Recent progress and perspectives on Sb_(2)Se_(3)-based photocathodes for solar hydrogen production via photoelectrochemical water splitting

Photoelectrochemical(PEC) cells involved with semiconductor electrodes can simultaneously absorb solar energy and perform chemical reactions, which are considered as an attractive strategy to produce renewable and clean hydrogen energy. Sb_(2)Se_(3) has been widely investigated in constructing PEC photocathodes benefitting of its low toxicity, suitable band gap, superior optoelectronic properties, and outstanding photocorrosion stability. We first present a brief overview of basic concepts and principles of PEC water splitting as well as a comparison between Sb_(2)Se_(3) and other numerous candidates. Then the material characteristics and preparation methods of Sb_(2)Se_(3) are introduced. The development of Sb_(2)Se_(3)-based photocathodes in PEC water splitting with various architectures and engineering efforts(i.e., absorber engineering, interfaces engineering, co-catalyst engineering and tandem engineering) to improve solar-to-hydrogen(STH) efficiency are highlighted. Finally, we debate the possible future directions to further explore the researching fields of Sb_(2)Se_(3)-based photocathodes with a strongly positive outlook in PEC processed solar hydrogen production.

High-efficiency ultra-thin Cu_(2)ZnSnS_(4) solar cells by double-pressure sputtering with spark plasma sintered quaternary target

In recent years,Cu_(2)ZnSnS_(4)(CZTS)semiconductor materials have received intensive attention in the field of thin-film solar cells owing to its non-toxic and low-cost elements.In this work,double-pressure sputtering technology is applied to obtain highly efficient and ultra-thin(-450 nm)pure Cu_(2)ZnSnS_(4)(CZTS)solar cell.Using mixed materials with sulfides and copper powder as a quaternary target via spark plasma sintering(SPS)method and adopting double-layer sputtering(high+low pressure),a highly adhesive and large-grained CZTS thin film is achieved.As a result,the damage to the surface of Mo contact is decreased so that the reflectivity of incident light can be improved.Moreover,the composition of CZTS film was more uniform and the secondary phase separation at the Mo interface was reduced.Therefore,the interface defect state and deep level defect density in corresponding device with double-pressure is reduced and the ratio of depletion thickness to absorption layer thickness can reached to 0.58,which promoted the collection of photogenerated carriers.Finally,an efficiency of 9.3%for ultra-thin(~450 nm)CZTS film solar cell is obtained.

Over 12%efficient kesterite solar cell via back interface engineering

Kesterite Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)has attracted considerable attention as a non-toxic and earthabundant solar cell material.During selenization of CZTSSe film at high temperature,the reaction between CZTSSe and Mo is one of the main reasons that result in unfavorable absorber and interface quality,which leads to large open circuit voltage deficit(VOC-def)and low fill factor(FF).Herein,a WO_(3)intermediate layer introduced at the back interface can effectually inhibit the unfavorable interface reaction between absorber and back electrode in the preliminary selenization progress;thus high-quality crystals are obtained.Through this back interface engineering,the traditional problems of phase segregation,voids in the absorber and over thick Mo(S,Se)_(2)at the back interface can be well solved,which greatly lessens the recombination in the bulk and at the interface.The increased minority carrier diffusion length,decreased barrier height at back interface contact and reduced deep acceptor defects give rise to systematic improvement in VOCand FF,finally a 12.66%conversion efficiency for CZTSSe solar cell has been achieved.This work provides a simple way to fabricate highly efficient solar cells and promotes a deeper understanding of the function of intermediate layer at back interface in kesterite-based solar cells.

Microstructure and 355 nm Laser-Induced Damage Characteristics of Al₂O₃Films Irradiated with Oxygen Plasma under Different Energy

Al2O3 films were prepared using electron beam evaporation at room temperature. The samples were irradiated with oxygen plasma under different energy. The variations in average surface defect density and root mean square (RMS) surface roughness were characterized using an optical microscope and an atomic force microscope. Surface average defect density increased after plasma treatment. The RMS surface roughness of the samples decreased from 1.92 nm to 1.26 nm because of surface atom restructuring after oxygen plasma conditioning. A 355 nm laser-induced damage experiment indicated that the as-grown sample with the lowest defect density exhibited a higher laser-induced damage threshold (1.12 J/cm2) than the other treated samples. Laser-induced damage images revealed that defect is one of the key factors that affect laser-induced damage on Al2O3 films.

Ion doping simultaneously increased the carrier density and modified the conduction type of Sb_(2)Se_(3) thin films towards quasi-homojunction solar cell

Antimony selenide(Sb_(2)Se_(3))has drawn tremendous research attentions in recent years as an environment-friendly and cost-efficient photovoltaic material.However,the intrinsic low carrier density and electrical conductivity limited its scope of applications.In this work,an effective ion doping strategy was implemented to improve the electrical and photoelectrical performances of Sb_(2)Se_(3) thin films.The Sn-doped and I-doped Sb_(2)Se_(3) thin films with controllable chemical composition can be prepared by magnetron sputtering combined with post-selenization treatment based on homemade plasma sintered targets.As a result,the Sn-doped Sb_(2)Se_(3) thin film exhibited a great increase in carrier density by several orders of magnitude,by contrast,a less increase with one order of magnitude was achieved for the Idoped Sb_(2)Se_(3) thin film.Additionally,such cation or anion doping could simultaneously modify the conduction type of Sb_(2)Se_(3),enabling the first fabrication of a substrate structured Sb_(2)Se_(3)-based quasihomojunction thin film solar cell with configuration of Mo/Sb_(2)Se_(3)-Sn/Sb_(2)Se_(3)-I/ITO/Ag.The obtained power conversion efficiency exceeding 2%undoubtedly demonstrated its attractive photovoltaic application potential and further investigation necessity.