External quantum efficiency measurements used to study the stability of differently deposited perovskite solar cells
HIERREZUELO-CARDET, PEDRO; PALECHOR-OCAMPO, ANDERZON F.; CARAM, JORGE; VENTOSINOS, FEDERICO; PÉREZ-DEL-REY, DANIEL; BOLINK, HENK J.; SCHMIDT, JAVIER A.
JOURNAL OF APPLIED PHYSICS
AMER INST PHYSICS
Lugar: New York; Año: 2020 vol. 127
The instability exhibited by perovskite solar cells when exposed to the environment under illuminationis one major obstacle for the entry of perovskite technology on the photovoltaic market. In this work, we usethe external quantum efficiency (EQE) technique to study the photoinduced degradation of two types ofsolar cells having CH3NH3PbI3 as absorber layer, one deposited by spin coating with an n-i-p architecture, andthe other deposited by evaporation with an inverted p-i-n structure. We also study the effect of differentencapsulants to protect the cells against atmospheric agents. We find that EQE provides informationregarding the areas of the cell most susceptible to degradation, in addition to providing an estimate of theoptical gap and the Urbach energy of the absorbent material. We confirm that the combined action ofillumination and the environment markedly accelerate the degradation, which is reflected in thedeterioration of all the parameters of the cell. The rear part of the cell is the first region to suffer the light-induced degradation. On the other hand, the cells deposited by evaporation and with a good encapsulationprocess are highly stable, since after 30 hours of exposure just small spectral change is noticed in thered/infrared region of the EQE spectrum.