Focusing on mixed-halide Br-rich perovskite solar cells: An inevitable open-circuit voltage deficit derived from photoinduced halide segregation?

Normally, the open-circuit voltage (V_oc) of perovskite solar cells should harvest an expected increase together with bandgap widening of light absorbers. Nevertheless, the desired objective fails to be approached for Br-rich mixed-halide perovskites (MHPs), where a saturated “plateau” of V_oc distribution emerges within a bandgap range of ∼1.7 to 2.3 eV. At present, researchers agree that the photoinduced halide segregation (PIHS) issue, namely the “Hoke” effect established in 2015, is inevitably responsible for the substandard V_oc output due to photogenerated low-energy I-rich domains, but a lack of mechanism behind. Inversely, some recent advances put forward the idea that the huge V_oc deficit may directly originate from increased non-radiative recombination rather than the PIHS issue. In view of this contradictory point, we progressively study and review the cognitive process of PIHS occurrence from single MHP film to complete solar cell and then propose our perspective on the potential relationship between the PIHS issue and the device's V_oc deterioration.