Fig. 1. Theoretical efficiency limit of indoor photovoltaics. (a)–(d) The theoretical limit of PCE, FF, V_OC, and J_SC of IPVs as a function of the band gap (E_g) under different indoor conditions at 300 K. (e) The calculated J₀ (J₀^rad, radiative recombination only at 300 K) as a function of E_g. (f) The spectra of indoor light used for the calculation (2700 and 4651 K at 1000 lux).

Fig. 2. Realistic loss analysis of J_SC. (a) The EQE_PV spectra of recently reported high-performance perovskite^[12] and organic^[28] solar cells. The blue dash lines indicate the positions of the EQE_PV of 0.7–1. (b) The integrated J_SC as a function of the different EQE_PV spectra, where EQE_PV is a step function; EQE_PV = 0.7, 0.8, 0.9, or 1 (E ≥ E_g); and EQE_PV = 0 (E < E_g). The asterisk and triangle represent the J_SC of the recently reported high-performance indoor (1000 lux) perovskite^[12] and organic^[28] photovoltaics, respectively.

Fig. 3. Realistic loss analysis of the V_OC. Plots of the V_OC limit as a function of E_g, under different nonradiative recombination. The black solid line represents the V_OC with the loss caused by only radiative recombination (without nonradiative recombination). The difference between the dash line (slope = 1) and black solid line is the loss caused by radiative recombination (ΔV^rad). The asterisk and triangle represent recently reported high-performance indoor (1000 lux) perovskite^[12] and organic^[28] photovoltaics, respectively.

Fig. 4. Realistic loss analysis of the FF. (a) The FF of the IPVs as a function of E_g when R_s is 0, 0.5, 1.0, and 2.0 Ω cm² and R_sh is 50, 100, 10³, and 10⁴ kΩ cm², respectively. The dash lines represent the FF of recently reported high-performance indoor (1000 lux) perovskite^[12] (0.84) and organic^[28] (0.811) photovoltaics, respectively. (b) The FF as a function of the resistance of the devices under indoor (2700 K, 1000 lux) illumination (R_sh) and (c) one-sun (AM 1.5G, 100 mW cm^-2) illumination (R_s). Different EQE_EL conditions were considered.

Fig. 5. Realistic loss analysis of the PCE. (a) The theoretical and experimental J-V characteristics of the IPVs. The blue line represents the theoretical limit (V_OC = 1.356 V, J_SC = 139.53 µA/cm², FF = 0.907, and PCE = 55.33% at E_g of 1.77 eV). The pink and red lines represent the realistic organic^[28] (V_OC = 0.943 V, J_SC = 123.8 µA/cm², FF = 0.811, and PCE = 30.2% at E_g of 1.72 eV) and perovskite^[12] (V_OC = 1.23 V, J_SC = 94.54 µA/cm², FF = 0.84, and PCE = 32.4% at E_g of 1.86 eV) solar cells’ curves, respectively. (b) The PCE limit as a function of E_g with different EQE_PV and EQE_EL (R_s = 0.5 Ω cm² and R_sh = 10⁴ kΩ cm²). The asterisk and triangle represent recently reported high-performance indoor (1000 lux) perovskite^[12] and organic^[28] solar cells, respectively.