  Despite symmetrical polarization, the magnitude of a light-induced voltage is
known to be asymmetric with respect to poling sign in many photovoltaic (PV)
ferroelectrics (FEs). This asymmetry remains unclear and is often attributed to
extrinsic effects. We show here for the first time that such an asymmetry can
be intrinsic, steaming from the superposition of asymmetries of internal FE
bias and electro-piezo-strictive deformation. This hypothesis is confirmed by
the observed decrease of PV asymmetry for smaller FE bias. Moreover, the both
PV effect and remanent polarization are found to increase under vacuum-induced
expansion and to decrease for gas-induced compression, with tens percents
tunability. The change in cations positions under pressure is analysed through
the first-principle density functional theory calculations. The reported
properties provide key insight for FE-based solar elements optimization.
