We fabricated polycrystalline Cu2ZnGe x Sn1–x Q4 (Q = S or Se) thin films by using spray-based deposition. The effects of Ge alloying were studied by X-ray diffraction (XRD), Raman spectroscopy, and UV–visible spectroscopy. XRD and Raman spectroscopy revealed that lattice parameters decreased linearly and characteristic Raman peaks shifted to higher frequency with increasing Ge alloying. The band gap energies of postsulfurized CZGTS films (1.51 ± 0.05 to 1.91 ± 0.05 eV) and postselenized CZGTSe films (1.07 ± 0.05 to 1.44 ± 0.05 eV) increased almost linearly with an increase of Ge alloying in the respective films. Analysis of band gap bowing model showed a small bowing constant b ∼ 0.1 ± 0.02 eV, indicating high miscibility of alloyed elements. The band gap tuning of CZGTS­(Se) thin films can be utilized for tuning band gap of subcell in multijunction cell and for band gap graded photoabsorber of high efficient solar cell.

CZFTS) thin films have been fabricated using chemical spray pyrolysis accompanied by postsulfurization. The postsulfurized CZFTS films demonstrate promising morphological, structural, and optical properties for photoabsorber in thin film photovoltaics. The structural transition from stannite to kesterite is found with the increase of zinc content in CZFTS alloy by using X-ray diffraction and Raman spectroscopy. The band gap energies of postsulfurized CZFTS films are observed to be tuned from ∼1.36 ± 0.02 to 1.51 ± 0.02 eV in parabolicincrease trend with increasing Zn content (0 ≤ z ≤ 1). A small bowing constant b ∼ 0.1 ± 0.05 eV deduced from band gap bowing model implicates good miscibility of alloyed constituents in the host crystal lattice.

We analyzed and compared quantitatively the optoelectronic characteristics of perovskite PV devices with and without annealing the perovskite layer in a methyl ammonium chloride vapor atmosphere (MACl treatment).

The performance of perovskite device was found to be influenced by the interface quality and bulk defect activities induced in perovskite grown on HTL during device fabrication.

We report on the fabrication of polycrystalline Cu 2 ZnGeX 4 (X = S, Se) thin films using spray pyrolysis followed by post-sulfurization and post-selenization. The stoichiometric, morphological, structural and optical properties of fabricated thin films were investigated and discussed in the photovoltaic aspect. Although the as-sprayed films were observed to be grown with poor crystalline texture, the crystallinity was found to be greatly improved after post-sulfurization and post-selenization, which was confirmed by X-ray diffraction (XRD) and Raman spectroscopy. The band gap energy was estimated as 1.88-1.93 eV for post-sulfurized Cu 2 ZnGeS 4 (CZGS) films and 1.40-1.43 eV for post-selenized Cu 2 ZnGeSe 4 (CZGSe) films by UV-Vis absorption measurements. The crystal lattice parameters calculated from XRD patterns for post-sulfurized CZGS and post-selenized CZGSe films were found to be consistent with kesterite structure which is strongly supported by the band gap energy estimated from the UV-Vis absorption measurements.

Antisolvent treatment followed by solvent vapor annealing affected the morphology of the caesium bismuth halide film and impacted the device parameter tuning by the carrier transport layer.

Wide-band-gap (WB) perovskite devices are promising as the top cell of silicon-perovskite tandem devices to boost the efficiency beyond the Shockley-Queisser limit. Here, we tailor the performance parameters of WB mixed-halide perovskite solar cell with long alkyl chain-substituted fullerene derivatives as an electron transport layer (ETL). The device with C-fused N-methylpyrrolidine- meta-dodecyl phenyl (CMC) demonstrates an enhanced power conversion efficiency of 16.74% with the record open circuit voltage ( V) of 1.24 V, an increase by 70 mV with concomitant V deficit reduction to 0.47 V. This is achieved by mitigating the recombination loss through the use of highly crystalline CMC film compared to amorphous [6,6]-phenyl-C-butyric acid methyl ester layer. The device analysis reveals the soothing of the defect activities with shallower defect states and passivation of the interface recombination centers for the device with CMC. We ascribe this property to the crystallinity of fullerene derivatives as ETL, which is also important for the optimization of device parameters, besides the band alignment matching of WB perovskite devices.

Cd-free kesterite-based Cu 2 ZnSnSe 4 (CZTSe)/In 2 S 3 champion solar cell of 5.74% efficiency has been fabricated by chemical spray pyrolysis. In this fabrication route, CZTSe absorber layer was sprayed by using a precursor solution, where metallic salts were dissolved in water-based solvent and subsequently selenized with Se powder at high temperature. In 2 S 3 buffer as an alternative to CdS buffer was also deposited by chemical spray pyrolysis. The device characteristics were studied by measuring dark/light illuminated J−V−T, external quantum efficiency, temperature dependence of open circuit voltage (V OC ) and series resistance (R s ), and admittance spectroscopy. The performance of sprayed CZTSe/ In 2 S 3 solar cell was found to be limited by high back-contact barrier potential, poor carrier collection, and detrimental intrinsic defect states in device.