Thermophotovoltaic (TPV) system has been regarded as one promising means to alleviate current energy demand because it can directly generate electricity from radiation heat via photons.However,the presently available TPV systems suffer from low conversion efficiency and low throughput.A viable solution to increase their efficiency is to apply micro/nanoscale radiationprinciples in the design of different components to utilize the characteristics of thermal radiation at small distances and in microstructures.Several critical issues are reviewed,such as photovoltaic effect,quantum efficiency and efficiency of TPV system.Emphasis is given to the development of wavelength-selective emitters and filters and the aspects of micro/nanoscale heat transfer.Recent progress,along with the challenges and opportunities for future development of TPV systems are also outlined.