From 33% to 57% – an elevated potential of efficiency limit for indoor photovoltaics

Abstract

The limiting power conversion efficiency (PCE) defines the theoretical maximum efficiency of photovoltaic devices. The classic Shockley–Queisser method has predicted 33% for a single p–n junction solar cell under AM1.5G illumination, but those for alternative photovoltaic materials and under other illumination conditions are not well-established. The emergence of indoor photovoltaics (IPVs) generates considerable interest in this regard. Here, we explore how thin-film photovoltaic materials with different bandgaps, absorption properties, and thicknesses, perform as IPV devices. We show a material bandgap of 1.82–1.96 eV to allow a limiting 51–57% PCE for a single-junction device under various indoor illuminations. In addition, typical organic photovoltaic thin films of ∼100 nm only give limiting PCEs of merely ∼28%, but >40% for a 200–250 nm thick device making use of the second thickness peak. We also present the limiting device parameters under different illuminance, serving as a comprehensive guide for emergent IPV development. The limiting PCE and the optimal V_oc depend only weakly on the indoor light source and the domestic illuminance (100–1000 lx). In contrast, the limiting J_sc increases linearly with the illuminance (∼11–13 μA cm⁻²/100 lx). Our study offers an explicit reference for evaluating the quality of an IPV device and a guideline for future material selection for efficient IPVs.