This thesis summarises the development of the steady state and nanosecond Pump-Push-Photocurrent (PPPc) spectroscopy technique and its application to perovskite solar cells (PeSCs), focusing on the dynamic of trapped carriers from the shallow/deep and surface/bulk trap states. The main body of work was carried out on PeSCs optimised using halide substitution and surface-passivation to control the trap state density and energetics. While very few approaches are suitable to address the dynamic of trapped carriers in perovskite solar cells under working conditions, PPPc spectroscopy, provides a unique and powerful technique for tracing carrier trapping and recombination in operando optoelectronic devices.