  Defects are generally regarded to have negative impacts on carrier
recombination, charge-transport and ion migration in materials, which thus
lower the efficiency, speed and stability of optoelectronic devices. Meanwhile,
lots of efforts which focused on minimizing defects have greatly improved the
performances of devices. Then, can defects be positive in optoelectronic
devices? Herein, relying on in-depth understanding of defect-associated effects
in semiconductors, trapping of photo-generated carriers by defects is applied
to enlarge photoconductive gain in photodetection. Therefore, the record
photoconductive gain, gain-bandwidth product and detection limit were achieved
in this photodetector. Exceeding the general concept that defects are harmful,
we identify a new view that the defects can be positive in photodetection,
which may guide us to design high-performance photodetectors.
