Considering the continuing trend to produce low power consumption optoelectronic devices and products, self-biased semiconductor photodetectors, which convert incident photons into electrical signals without an applied voltage bias, have been a research topic of intense interest. Within this framework, the low processing cost and ease of integration have stimulated the development of various self-biased Si heterojunctions with high performance. The emergence of black silicon (b-Si) has led to the development of innovative photodiodes and solar cells. However, the external quantum efficiency (EQE) of the self-biased heterojunction photodiodes reported so far is usually significantly lower than 100% due to optical and electrical losses. The authors published their research in Advanced Science (IF 17.521). Here, the researchers propose a method to overcome the 100% EQE challenge through l low-aspect-ratio nanostructures and drift-dominated photocarrier transport in heterojunction photodiode. Broadband near-ideal EQE is achieved in nanocrystalline indium tin oxide/black silicon (nc-ITO/b-Si) Schottky photodiodes. The b-Si includes nanostalagmites that balance the antireflection effect and surface morphology. The built-in electric field is explored to match the optical generation profile to achieve enhanced photocarrier transport over a w broadband of photogeneration.

　　The article measures EQE through Enlitech QE-R quantum efficiency measurement system along with other instruments to assist in the measurement. These devices exhibit unprecedented EQE among the reported leading-edge heterojunction photodiodes:

1. The average EQE for wavelengths of 570-925 nm exceeds ≈98%, and the overall EQE from 500 to 960 nm is greater than ≈95%.
2. In addition, only elementary fabrication techniques are explored to achieve these excellent device properties. An extremely sensitive heart rate monitor driven by faint light is also demonstrated, showing the great potential of nanostalagmite b-Si heterojunction photodiode for high performance and low power consumption applications.

　　It is expected that the results of this research will pave the way for the realization of ideal b-Si integrated optoelectronic applications at a low cost.

　　In addition to the EQE (External Quantum Efficiency) spectrum analysis of solar cells, the Quantum Efficiency Measurement System of Enlitech also provides Jsc (short-circuit current density) comparison for the short-circuit current of solar cells under the solar simulator to prove the authenticity of the experiment.