1. A method comprising: supplying current to at least one photovoltaic device via a current source; transmitting only photon radiations having energy equal to a band gap of an absorber layer of the at least one photovoltaic device, from the at least one photovoltaic device to a radiation detector via an optical filter disposed between the at least one photovoltaic device and the radiation detector; detecting the emitted photon radiations from the at least one photovoltaic device via the radiation detector, outputting a signal corresponding to the detected emitted photon radiations from the radiation detector to a processor device; processing the signal corresponding to the detected emitted photon radiations via the processor device to generate one or more two-dimensional photon images; and analyzing variation in electroluminescence intensity distribution of the one or more two-dimensional photon images to determine at least one defect in the at least one photovoltaic device.