The effect of grain boundaries (GBs), in particular twin boundaries (TBs), on CdTe polycrystalline thin films is studied by conductive atomic force microscopy (C-AFM), electron-beam-induced current (EBIC), scanning Kelvin probe microscopy (SKPM), electron backscatter diffraction (EBSD), and scanning transmission electron microscopy (STEM).

CdTe thin films were grown by RF magnetron sputtering at deposition pressures of 1.5–4 Pa and substrate potentials of 8.8, 0, −8.2, −18.9, −28.3, −38.1, −48.0, and −98.7 V. All as-grown CdTe thin films had undergone CdCl₂ treatment in dry air. The deposition pressure had a large influence on the crystalline quality, morphology, and grain size. At 1.5–3 Pa, CdTe thin films with good crystalline quality and column morphology were successfully obtained. The substrate potential also influenced the phase composition, grain size, morphology, microstress, and roughness of the obtained CdTe thin films. The phase composition, morphology, grain size, microstress, and crystalline quality changed significantly after CdCl₂ annealing treatment. For CdTe grown at 3 Pa, the grain size reached a maximum when the Cl treatment time was 20 min; for CdTe thin films deposited at 2 Pa, grain size was the greatest when the Cl treatment time was 43 min. The maximum grain size corresponded to the best performance of the CdTe solar cell. CdTe thin films grown at different substrate potentials were subjected to Cl treatment at 400 °C for 43 min. The internal structure was observed using scanning electron microscopy of sample cross-sections sliced by a focused ion beam. After Cl treatment, voids were seen at the CdTe grain boundaries, and at the interfaces CdS/F:SnO₂ and CdS/CdTe. The CdTe film grown at a substrate potential of −18.9 V produced the best solar cell, with device parameters of η = 12.78%, V_oc = 779 mV, J_sc = 22.91 mA cm⁻², and FF = 71.62%.

The Ga doped ZnO (GZO) film is one of the promising alternative films to replace ITO film, but its properties suffer from degradation when it is deposited under oxygen-rich conditions. This degradation has been investigated by depositing the films under different oxygen partial pressures. XRD results showed that all GZO films had wurtzite structure and the lattice parameter-c contracted when oxygen was introduced into the argon deposition atmosphere, but the parameter-c nearly remained constant when oxygen partial pressures were further increased. The contraction of parameter-c was caused by the increasing concentrations of V_Zn (Zn vacancy). It was the first time to observe that the impurity phase of Ga₂Zn₆O₉ appeared and disappeared in GZO films during the increase of oxygen partial pressures. Analogously, conductivity decayed and optical bandgap decreased abruptly as oxygen was introduced, which enhanced self-compensation of donors and acceptors. The energy band structures of GZO and ZnO films were determined by using UPS, and the results showed that oxygen had little effect on the electron affinity of the GZO film, but a significant difference in electron affinity between the ZnO and GZO films was observed. This result indicated that although the electron affinity of ZnO could be effectively tuned by doping with Ga, it remained quite stable for GZO under oxygen-rich conditions.

Thin-film photovoltaic technology has begun to be applied in building-integrated photovoltaics (BIPVs), and it is believed that thin-film photovoltaic technology has potential in building-integrated photovoltaic applications. In this paper, a hybrid approach was investigated which combined the maximum power point tracking (MPPT) algorithm of three-stage variable step size with continuous conduction mode (CCM)/discontinuous current mode (DCM). The research contents of this paper include the principle analysis of the maximum power point tracking algorithm, the design of the sampling period, and the design of a double closed-loop control system and correction factor. A system model was built in MATLAB/Simulink, and a comparative simulation was carried out to compare the performance of the proposed method with some traditional methods. The simulation results show that the proposed approach has the ability to fast-track and make the system run stably. Furthermore, it can make the system respond quickly to environmental changes. An experimental platform was built, and the experimental results validated and confirmed the advantages of the proposed method.

Cadmium telluride (CdTe) photovoltaics is a promising and scalable technology, commanding over 90% of the thin film photovoltaics market. An appropriate window layer is crucial for high-efficiency CdTe solar cells. This study aimed to investigate a representative MgZnO (MZO) window layer and enhance device performance. We studied the properties of MZO films with different substrate temperatures and their application in CdSeTe/CdTe solar cells. Despite the high transmittance and wide band gap of MZO film, the device performance of MZO sputtered at room temperature is limited by excessive conduction band offset. Tailoring the substrate temperature for MZO sputtering helps optimize the band alignment of the MZO/CdSeTe interface, contributing to an improvement in the efficiency of CdTe solar cells.