Laser operation by photovoltaic features of kesterite Cu sub(2)ZnSnSe sub(x)S sub(4-x) crystalline films

We have found an enhancement of the photovoltaic efficiency from the Cu sub(2)ZnSnSe sub(x)S sub(4-x) films by illumination by the two coherent beams of 1320 nm 15 ns pulsed Nd:YAG laser. The observed changes did not exceed 10 % and were reversible. Following the performed quantum chemical simulations it was established that the origin of the effect is caused by photopolarization of the intrinsic defect trapping levels within the energy gap and photoinduced phonons. The contribution of the harmonic and anharmonic phonons was evaluated. The optimization of the photovoltaic efficiency was achieved due to the varying of Se/S ration. Additionally the pumping of the trapping intrinsic defect levels was done.