The effects of deposition time of the second stage (t2nd) and the third stage (t3rd) during the three-stage process on the formation of Cu-deficient layers (CDLs) at Cu(In,Ga)Se2 (CIGS) near-surface were investigated in this study. The experimental findings suggested that the CDL was thickened by a longer deposition time in the third stage. Also, the device performance was found to deteriorate with the increased thickness of CDLs, suggesting that the CDL has a defect concentration higher than that of CIGS thin films. Furthermore, the peak position of electron beam induced current signal was shifted towards the interior region of CIGS films, confirming the n-type conductivity of CDLs. The highest conversion efficiency of 19.0% was obtained in this work when the thickness of CDL was 80 nm.

Earth-abundant and environmentally benign antimony selenide (Sb2Se3) has emerged as a promising light-harvesting absorber for thin-film photovoltaic devices due to its high absorption coefficient, nearly ideal bandgap for photovoltaic applications, excellent long-term stability, and intrinsically benign boundaries if properly aligned on the substrate. The record power conversion efficiency (PCE) of Sb2Se3 solar cells has currently reached 9.2%, however, it is far lower than the champion efficiencies of other chalcogenide thin-film solar cells such as CdTe (22.1%) and Cu(In,Ga)Se2 (23.35%). The inferior device performance of Sb2Se3 thin-film solar cells mainly results from a large open-circuit voltage deficit, which is strongly related to the interface recombination loss. Accordingly, constructing proper band alignments between Sb2Se3 and neighboring charge extraction layers through interface engineering to reduce carrier recombination losses is one of the key strategies to achieving high-efficiency Sb2Se3 solar cells. In this review, the fundamental properties of Sb2Se3 thin films, and the recent progress made in Sb2Se3 solar cells are outlined, with a special emphasis on the optimization of energy band alignments through the applications of electron-transporting layers and hole-transporting layers. Furthermore, the potential research directions to overcome the bottlenecks of Sb2Se3 thin-film solar cell performance are also presented.

Sb2Se3 possesses a quasi‐1D (Q1D) structure, which creates an anisotropic charge transporting behavior in which the carrier transport is very efficient along the Q1D direction, which is beneficial for solar cells as long as the absorber is properly aligned along the preferred orientation. However, Sb2Se3 is prone to form donor‐like defects, such as VSe, that are detrimental to the performance. Therefore, both growth of Sb2Se3 along the preferred orientations and the suppression of the formation of VSe are crucial in achieving Sb2Se3 solar cells with a high efficiency. Herein, the importance of fine control of the extra supply of Se during the deposition of Sb2Se3 in controlling crystallographic orientations and the population of VSe in the Sb2Se3 films is described. This control determines the performance of the resulting solar cells in a superstrate configuration with a CdS buffer. Incorporation of Se during the growth resulted in a larger open‐circuit voltage due to the passivation of VSe. However, an excess supply of Se disrupts the favorable orientation by selenizing the top region of the CdS, and therefore degraded the short‐circuit current. Through the optimization of the extra supply of Se vapor, the power conversion efficiency is improved from 3.7% to 5.2%.

Sb2Se3, a quasi-1D structured binary chalcogenide, has great potential as a solar cell light absorber owing to its anisotropic carrier transport and benign grain boundaries when the absorber layer is...

Zinc tin nitride (ZTN) compounds exhibit excellent optical and defecttolerance properties desirable for optoelectronic applications. However, the synthesis of high-phase-purity ZTN is limited by oxidation. We report the synthesis of amorphous ZTN films with excellent oxidation resistance for a wide range of compositions (from pure Zn 3 N 2 to ZTN with Sn/(Sn + Zn) up to 66.9%). We employ modified pulsed plasma-enhanced chemical vapor deposition with alternating pulses of zinc and tin precursors. We observe a correlation between oxidation resistance and pulse duration of the Zn precursor. Furthermore, extensive structural, chemical, electrical, and optical characterizations are discussed for amorphous ZTN with varying Sn/Zn. Electron microscopy reveals a mixture of nanoscale domains with Zn-rich and Sn-rich phases in the synthesized films. Interestingly, the trends of the electrical and optical properties vs the Sn content of amorphous ZTN are similar to reported crystalline ZTN. Notably, amorphous ZTN of Sn/(Zn + Sn) ∼ 0.3 exhibited a carrier concentration of 5.3 × 10 13 cm −3 , the lowest among those reported for ZTN of any composition, making it very promising for photovoltaic applications. Our study presents a new class of compounds with materials properties that are unaccessible by the conventional crystalline nitrides, which will be useful for future optoelectronic applications.