From 33% to 57% – an elevated potential of efficiency limit for indoor photovoltaics†
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 Voc depend only weakly on the indoor light source and the domestic illuminance (100–1000 lx). In contrast, the limiting Jsc 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.
- This article is part of the themed collection: Journal of Materials Chemistry A HOT Papers