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The first step in the fabrication of SHJ (silicon heterojunction) solar cells is forming random pyramids on the Si wafer surfaces. The pyramid profile would affect the following amorphous silicon deposition. Two CP (chemical polishing) solutions consist of HNO3 + HF and O3 + HF, respectively, are used to modify the pyramid profile. It is found that these two solutions have selective rounding effects on the pyramid profiles. The first one rounds the pyramid valleys and the second one rounds the pyramid peaks. The combination of the two CP methods improves the passivation quality of amorphous silicon and promotes the conversion efficiency of SHJ cells.

In the two-step selenization process, Ga accumulation near back contact is a common problem, resulting in a lower band gap near front surface and then lower open circuit voltage (VOC) of solar cell. In this work, Ga accumulation in Cu(In, Ga)(S, Se)2 (CIGSSe) film was weakened by pre-sulfurized and selenized (PSS) Mo back contacts. The sputtered dense Mo back contacts were sulfurized and selenized at different temperatures before Cu-In-Ga precursor deposition. Raman results show that MoS2, MoSe2 and pure Se phases were formed on the PSS Mo surface. These selenide and sulfide phases will become the bottom Se and S sources in the structure of PSS Mo/metal precursor during selenization process. The thermodynamic calculation confirms the bottom S and Se sources are effective. SIMS measurement shows the Ga back grading in CIGSSe films decreases when the PSS Mo back contacts are used. For higher substrate temperature (Tsub) we find reduced steepness of the Ga back gradient. The S atomic percentage in CIGSSe is so small that the band gaps of CIGSSe are mainly determined by the Ga/(Ga + In) distribution. Therefore, the band gap in the space charge region (SCR) of solar cell increased when PSS Mo was used. As expected, VOC increased about 10 mV when TSub increased to 600 °C. Due to the enhancement of VOC and fill factor (FF), the conversion efficiencies (η) of solar cells was improved.

Numerical simulation of inverted planar perovskite solar cells based on NiO x hole transport layer was performed with AMPS-1D program. The simulated device parameters were shown to agree well with our experimental work. The simulated results revealed that the device contained typical p-i-n junction configuration. The optimum thickness of the absorber, the effects of the absorber quality, the defect density of interfaces, the effects of VBO and CBO, the interface contact at front and back electrodes were analyzed. Open-circuit voltage mainly depended on the defect density in CH 3 NH 3 PbI 3 layer, the recombination at HTL/CH 3 NH 3 PbI 3 and ETL/CH 3 NH 3 PbI 3 interface, the values of VBO and CBO, while short-circuit current mainly depended on the thickness of CH 3 NH 3 PbI 3 layer. Fill factor was significantly influenced by the interface contact at front and back electrodes. Remarkably, a power conversion efficiency of 21.8% is obtained under optimised conditions. Real devices with PCE of up to 15% were obtained by initially optimizing the preparation of CH 3 NH 3 PbI 3 absorber layer. Our work can provide some important guidance for device design and optimization from the considerations of both theory and experiment.

Intermediate phase film (MAI-PbI2-DMSO) with [0 0 2] preferential crystalline orientation was prepared, which was not stable at room temperature. Many pinholes form by directly heating it at 100 °C. Smooth and homogeneous MAPbI3 films can be obtained by adding a stage of low temperature preheating process to restrain the rapid effusion of DMSO molecules. A high PCE of 15.43% was achieved for NiOx-based inverted planar perovskite solar cells.

n-type CZ-Si wafers featuring longer minority carrier lifetime and higher tolerance of certain metal contamination can offer one of the best Si-based solar cells. In this study, Si heterojuction (SHJ) solar cells which was fabricated with different wafers in the top, middle and tail positions of the ingot, exhibited a stable high efficiency of > 22% in spite of the various profiles of the resistivity and lifetime, which demonstrated the high material utilization of n-type ingot. In addition, for effectively converting the sunlight into electrical power, the pyramid size, pyramid density and roughness of surface of the Cz-Si wafer were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). Furthermore, the dependence of SHJ solar cell open-circuit voltage on the surface topography was discussed, which indicated that the uniformity of surface pyramid helps to improve the open-circuit voltage and conversion efficiency. Moreover, the simulation revealed that the highest efficiency of the SHJ solar cell could be achieved by the wafer with a thickness of 100 μm. Fortunately, over 23% of the conversion efficiency of the SHJ solar cell with a wafer thickness of 100 μm was obtained based on the systematic optimization of cell fabrication process in the pilot production line. Evidently, the large availability of both n-type ingot and thinner wafer strongly supported the lower cost fabrication of high efficiency SHJ solar cell.

The simultaneous selenization/sulfurization is investigated to fabricate Cu(In, Ga)(Se,S) 2 thin films in the H 2 S/H 2 Se/N 2 hybrid gas, and the optical band gap of Cu(In, Ga)(Se,S) 2 thin film is adjusted from 1.05 eV to 1.22 eV by varying the concentration ratio of H 2 S/H 2 Se. It is found that more S incorporates into the CIGSeS phase when the H 2 S concentration is increased, which widens the band gap of CIGSeS alloy. Furthermore, the through-film element profile of the CIGSeS films with different reaction time reveals that CIGSeS film is Ga-poor and S-poor during the initial reaction, and Ga and S are redistributed during the subsequent reaction with a joint of H 2 S and H 2 Se.

Cu(In, Ga)Se2 (CIGS) thin films with thickness of 1 μm and 2 μm are prepared by co-evaporation process, and the different Ga/(Ga + In) are achieved by varying the temperature of Ga source. The morphology, structure, minimum band gap, and performance of solar cells are comparatively studied. As Ga/(Ga + In) increases, little changes can be observed in the crystal quality of 1 μm CIGS films, while the grain size of 2 μm films decreases significantly. (112) diffraction peak intensities of the 1 μm and 2 μm films decrease and increase, respectively. In the case of the same Ga/(Ga + In), the minimum band gap values of 1 μm films are larger than that of 2 μm films, and the difference becomes large with Ga/(Ga + In) increasing. The minimum band gap values of 1 μm films are more sensitive to variation of the Ga/(Ga + In). As Ga/(Ga + In) increases, a more improvement of the efficiency of solar cells with thickness of 1 μm is obtained due to the large enhancement of the open-circuit voltage, and the efficiency reaches the maximum value when Ga/(Ga + In) is about 0.37.

Correlation between surface passivation of crystalline silicon and the microstructure of silicon passivation layer has been investigated. Based on the optical constants determined by Spectroscopic Ellipsometry measurements, effective medium approximations has been employed to simulate the microstructure of silicon thin film with the mixed phase, including amorphous structure and spherical or ellipsoidal crystallites. A key factorf c , describes the volume fraction of nanocrystallites in the amorphous network, has a significant role to improve the fill factor of silicon heterojunction solar cells. Moreover, the cell performance can be improved by the increasing material density of intrinsic silicon interface layer.

This study examines the effects of four cadmium sources on the properties of cadmium sulfide (CdS) thin films prepared using chemical bath methods. The reaction solutions used cadmium acetate, cadmium sulfate, cadmium iodide and cadmium chloride as cadmium sources. The surface morphology, crystal structure, optical properties and impurities absorption of CdS films were analyzed. The CdS films deposited with different Cd sources showed similar crystalline structures and surface morphologies. In addition, the Cd film band gaps differed unobviously. Measurements made with Fourier transform infrared spectrum showed that CN bonds were the main impurities absorbed in the CdS films. After the CdS films had been annealed at 120 °C in air, the CN peak intensity for cadmium acetate, cadmium sulfate and cadmium chloride decreased while the CN peak intensity for cadmium iodide increased. We found that the performance of a copper indium gallium selenide (CIGS) solar cell was influenced by the Cd sources; this was especially true for the fill factor (FF). Higher values of CN bonds absorption yielded lower values of FF and conversion efficiency of CIGS solar cells. Among the four tested Cd sources, cadmium acetate and cadmium sulfate proved much more suitable as Cd sources for depositing CdS thin films.

A cosputtered Cu–In–Ga metal precursor was first selenized in H2Se atmosphere, and then subsequently annealed in N2 atmosphere. The microstructural evolution of Cu(In1− x Ga x )Se2 (CIGS) films during thermal treatment was investigated, and it was found that the morphology and Ga distribution of the CIGS absorber were governed by selenization and annealing. The intermediate phases InSe and Cu9(In1− x Ga x )4 formed in the selenization step are beneficial to Ga diffusion and grain growth during annealing. Therefore, the open-circuit voltage and fill factor of a CIGS solar cell were enhanced by the combination of a sufficient amount of intermediate phases and 580 °C annealing, attributed mainly to the higher Ga content near the front surface and better crystallinity of the CIGS absorber. The conversion efficiency of CIGS solar cell was increased 1.24-fold with optimized selenization and annealing conditions.