Hailin Luo

Abnormal piezoresponse behavior of Pb(Mg1/3Nb2/3)O3–30%PbTiO3 single crystal studied by high-vacuum scanning force microscope

The piezoresponse behavior dependence of the Pb(Mg1/3Nb2/3)O3-30%PbTiO3 single crystal on the vacuum degree has been investigated by scanning force microscopy in the piezoresponse mode under high vacuum. Unusual piezo-response behavior related to the screening charges compensation mechanism is observed on the (111) crystal face. The significant piezoresponse degradation behavior with low piezoresponse signal under high vacuum is attributed to the instability of the polarization state due to the insufficient compensation of the intrinsic screening charges for the polarization charges in PMN-30%PT single crystal. In contrast, the remarkable domain contrast of the sample at ambient pressure is owing to the dominant surface screening charges deriving from surface adsorption, which plays an important role in determining the stability of the domain behavior and in achieving the optimal properties.

A low-temperature formation path toward highly efficient Se-free Cu2ZnSnS4 solar cells fabricated through sputtering and sulfurization

A novel low-temperature Cu2ZnSnS4 (CZTS) formation path using co-sputtered SnS2–ZnS–Cu precursors was employed for CZTS solar cell fabrication, which gave rise to a cell with a power conversion efficiency of 8.58%, a big step forward from the previous record of 6.77% reported by Katagiri et al. for this kind of solar cell. This method consists of a low-temperature annealing stage for CZTS phase formation followed by a short high-temperature annealing stage for grain growth and secondary phase removal. The employment of SnS2 as a precursor causes the CZTS phase to readily form at low temperature when SnS2 has not dramatically decomposed into volatile SnS. The two-stage process wisely separates the phase formation and crystal coalescence, which makes the fabrication of CZTS films more controllable. Furthermore, the demonstration of the low-temperature formation path provides new opportunities to fabricate highly efficient, cost-effective and environmentally friendly CZTS solar cells on low-weight and flexible substrates such as polyimides.

Distribution and formation mechanism of the domain structure in PMN?33% PT single crystals

Domain structures investigation in (110)-oriented Pb(Mg1/3Nb2/3)O3–33% PbTiO3 (PMN–33% PT) single crystals has been performed by piezoresponse force microscopy. Submicron-sized fingerprint pattern and tweed pattern domains (TPDs) have been observed in large parallel domains with typical sizes of 20–30 µm. Based on the existence of gradual transition regions between fingerprint pattern domains and TPDs in the same large ferroelectric domain, the relationship between the two pattern domains is discussed and a possible formation mechanism of the domain structure in PMN–33% PT single crystal is proposed.

Application of CVD graphene as transparent front electrode in Cu(In,Ga)Se 2 solar cell

Graphene is a promising material to be used as transparent conducting electrode (TCE) due to its high optical transmittance and conductivity. In this work, we present a novel TCE structure for the Cu(In,Ga)Se2 (CIGS) solar cell in which a AuCl3 doped graphene film grown by chemical vapor deposition (CVD) with a thin layer of PMMA coating was used to replace the ZnO:Al (AZO) film. The Ni/Al/Ni metal grid was directly deposited on the intrinsic high resistivity ZnO (i-ZnO) buffer layer. And large area (~ 0.5 cm2) PMMA/graphene layer was transferred to contact both metal grid and i-ZnO. Our findings demonstrate that FF, Jsc and PCE will be improved when silver nanowires are present at the graphene/i-ZnO interface in the CIGS solar cell. To further increase the solar cell performance, the pattern of the metal grid was also simulated and optimized.

The opportunity and challenge of CIGS solar cells

In this paper, the background, structure, principle and history of CIGS solar cells are introduced. And based on the discussion on the major development of CIGS technologies and fundamental mechanisms, three suggestions are proposed for the industrial development of CIGS technologies: energy band optimizing, substitution of indium and substitution of cadmium. Furthermore, the future of the CIGS industry in China is also proposed.