficiency of 2.8% are achieved in the SnCl2 treatment step, opening new possibilities to further improve the performance of SnS-based devices.

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Fluorene-based hole transport materials (HTMs) with terminating thiophene units are explored, for the first time, for antimony sulfide (Sb 2 S 3 ) solar cells. These HTMs possess largely simplified synthesis processes and high yields compared to the conventional expensive hole conductors making them reasonably economical. The thiophene unit-linked HTMs have been successfully demonstrated in ultrasonic spray-deposited Sb 2 S 3 solar cells resulting in efficiencies in the range of 4.7−4.9% with an average visible transmittance (AVT) of 30−33% (400−800 nm) for the cell stack without metal contact, while the cells fabricated using conventional P3HT have yielded an efficiency of 4.7% with an AVT of 26%. The study puts forward cost-effective and transparent HTMs that avoid a post-coating activation at elevated temperatures like P3HT, devoid of parasitic absorption losses in the visible region and are demonstrated to be well aligned for the band edges of Sb 2 S 3 thereby ascertaining their suitability for Sb 2 S 3 solar cells and are potential candidates for semitransparent applications.

Zinc oxyselenideZn(O,Se)could become a novel buffer layer in solar cells and a functional layer in different optoelectronic devices. In this study, we systematically investigated the influence of the deposition temperature ranging from room temperature (RT) to 650 °C on the structural and optoelectronic properties of Zn(O,Se) layers grown on photovoltaic (PV) glass substrates by one-step pulsed laser deposition in a high vacuum. All layers were characterized using energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray diffractometry (XRD), UV−vis spectroscopy, and the Hall and van der Pauw technique. We demonstrated that polycrystalline, uniform, and electrically conductive Zn(O,Se) layers were grown at the substrate temperatures of 500−650 °C, while those layers grown at temperatures below 500 °C were characterized as amorphous and exhibiting a semi-insulating behavior. According to the XRD data, single-phase layers consisting of a ternary Zn(O,Se) phase were formed only at 500 °C. The lattice parameters monotonously decreased with both increasing deposition temperature and lowering Se concentrations in the films. The electron density increased significantly from 1.0 × 10 14 to 3.2 × 10 18 when changing the substrate temperature from 500 to 550 °C. We attributed these changes to the formation of vacancy-type defects in the Zn(O,Se) system. For the first time, we demonstrated the applicability of Zn(O,Se) as a buffer layer in a complete solar cell structure. We developed a prospective superstrate configuration FTO/Zn(O,Se)/CdTe/Te/Ni solar cell exhibiting a cell efficiency of 7.6% (FTO, fluorine-doped tin oxide). Our findings revealed the great potential of Zn(O,Se) to replace conventional CdS buffer layers and to open up new strategies to improve solar cell performance.

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A cost-effective dopant-free fluorene-based enamine as a hole transport material for semi-transparent Sb2S3 solar cells is successfully demonstrated.