Suppressing Non‐Radiative Recombination via Shallow‐Level Defect Capture‐Release Mechanism in Calcium Poly(heptazine imide) for Enhanced Photocatalytic Activity

Abstract Non‐radiative recombination is a key factor restricting photocatalytic efficiency, which leads to the rapid annihilation of photogenerated carriers through deep‐level defect centers. Shallow‐level defects can suppress non‐radiative recombination through a unique carrier capture‐release mechanism. Herein, calcium poly(heptazine imide) (CaPHI) is used as a model photocatalyst to investigate the suppressing effect of shallow‐level defects on non‐radiative recombination. By regulating the concentration of shallow‐level defects, the probability of carriers being captured by deep‐level defects is reduced. As a result, the non‐radiative recombination rate decreased from 0.6361 to 0.3737 ns ⁻¹ , representing a reduction of 41.3%. The optimal CaPHI exhibits an apparent quantum efficiency of 60.57% at 420 nm for hydrogen evolution, surpassing most previously reported poly(heptazine imide) materials. This study elucidates the role of shallow‐level defects from the perspective of suppressing non‐radiative recombination, providing a new insight for addressing this issue in semiconductor photocatalysts.