Surface repair of wide-bandgap perovskites for high-performance all-perovskite tandem solar cells

Wide-bandgap(WBG)perovskite solar cells(PSCs)play a fundamental role in perovskite-based tandem solar cells.However,the efficiency of WBG PSCs is limited by significant open-circuit voltage losses,which are primarily caused by surface defects.In this study,we present a novel method for modifying surfaces using the multifunctional S-ethylisothiourea hydrobromide(SEBr),which can passivate both Pb^(-1)and FA^(-1)terminated surfaces,Moreover,the SEBr upshifted the Fermi level at the perovskite interface,thereby promoting carrier collection.This proposed method was effective for both 1.67 and 1.77 eV WBG PSCs,achieving power conversion efficiencies(PCEs)of 22.47%and 19.90%,respectively,with V_(OC)values of 1.28 and 1.33 V,along with improved film and device stability.With this advancement,we were able to fabricate monolithic all-perovskite tandem solar cells with a champion PCE of 27.10%,This research offers valuable insights for passivating the surface trap states of WBG perovskite through rational multifunctional molecular engineering.

Experimental investigation of a novel micro gas turbine with flexible switching function for distributed power system

Micro gas turbine(MGT)is widely used in small-scale distributed power systems because of its low emissions and fuel flexibility.However,the under-utilization of its exhaust heat and the low electric efficiency are the main bottlenecks that restrict its application.Additionally,the flexible switching between the power generated by the MGT and the power grid is also a key factor for keeping the secure operation of a distributed power station.Therefore,this paper conducted some experimental investigations of a 30 kW MGT to provide reference solutions for the above issues.This MGT is located at Shanghai Jiao Tong University(SJTU),which is designed by the Gas Turbine Research Institute of SJTU,and is manufactured by a turbo machinery factory in Chongqing,China.The demonstration prototype is mainly composed of a single stage centrifugal compressor,a radial turbine,a combustor,a high-speed pennanent magnet generator,and a control system.The results show that the MGT can achieve steady operation at a low rotational speed from 10000 r/min to 34000 r/min in the case of using oil lubricated bearings,which can greatly reduce the economic cost compared with the use of air bearings.At the same time,the ignition success rate of combustion chamber(CC)reaches 98%at a low rotational speed,and a wide range of stable combustion area can be obtained,because of the novel design method of combustor by referencing the way applied in an axial flow aero-engine.The MGT generating set can achieve functions,such as starting up,ignition,stable operation,loaded operation,grid-connection and stopping.This system also can realize flexibly switching from the start motor mode to the generator mode,and from grid-connected mode to off^grid mode,because the innovative multi-state switching control system is adopted.The above research work can make our state master independent intellectual property rights of micro gas turbine,rather than continue to be subject to the technological monopoly of the developed states,which can provide theoretical and experimental support for the industrialization of MGT in China.

Performance analysis of cogeneration systems based on micro gas turbine(MGT),organic Rankine cycle and ejector refrigeration cycle

In this paper,the operation perfonnance of three novel kinds of cogeneration systems under design and off-design condition was investigated.The systems are MGT(micro gas turbine)+ORC(organic Rankine cycle)for electricity demand,MGT+ERC(ejector refrigeration cycle)for electricity and cooling demand,and MGT+ORC+ERC for electricity and cooling demand.The effect of 5 different working fluids on cogeneration systems was studied.The results show that under the design condition,when using R600 in the bottoming cycle,the MGT+ORC system has the lowest total output of 117.1 kW with a thermal efficiency of 0.334,and the MGT+ERC system has the largest total output of 142.6 kW with a thermal efficiency of 0.408.For the MGT+ORC+ERC system,the total output is between the other two systems,which is 129.3 kW with a thermal efficiency of 0.370.For the effect of different working fluids,R123 is the most suitable working fluid for MGT+ORC with the maximum electricity output power and R600 is the most suitable working fluid for MGT+ERC with the maximum cooling capacity,while both R600 and R123 can make MGT+ORC+ERC achieve a good comprehensive performance of refrigeration and electricity.The thermal efficiency of three cogeneration systems can be effectively improved under oredesign condition because the bottoming cycle can compensate for the power decrease of MGT.The results obtained in this paper can provide a reference for the design and operation of the cogeneration system for distributed energy systems(DES).