Device optimization by modulating carrier concentration with doping to reduce recombination losses is well known in many technologies such as c−Si solar cells [1]. In emerging photovoltaic technologies such as the halide perovskites some recent publications have discussed the effect of doping on solar cell efficiency [2–5]. Also, Feldmann et. al [6] proposed that photo−doping by bandgap variation leads to increased photoluminescence quantum efficiency Qilum which then might lead to the increase in photovoltaic efficiency.  In the current work, presented here, we aim to provide a theoretical basis for the findings of Feldmann et al. and develop models to perform a critical assessment of the role of doping on PL quantum yield and photovoltaic device performance. To tackle the different questions, we use two approaches. First, we develop a simple analytical model to study the effect of lateral band gap variations and come to the conclusion that it cannot possibly be beneficial for device performance. Then we explore doping by homogeneous concentrations of charged defects that are either always ionized (doping) or only ionized under illumination (photodoping) and describe the consequences of these two forms of doping on luminescence, charge transport and efficiency using numerical device modelling.Device optimization by modulating carrier concentration with doping to reduce recombination losses is well known in many technologies such as c−Si solar cells [1]. In emerging photovoltaic technologies such as the halide perovskites some recent publications have discussed the effect of doping on solar cell efficiency [2–5]. Also, Feldmann et. al [6] proposed that photo−doping by bandgap variation leads to increased photoluminescence quantum efficiency Qilum which then might lead to the increase in photovoltaic efficiency.  In the current work, presented here, we aim to provide a theoretical basis for the findings of Feldmann et al. and develop models to perform a critical assessment of the role of doping on PL quantum yield and photovoltaic device performance. To tackle the different questions, we use two approaches. First, we develop a simple analytical model to study the effect of lateral band gap variations and come to the conclusion that it cannot possibly be beneficial for device performance. Then we explore doping by homogeneous concentrations of charged defects that are either always ionized (doping) or only ionized under illumination (photodoping) and describe the consequences of these two forms of doping on luminescence, charge transport and efficiency using numerical device modelling.