Sb₂Se₃ Thin Film Solar Cells And Its Potential Application For Internet Of Things

With the advent of the 5G era,the intelligent system of the Internet of Things(Io T)has developed rapidly,and the demand for Io T devices shows an exponential growth trend.The long-term stable energy supply of the sensor node in Io T system is one of the critical problems to be solved.For the sensor node that is difficult to access power,utilizing high-power density of solar cells combining with energy storage technologies such as lithium battery is one of the most competitive technologies to solve the energy supply problem.Inorganic thin-film solar cells,due to their characteristics of lightweight,good stability and excellent weak-light performance,can serve as the long-term supplier for these sensor nodes.The trend towards miniaturization,high integration,and low-cost of Io T sensor nodes also requires solar cells to be efficient,flexible,lightweight and inexpensive.Sb₂Se₃ material has excellent optoelectric properties,and the theoretical efficiency of a single-junction solar cell can reach 31.7%.With the high abundance and low price of Sb and Se,and the deposition of Sb₂Se₃ onto the polymer substrate at low temperature,low-cost manufacturing of Sb₂Se₃thin film solar cells are expected.It is thus very promising to make low-cost,high-efficiency,and lightweight Sb₂Se₃ thin-film solar cells for energy supply in the Io T.However,at the beginning of this project,the efficiency of Sb₂Se₃ solar cells was only6.5%,showing great room for improvement.Meanwhile,flexible Sb₂Se₃ solar cells have not been reported.Studies suggest that defect recombination and crystal orientation are the main limiting factors for efficiency improvement of Sb₂Se₃ thin-film solar cells.At the same time,construction of flexible Sb₂Se₃ devices have also become the core challenge for their Io T applications.This thesis aims at the core challenges of efficiency and flexibility of Sb₂Se₃ solar cells.We take the lead in the preparation of efficient,stable,and flexible Sb₂Se₃thin-film solar cells through the construction of suitable hole transport layer,crystal orientation controlling,and the deep understanding of its mechanical properties.Our study demonstrates the competitive application for the power supply of the Io T and point out the further research direction for Sb₂Se₃ thin-film solar cells.The specific contents include:(1)A n-i-p structured Sb₂Se₃ thin-film solar cell was constructed by using CuSCN as the hole collection layer.With Cuion out-diffusion,it not only causes the grain boundary inversion in Sb₂Se₃ film to inhibit carrier recombination,but also increases the Cuvacancies in CuSCN to improve its doping density and promote an effective collection of photogenerated carriers.Finally,the efficiency of Sb₂Se₃ thin-film solar cells was improved from 6.5%to 7.5%.(2)Based on the one-dimensional crystal structure characteristics of Sb₂Se₃ material,the[hkl,l?0]-oriented Sb₂Se₃ seeds were obtained by seed screening method,consequently producing Sb₂Se₃ film with preferred[hkl,l?0]orientation.In Sb₂Se₃ thin-film solar cell with this optimized orientation,photogenerated carrier can efficiently transport along the molecular chain,and the short-circuit current density can reach 32.6 m A cm^-2.In the end,the efficiency of Sb₂Se₃ thin-film solar cells was further improved to 7.62%,which laid a foundation for the application of Sb₂Se₃ thin-film solar cells in the Io T.(3)After a deep understanding of the mechanical properties of Sb₂Se₃ materials,a flexible Sb₂Se₃ thin-film solar cell was firstly constructed by using an ultra-thin flexible polyimide substrate,and an efficiency of 6.13%was achieved after careful optimization.The power-per-weight reached 2.04 W g^-1,comparable to that of the flexible CIGS solar cells.Due to its unique one-dimensional crystal structure,the Sb₂Se₃ solar cell remains about 97%of the initial performance after bending 1000 times under 1 mm diameter,and its flexibility is comparable to that of the organic solar cells.Related work paves the way for the application of Sb₂Se₃ thin-film solar cells in Io T.(4)The flexible Sb₂Se₃ thin-film solar mini-module was constructed by using laser processing technology and obtained a conversion efficiency of 3.03%.By further utilizing the ultra-flexibility of Sb₂Se₃ thin-film,the integration of the Sb₂Se₃ solar mini-module for the power supply of a flower monitoring system was demonstrated.Besides,the flexible Sb₂Se₃ photodetector was also explored for the wearable heart rate detection.All together,our work shows the enormous potential of flexible Sb₂Se₃ thin-film solar cells for Io T applications.