In-situ and ex-situ Spectral Response characterization of the Radiation Damage and subsequent Recovery during Proton Irradiation of Silicon and Perovskite based Solar Cells

The dynamics of the radiation induced degradation of space solar cells is complex and often degradation and annealing are competing processes, in particular if elevated solar cell operation temperatures are reached. In-situ characterization of the degradation process during exposure of the solar cells to high energy particles can be simply performed by monitoring of the radiation-induced current, that is strongly correlated to the photoelectric properties of the solar cells. In order to detect also fast annealing processes, however, the in-situ monitoring of the photocurrent is needed. Spectrally resolved measurements of the photocurrent allow to distinct between different degradation and annealing mechanisms, like bulk effects and interface modifications, but are usually only performed ex-situ due to the bulky equipment. A very simple and compact measurement setup will be shown, that enables the spectral response measurement with good temporal resolution also in a vacuum system without the need of optical windows already during irradiation. It is based on the pointwise photocurrent generation with LEDs with different emission wavelength and a detection unit, that converts the small resulting photocurrents directly into a proportional frequency, that can then easily be monitored for example by using the audio card of a PC. First measurement during the degradation of conventional single junction monocrystalline silicon solar cells with protons are reported, confirming the good temporal resolution and the excellent signal-to-noise ratio even in the complex environment of a high energy particle accelerator. In a further evolution the setup has been modified for the characterization of Tandem type solar cells and the, in this case ex-situ, characterization of a micromorph silicon Tandem cell has been successfully demonstrated. By comparing ex-situ photocurrent spectra of these micromorph cells to the spectra of all-perovskite Tandem cells it is shown, that the micromorph cell can be used as a stable reference cell for the calibration of the in-situ setup, that will in future be used for the in-situ characterization of all-Perovskite or Perovskite/CIGS cells. These both types of Perovskite cells have been already shown to be very stable under proton irradiation. For this latter types of thin film solar cells with very promising properties for space applications the in-situ photocurrent monitoring, with excitation with a simpler two-LED irradiation system will be reported and also compared to the radiation induced current monitoring results.