Nanocrystalline hydrogenated silicon (nc-Si:H) substrate configuration n-i-p solar cells have been fabricated on soda lime glass substrates with active absorber layers prepared by plasma enhanced chemical vapor deposition (PECVD) and radio frequency magnetron sputtering. The cells with nanocrystalline PECVD absorbers and an untextured back reflector serve as a baseline for comparison and have power conversion efficiency near 6%. By comparison, cells with sputtered absorbers achieved efficiencies of about 1%. Simulations of external quantum efficiency (EQE) are compared to experimental EQE to determine a carrier collection probability gradient with depth for the device with the sputtered i-layer absorber. This incomplete collection of carriers generated in the absorber is most pronounced in material near the n/i interface and is attributed to breaking vacuum between deposition of layers for the sputtered absorbers, possible low electronic quality of the nc-Si:H sputtered absorber, and damage at the n/i interface by over-deposition of the sputtered i-layer during device fabrication.

Glancing angle deposition (GLAD) of CdTe can produce a cubic, hexagonal, or mixed phase crystal structure depending upon the oblique deposition angles (Φ) and substrate temperature. GLAD CdTe films are prepared at different Φ at room temperature (RT) and a high temperature (HT) of 250 °C and used as interlayers between the n-type hexagonal CdS window layer and the p-type cubic CdTe absorber layer to investigate the role of interfacial tailoring at the CdS/CdTe heterojunction in photovoltaic (PV) device performance. The Φ = 80° RT GLAD CdTe interlayer and CdS both have the hexagonal structure, which reduces lattice mismatch at the CdS/CdTe interface and improves electronic quality at the heterojunction for device performance optimization. The device performance of HT CdS/CdTe solar cells with Φ = 80° RT with 50 to 350 nm thick GLAD CdTe interlayers is evaluated in which a 250 nm interlayer device shows the best device performance with a 0.53 V increase in open-circuit voltage and fill-factor product and a 0.73% increase in absolute efficiency compared to the HT baseline PV device without an interlayer.

Thermodynamic, structural, surface, and transport properties of Au-Ni liquid alloy at 1150 K were computed using different theoretical approaches. The thermodynamic properties, such as excess Gibbs free energy of mixing, enthalpy of mixing, activity and excess entropy of mixing, and structural properties, such as concentration fluctuation in long-wavelength limit and Warren-Cowley short-range order parameter were computed in the framework of Flory’s model. The effect of positive and negative values of the interchange energy parameter on the excess Gibbs free energy of mixing and concentration fluctuation in the long-wavelength limit was also observed. The surface tension and surface concentration of the system were calculated using Butler’s model. In the transport property, the viscosity of the system was calculated using Kaptay and Budai-Benko-Kaptay (BBK) models. BIBECHANA 18 (2021) 184-192

Non-contacting optical probes based on spectroscopic ellipsometry or reflectance measurements are used to predict photovoltaic (PV) device performance and to diagnose optical and electronic losses. Optical modeling of aluminum back surface field (Al-BSF) silicon, thin film cadmium telluride (CdTe), and hybrid organic inorganic lead halide based perovskite (FA_1−xCs_xPbI₃) solar cell technologies are reviewed. Using the near infrared (IR) to ultraviolet (UV) optical properties of PV device component materials and the device structures as input, external quantum efficiency (EQE) spectra are simulated for Al-BSF, CdTe, and perovskite solar cells for comparison with experimental EQE and short circuit current density (J_SC). Optical Hall effect measurements of Al-BSF PV determine majority and minority carrier transport properties in the n+ emitter and p-type wafer silicon; from this information open circuit voltage (V_OC), fill factor (FF), J_SC, and power conversion efficiency (PCE) are calculated and agree well with direct current-voltage (J-V) electrical measurement. An IR-extended optical model for Al-BSF silicon PV includes coherent multiple reflections, ray tracing optics, and diffuse scattering and is applicable as a baseline for developing optical and thermal management strategies. Analysis of EQE for CdTe based solar cells with selenium alloying (CdSe_1−yTe_y) enables determination of absorber composition after full device processing. EQE modeling for perovskite solar cells includes the ability to account for sub gap absorption measured in films but not present in the solar cell absorber and incomplete photogenerated carrier collection in the PV device.