Design Of Integrated Micro Solar Cell For UHF RFID Tag In Standard CMOS Technology

As an emerging wireless identification technology, radio frequency identification(RFID) technology is based on the non-contact radio frequency (RF) to communicate,automatically identify the objects and exchange dates. UHF RFID tag is the key partof the RFID system, the energy harvesting technology of UHF RFID tag has alwaysbeen concerned. In recent years, researches on the use of integrated micro solar cell topower the RFID tag have been carried out. In this paper, a CMOS compatible microsolar cell array that can be integrated with RFID tag has been developed.In the first of this paper, the UHF RFID system structure and fundamentals areanalyzed, especially the RF rectification circuit of the passive UHF RFID tag, thetechnology of using integrated solar cell to power the RFID tag is proposed. Secondly,the feasibility of manufacturing solar cell in standard CMOS technology is studied, amodel of CMOS compatible solar cell is proposed and simulated. Finally, severaldifferent size and structure of CMOS solar cells are implemented in UMC and CSMC0.18μm CMOS technology, respectively. The spectral response characteristic and theI-V characteristic of CMOS solar cells are measured. Test results show that the Seriesconnection CMOS solar cell manufactured in CSMC0.18μm CMOS technology failto output a high voltage due to substrate parasitics. The Single-stage CMOS solar cellarray with unit size of50μm×50μm manufactured in CSMC0.18μm CMOStechnology has higher efficiency than the others. The open-circuit voltage obtainedunder the conditions of AM1.5、1000W/m2、25℃is0.49V, the short-circuit currentdensity and output power density are76.61μA/mm2and29.435μW/mm2, respectively.Photoelectric conversion efficiency is2.943%.The innovation of this paper is the realization of solar cell in standard CMOStechnology.The CMOS solar cell is compatible with standard CMOS technology andcan be integrated on the same chip to power the UHF RFID tag. It will also improvethe performance of the RFID tag.The integrated solar cell technology has greatapplication prospects in the fields of RFID tag, sensor node and the internet of things.