Homogenization of optical field in nanocrystal-embedded perovskite composites

Photonic upconversion of in-band light into shorter-wavelength light has been proposed as a protocol to overcome the Shockley-Queisser (SQ) limit of photovoltaics. Many research contributions have attempted the incorporation of upconversion materials to realize this strategy. However, devising a real device with an efficiency exceeding the SQ limit still remains technically unreachable. To understand this paradoxical question, herein we use a typical upconversion nanoparticle (UCNP) with halide perovskite as a platform to quantify the UC contribution to the efficiency improvement. Our results show that the UC-induced photocurrent gain is negligible; nevertheless, the incorporation of nanomaterials even without UC capability can still enhance the photocurrent, which is related to a redistribution of the optical field and consequently a homogenization of the optical field (HOF). This can lead to a reduced photocarrier loss and provide a noticeable photocurrent enhancement (ca. 7%), which explains the general photocurrent improvement in solar cells with nanomaterials.